Atomic bombings of Hiroshima and Nagasaki - Wikipedia, the free encyclopedia
Thu, 19 Feb 2015 05:43
Atomic bombings of Hiroshima and NagasakiPart of the Pacific War, World War IIAtomic bomb mushroom clouds over Hiroshima (left) and Nagasaki (right)DateAugust 6 and 9, 1945LocationHiroshima and Nagasaki, JapanResultAllied victoryBelligerents United States United Kingdom JapanCommanders and leadersWilliam S. ParsonsPaul W. Tibbets, Jr.Shunroku HataUnits involvedManhattan District: 50 U.S., 2 British509th Composite Group: 1,770 U.S.Second General Army: Hiroshima: 40,000Nagasaki: 9,000Casualties and losses20 U.S., Dutch, British prisoners of war killed90,000''166,000 killed in Hiroshima39,000''80,000 killed in NagasakiTotal: 129,000''246,000+ killedIn August 1945, during the final stage of the Second World War, the United States dropped atomic bombs on the Japanese cities of Hiroshima and Nagasaki. The two bombings, which killed at least 129,000 people, remain the only use of nuclear weapons for warfare in human history.
As the Second World War entered its sixth and final year, the Allies had begun to prepare for, what was anticipated to be, a very costly invasion of the Japanese mainland. This was preceded by an immensely destructive firebombing campaign that obliterated many Japanese cities. The war in Europe had concluded when Nazi Germany signed its instrument of surrender on May 8, 1945, but with the Japanese refusal to accept the Allies' demands for unconditional surrender, the Pacific War dragged on. Together with the United Kingdom and China, the United States calls for the unconditional surrender of the Japanese armed forces in the Potsdam Declaration on July 26, 1945, was buttressed with the threat of "prompt and utter destruction".
By August 1945, the Allied Manhattan Project had successfully detonated an atomic device in the New Mexico desert and subsequently produced atomic weapons based on two alternate designs. The 509th Composite Group of the U.S. Army Air Forces was equipped with a SilverplateBoeing B-29 Superfortress that could deliver them from Tinian in the Mariana Islands. A uranium gun-type atomic bomb (Little Boy) was dropped on Hiroshima on August 6, 1945, followed by a plutonium implosion-type bomb (Fat Man) on the city of Nagasaki on August 9. Within the first two to four months of the bombings, the acute effects of the atomic bombings killed 90,000''166,000 people in Hiroshima and 39,000''80,000 in Nagasaki; roughly half of the deaths in each city occurred on the first day. During the following months, large numbers died from the effect of burns, radiation sickness, and other injuries, compounded by illness and malnutrition. In both cities, most of the dead were civilians, although Hiroshima had a sizable military garrison.
On August 15, just days after the bombing of Nagasaki and the Soviet Union's declaration of war, Japan announced its surrender to the Allies. On September 2, it signed the instrument of surrender, effectively ending World War II. The bombings' role in Japan's surrender and their ethical justification are still debated.
BackgroundPacific WarMain article: Pacific WarIn 1945, the Pacific War between the Empire of Japan and the Allies entered its fourth year. The Japanese fought fiercely, ensuring that U.S. victory would come at an enormous cost. Of the 1.25 million battle casualties incurred by the United States in World War II, including both military personnelkilled in action and wounded in action, nearly one million occurred in the twelve-month period from June 1944 to June 1945. December 1944 saw American battle casualties hit an all-time monthly high of 88,000 as a result of the German Ardennes Offensive. In the Pacific the Allies returned to the Philippines,recaptured Burma, and invaded Borneo. Offensives were undertaken to reduce the Japanese forces remaining in Bougainville, New Guinea and the Philippines. In April 1945, American forces landed on Okinawa, where heavy fighting continued until June. Along the way, the ratio of Japanese to American casualties dropped from 5:1 in the Philippines to 2:1 on Okinawa.
As the Allied advance moved inexorably towards Japan, conditions became steadily worse for the Japanese people. Japan's merchant fleet declined from 5,250,000 gross tons in 1941 to 1,560,000 tons in March 1945, and 557,000 tons in August 1945. Lack of raw materials forced the Japanese war economy into a steep decline after the middle of 1944. The civilian economy, which had slowly deteriorated throughout the war, reached disastrous levels by the middle of 1945. The loss of shipping also affected the fishing fleet, and the 1945 catch was only 22% of that in 1941. The 1945 rice harvest was the worst since 1909, and hunger and malnutrition became widespread. U.S. industrial production was overwhelmingly superior to Japan's. By 1943, the U.S, produced almost 100,000 aircraft a year, compared to Japan's production of 70,000 for the entire war. By the summer of 1944, the U.S. had almost a hundred aircraft carriers in the Pacific, far more than Japan's twenty-five for the entire war. In February 1945, Prince Fumimaro Konoe advised the EmperorHirohito that defeat was inevitable, and urged him to abdicate.
Preparations to invade JapanEven before the surrender of Nazi Germany on May 8, 1945, plans were underway for the largest operation of the Pacific War, Operation Downfall, the invasion of Japan. The operation had two parts: Operations Olympic and Coronet. Set to begin in October 1945, Olympic involved a series of landings by the U.S. Sixth Army intended to capture the southern third of the southernmost main Japanese island, KyÅshÅ. Operation Olympic was to be followed in March 1946 by Operation Coronet, the capture of the KantÅ Plain, near Tokyo on the main Japanese island of HonshÅ by the U.S. First, Eighth and Tenth Armies. The target date was chosen to allow for Olympic to complete its objectives, for troops to be redeployed from Europe, and the Japanese winter to pass.
Japan's geography made this invasion plan obvious to the Japanese; they were able to predict the Allied invasion plans accurately and thus adjust their defensive plan, Operation KetsugÅ, accordingly. The Japanese planned an all-out defense of KyÅshÅ, with little left in reserve for any subsequent defense operations. Four veteran divisions were withdrawn from the Kwantung Army in Manchuria in March 1945 to strengthen the forces in Japan, and 45 new divisions were activated between February and May 1945. Most were immobile formations for coastal defense, but 16 were high quality mobile divisions. In all, there were 2.3 million Japanese Army troops prepared to defend the home islands, backed by a civilian militia of 28 million men and women. Casualty predictions varied widely, but were extremely high. The Vice Chief of the Imperial Japanese Navy General Staff, Vice AdmiralTakijirÅ Ånishi, predicted up to 20 million Japanese deaths.
A study from June 15, 1945, by the Joint War Plans Committee, who provided planning information to the Joint Chiefs of Staff, estimated that Olympic would result in between 130,000 and 220,000 U.S. casualties of which U.S. dead would be the range from 25,000 to 46,000. Delivered on June 15, 1945, after insight gained from the Battle of Okinawa, the study noted Japan's inadequate defenses due to the very effective sea blockade and the American firebombing campaign. The Chief of Staff of the United States Army, General of the ArmyGeorge Marshall, and the Army Commander in Chief in the Pacific, General of the Army Douglas MacArthur, signed documents agreeing with the Joint War Plans Committee estimate.
The Americans were alarmed by the Japanese buildup, which was accurately tracked through Ultra intelligence.Secretary of WarHenry L. Stimson was sufficiently concerned about high American estimates of probable casualties to commission his own study by Quincy Wright and William Shockley. Wright and Shockley spoke with Colonels James McCormack and Dean Rusk, and examined casualty forecasts by Michael E. DeBakey and Gilbert Beebe. Wright and Shockley estimated the invading Allies would suffer between 1.7 and 4 million casualties in such a scenario, of whom between 400,000 and 800,000 would be dead, while Japanese casualties would have been around 5 to 10 million.
Marshall began contemplating the use of a weapon which was "readily available and which assuredly can decrease the cost in American lives":poison gas. Quantities of phosgene, mustard gas, tear gas and cyanogen chloride were moved to Luzon from stockpiles in Australia and New Guinea in preparation for Operation Olympic, and MacArthur ensured that Chemical Warfare Service units were trained in their use. Consideration was also given to using biological weapons against Japan.
Air raids on JapanWhile the United States had developed plans for an air campaign against Japan prior to the Pacific War, the capture of Allied bases in the western Pacific in the first weeks of the conflict meant that this offensive did not begin until mid-1944 when the long-ranged Boeing B-29 Superfortress became ready for use in combat.Operation Matterhorn involved India-based B-29s staging through bases around Chengdu in China to make a series of raids on strategic targets in Japan. It had failed to achieve the strategic objectives that the planners had intended, largely because of logistical problems, the bomber's mechanical difficulties, the vulnerability of Chinese staging bases, and the extreme range required to reach key Japanese cities.
United States Army Air Forces (USAAF) Brigadier GeneralHaywood S. Hansell determined that Guam, Tinian, and Saipan in the Mariana Islands would better serve as B-29 bases, but they were in Japanese hands. Strategies were shifted to accommodate the air war, and the islands were captured between June and August 1944. Air bases were developed, and B-29 operations commenced from the Marianas in October 1944. These bases were easily resupplied by cargo ships. The XXI Bomber Command began missions against Japan on November 18, 1944.
The early attempts to bomb Japan from the Marianas proved just as ineffective as the China-based B-29s had been. Hansell continued the practice of conducting so-called high-altitude precision bombing, aimed at key industries and transportation networks, even after these tactics had not produced acceptable results. These efforts proved unsuccessful due to logistical difficulties with the remote location, technical problems with the new and advanced aircraft, unfavorable weather conditions, and enemy action.
Hansell's successor, Major GeneralCurtis LeMay, assumed command in January 1945 and initially continued to use the same precision bombing tactics, with equally unsatisfactory results. The attacks initially targeted key industrial facilities but much of the Japanese manufacturing process was carried out in small workshops and private homes. Under pressure from USAAF headquarters in Washington, LeMay changed tactics and decided that low-level incendiary raids against Japanese cities were the only way to destroy their production capabilities, shifting from precision bombing to area bombardment with incendiaries.
Like most strategic bombing during World War II, the aim of the USAAF offensive against Japan was to destroy the enemy's war industries, kill or disable civilian employees of these industries, and undermine civilian morale. Civilians who took part in the war effort through such activities as building fortifications and manufacturing munitions and other war materials in factories and workshops were considered combatants in a legal sense and therefore liable to be attacked.
Over the next six months, the XXI Bomber Command under LeMay firebombed 67 Japanese cities. The firebombing of Tokyo, codenamed Operation Meetinghouse, on March 9''10 killed an estimated 100,000 people and destroyed 16 square miles (41 km2) of the city and 267,000 buildings in a single night. It was the deadliest bombing raid of the war, at a cost of 20 B-29s shot down by flak and fighters. By May, 75% of bombs dropped were incendiaries designed to burn down Japan's "paper cities". By mid-June, Japan's six largest cities had been devastated. The end of the fighting on Okinawa that month provided airfields even closer to the Japanese mainland, allowing the bombing campaign to be further escalated. Aircraft flying from Allied aircraft carriers and the Ryukyu Islands also regularly struck targets in Japan during 1945 in preparation for Operation Downfall. Firebombing switched to smaller cities, with populations ranging from 60,000 to 350,000. According to Yuki Tanaka, the U.S. fire-bombed over a hundred Japanese towns and cities. These raids were also very devastating.
The Japanese military was unable to stop the Allied attacks and the country's civil defense preparations proved inadequate. Japanese fighters and antiaircraft guns had difficulty engaging bombers flying at high altitude. From April 1945, the Japanese interceptors also had to face American fighter escorts based on Iwo Jima and Okinawa. That month, the Imperial Japanese Army Air Service and Imperial Japanese Navy Air Service stopped attempting to intercept the air raids in order to preserve fighter aircraft to counter the expected invasion. By mid-1945 the Japanese only occasionally scrambled aircraft to intercept individual B-29s conducting reconnaissance sorties over the country, in order to conserve supplies of fuel. By July 1945, the Japanese had stockpiled 1,156,000 US barrels (137,800,000 l; 36,400,000 US gal; 30,300,000 imp gal) of avgas for the invasion of Japan. While the Japanese military decided to resume attacks on Allied bombers from late June, by this time there were too few operational fighters available for this change of tactics to hinder the Allied air raids.
Atomic bomb developmentWorking in collaboration with the United Kingdom and Canada, with their respective projects Tube Alloys and Chalk River Laboratories, the Manhattan Project, under the direction of Major General Leslie R. Groves, Jr., of the U.S. Army Corps of Engineers, designed and built the first atomic bombs.
The uranium atom was first split by German physicists in 1938, making the development of an atomic bomb a theoretical possibility. Fearing that the German atomic bomb project would develop atomic weapons first, preliminary research in the U.S. began in late 1939. Progress was slow until the arrival of the British MAUD Committee report in late 1941 showed that only 5-10 kilograms, and not 500 tons, of pure uranium were needed. Arthur H. Compton set up the Metallurgical Laboratory in Chicago, where, on December 2, 1942 the first sustained nuclear chain reaction was achieved. Groves appointed J. Robert Oppenheimer to orgainse and head the project's Los Alamos Laboratory in New Mexico.
Two types of bombs were eventually devised. The Hiroshima bomb, known as a Little Boy, was a gun-type fission weapon that used uranium-235, a rare isotope of uranium extracted in giant factories at Oak Ridge, Tennessee. The other was a more powerful and efficient but more complicated implosion-type nuclear weapon using plutonium-239, a synthetic element created in nuclear reactors at Hanford, Washington. A test implosion weapon, the gadget, was detonated at Trinity Site, on July 16, 1945, near Alamogordo, New Mexico. The Nagasaki bomb, a Fat Man, was a similar device.
There was a Japanese nuclear weapon program, but it lacked the human, mineral and financial resources of the Manhattan Project, and never made much progress towards developing an atomic bomb.
PreparationsOrganization and trainingThe 509th Composite Group was constituted on December 9, 1944, and activated on December 17, 1944, at Wendover Army Air Field, Utah, commanded by ColonelPaul Tibbets. Tibbets was assigned to organize and command a combat group to develop the means of delivering an atomic weapon against targets in Germany and Japan. Because the flying squadrons of the group consisted of both bomber and transport aircraft, the group was designated as a "composite" rather than a "bombardment" unit.
Working with the Manhattan Project at Los Alamos, Tibbets selected Wendover for his training base over Great Bend, Kansas, and Mountain Home, Idaho, because of its remoteness. Each bombardier completed at least 50 practice drops of inert or conventional explosive pumpkin bombs and Tibbets declared his group combat-ready.
The 509th Composite Group had an authorized strength of 225 officers and 1,542 enlisted men, almost all of whom eventually deployed to Tinian. In addition to its authorized strength, the 509th had attached to it on Tinian 51 civilian and military personnel from Project Alberta, known as the 1st Technical Detachment. The 509th Composite Group's 393d Bombardment Squadron was equipped with 15 Silverplate B-29s. These aircraft were specially adapted to carry nuclear weapons, and were equipped with fuel-injected engines, Curtiss Electric reversible-pitchpropellers, pneumatic actuators for rapid opening and closing of bomb bay doors and other improvements.
The ground support echelon of the 509th Composite Group moved by rail on April 26, 1945, to its port of embarkation at Seattle, Washington. On May 6 the support elements sailed on the SS Cape Victory for the Marianas, while group materiel was shipped on the SS Emile Berliner. The Cape Victory made brief port calls at Honolulu and Eniwetok but the passengers were not permitted to leave the dock area. An advance party of the air echelon, consisting of 29 officers and 61 enlisted men flew by C-54 to North Field on Tinian, between May 15 and 22.
There were also two representatives from Washington, D.C., Brigadier GeneralThomas Farrell, the deputy commander of the Manhattan Project, and Rear AdmiralWilliam R. Purnell of the Military Policy Committee, who were on hand to decide higher policy matters on the spot. Along with Captain William S. Parsons, the commander of Project Alberta, they became known as the "Tinian Joint Chiefs".
Choice of targetsIn April 1945, Marshall asked Groves to nominate specific targets for bombing for final approval by himself and Stimson. Groves formed a Target Committee chaired by himself, that included Farrell, Major John A. Derry, Colonel William P. Fisher, Joyce C. Stearns and David M. Dennison from the USAAF; and scientists John von Neumann, Robert R. Wilson and William Penney from the Manhattan Project. The Target Committee met in Washington on April 27; at Los Alamos on May 10, where it was able to talk to the scientists and technicians there; and finally in Washington on May 28, where it was briefed by Tibbets and CommanderFrederick Ashworth from Project Alberta, and the Manhattan Project's scientific advisor, Richard C. Tolman.
The Target Committee nominated five targets: Kokura, the site of one of Japan's largest munitions plants; Hiroshima, an embarkation port and industrial center that was the site of a major military headquarters; Yokohama, an urban center for aircraft manufacture, machine tools, docks, electrical equipment and oil refineries; Niigata, a port with industrial facilities including steel and aluminum plants and an oil refinery; and Kyoto, a major industrial center. The target selection was subject to the following criteria:
The target was larger than 3 mi (4.8 km) in diameter and was an important target in a large urban area.The blast would create effective damage.The target was unlikely to be attacked by August 1945.These cities were largely untouched during the nightly bombing raids and the Army Air Forces agreed to leave them off the target list so accurate assessment of the weapon could be made. Hiroshima was described as "an important army depot and port of embarkation in the middle of an urban industrial area. It is a good radar target and it is such a size that a large part of the city could be extensively damaged. There are adjacent hills which are likely to produce a focusing effect which would considerably increase the blast damage. Due to rivers it is not a good incendiary target."
The Target Committee stated that "It was agreed that psychological factors in the target selection were of great importance. Two aspects of this are (1) obtaining the greatest psychological effect against Japan and (2) making the initial use sufficiently spectacular for the importance of the weapon to be internationally recognized when publicity on it is released. Kyoto had the advantage of being an important center for military industry, as well an intellectual center and hence a population better able to appreciate the significance of the weapon. The Emperor's palace in Tokyo has a greater fame than any other target but is of least strategic value."
Edwin O. Reischauer, a Japan expert for the U.S. Army Intelligence Service, was incorrectly said to have prevented the bombing of Kyoto. In his autobiography, Reischauer specifically refuted this claim:
... the only person deserving credit for saving Kyoto from destruction is Henry L. Stimson, the Secretary of War at the time, who had known and admired Kyoto ever since his honeymoon there several decades earlier.
On May 30, Stimson asked Groves to remove Kyoto from the target list, but Groves pointed to its military and industrial significance. Stimson then approached PresidentHarry S. Truman about the matter. Truman agreed with Stimson, and Kyoto was temporarily removed from the target list. Groves attempted to restore Kyoto to the target list in July, but Stimson remained adamant. On July 25, Nagasaki was put on the target list in place of Kyoto. Orders for the attack were issued to General Carl Spaatz on July 25 under the signature of General Thomas T. Handy, the acting Chief of Staff, since Marshall was at the Potsdam Conference with Truman. That day, Truman noted in his diary that:
This weapon is to be used against Japan between now and August 10th. I have told the Sec. of War, Mr. Stimson, to use it so that military objectives and soldiers and sailors are the target and not women and children. Even if the Japs are savages, ruthless, merciless and fanatic, we as the leader of the world for the common welfare cannot drop that terrible bomb on the old capital [Kyoto] or the new [Tokyo]. He and I are in accord. The target will be a purely military one.
Proposed demonstrationIn early May 1945, the Interim Committee was created by Stimson at the urging of leaders of the Manhattan Project and with the approval of Truman to advise on matters pertaining to nuclear energy. During the meetings on May 31 and June 1, scientist Ernest Lawrence had suggested giving the Japanese a non-combat demonstration.Arthur Compton later recalled that:
It was evident that everyone would suspect trickery. If a bomb were exploded in Japan with previous notice, the Japanese air power was still adequate to give serious interference. An atomic bomb was an intricate device, still in the developmental stage. Its operation would be far from routine. If during the final adjustments of the bomb the Japanese defenders should attack, a faulty move might easily result in some kind of failure. Such an end to an advertised demonstration of power would be much worse than if the attempt had not been made. It was now evident that when the time came for the bombs to be used we should have only one of them available, followed afterwards by others at all-too-long intervals. We could not afford the chance that one of them might be a dud. If the test were made on some neutral territory, it was hard to believe that Japan's determined and fanatical military men would be impressed. If such an open test were made first and failed to bring surrender, the chance would be gone to give the shock of surprise that proved so effective. On the contrary, it would make the Japanese ready to interfere with an atomic attack if they could. Though the possibility of a demonstration that would not destroy human lives was attractive, no one could suggest a way in which it could be made so convincing that it would be likely to stop the war.
The possibility of a demonstration was raised again in the Franck Report issued by physicist James Franck on June 11 and the Scientific Advisory Panel rejected his report on June 16, saying that "we can propose no technical demonstration likely to bring an end to the war; we see no acceptable alternative to direct military use." Franck then took the report to Washington, D.C., where the Interim Committee met on June 21 to re-examine its earlier conclusions; but it reaffirmed that there was no alternative to the use of the bomb on a military target.
Like Compton, many U.S. officials and scientists argued that a demonstration would sacrifice the shock value of the atomic attack, and the Japanese could deny the atomic bomb was lethal, making the mission less likely to produce surrender. Allied prisoners of war might be moved to the demonstration site and be killed by the bomb. They also worried that the bomb might be a dud since the Trinity test was of a stationary device, not an air-dropped bomb. In addition, only two bombs would be available at the start of August, although more were in production, and they cost billions of dollars, so using one for a demonstration would be expensive.
LeafletsFor several months, the U.S. had dropped more than 63 million leaflets across Japan warning civilians of air raids. Many Japanese cities suffered terrible damage from aerial bombings, some were as much as 97% destroyed. LeMay thought that this would increase the psychological impact of bombing, and reduce the stigma of area bombing cities. Even with the warnings, Japanese opposition to the war remained ineffective. In general, the Japanese regarded the leaflet messages as truthful, but anyone who was caught in possession of one was arrested. Leaflet texts were prepared by recent Japanese prisoners of war because they were thought to be the best choice "to appeal to their compatriots".
In preparation for dropping an atomic bomb on Hiroshima, U.S. military leaders decided against a demonstration bomb, and against a special leaflet warning, in both cases because of the uncertainty of a successful detonation, and the wish to maximize psychological shock. No warning was given to Hiroshima that a new and much more destructive bomb was going to be dropped. Various sources give conflicting information about when the last leaflets were dropped on Hiroshima prior to the atomic bomb. Robert Jay Lifton writes that it was July 27, and Theodore H. McNelly that it was July 3. The USAAF history notes eleven cities were targeted with leaflets on July 27, but Hiroshima was not one of them, and there were no leaflet sorties on July 30. Leaflet sorties were undertaken on August 1 and 4. It is very likely that Hiroshima was leafleted in late July or early August, as survivor accounts talk about a delivery of leaflets a few days before the atomic bomb was dropped. One such leaflet lists twelve cities targeted for firebombing: Otaru, Akita, Hachinohe, Fukushima, Urawa, Takayama, Iwakuni, Tottori, Imabari, Yawata, Miyakonojo, and Saga. Hiroshima was not listed.
Potsdam DeclarationTruman delayed the start of the summit by two weeks in the hope that the bomb could be tested before the start of negotiations with Stalin. The Trinity Test of July 16 exceeded expectations. On July 26, Allied leaders issued the Potsdam Declaration outlining terms of surrender for Japan. It was presented as an ultimatum and stated that without a surrender, the Allies would attack Japan, resulting in "the inevitable and complete destruction of the Japanese armed forces and just as inevitably the utter devastation of the Japanese homeland". The atomic bomb was not mentioned in the communiqu(C). On July 28, Japanese papers reported that the declaration had been rejected by the Japanese government. That afternoon, Prime MinisterSuzuki KantarÅ declared at a press conference that the Potsdam Declaration was no more than a rehash (yakinaoshi) of the Cairo Declaration and that the government intended to ignore it (mokusatsu, "kill by silence"). The statement was taken by both Japanese and foreign papers as a clear rejection of the declaration. Emperor Hirohito, who was waiting for a Soviet reply to non-committal Japanese peace feelers, made no move to change the government position.
Under the 1943 Quebec Agreement with the United Kingdom, the United States had agreed that nuclear weapons would not be used against another country without mutual consent. In June 1945 the head of the British Joint Staff Mission, Field Marshal Sir Henry Maitland Wilson, agreed that the use of nuclear weapons against Japan would be officially recorded as a decision of the Combined Policy Committee. At Potsdam, Truman agreed to a request from Winston Churchill that Britain be represented when the atomic bomb was dropped. William Penney and Group CaptainLeonard Cheshire were sent to Tinian, but found that LeMay would not let them accompany the mission. All they could do was send a strongly worded signal back to Wilson.
BombsThe Little Boy bomb, except for the uranium payload, was ready at the beginning of May 1945. The uranium-235 projectile was completed on June 15, and the target on July 24. The target and bomb pre-assemblies (partly assembled bombs without the fissile components) left Hunters Point Naval Shipyard, California, on July 16 aboard the cruiserUSS Indianapolis, arriving July 26. The target inserts followed by air on July 30.
The first plutonium core, along with its polonium-berylliumurchin initiator, was transported in the custody of Project Alberta courier Raemer Schreiber in a magnesium field carrying case designed for the purpose by Philip Morrison. Magnesium was chosen because it does not act as a tamper. The core departed from Kirtland Army Air Field on a C-54 transport aircraft of the 509th Composite Group's 320th Troop Carrier Squadron on July 26, and arrived at North Field July 28. Three Fat Man high-explosive pre-assemblies, designated F31, F32, and F33, were picked up at Kirtland on July 28 by three B-29s, from the 393d Bombardment Squadron, plus one from the 216th Army Air Force Base Unit, and transported to North Field, arriving on August 2.
HiroshimaHiroshima during World War IIAt the time of its bombing, Hiroshima was a city of both industrial and military significance. A number of military units were located nearby, the most important of which was the headquarters of Field MarshalShunroku Hata's Second General Army, which commanded the defense of all of southern Japan, and was located in Hiroshima Castle. Hata's command consisted of some 400,000 men, most of whom were on Kyushu where an Allied invasion was correctly anticipated. Also present in Hiroshima were the headquarters of the 59th Army, the 5th Division and the 224th Division, a recently formed mobile unit. The city was defended by five batteries of 7-and-8-centimeter (2.8 and 3.1 in) anti-aircraft guns of the 3rd Anti-Aircraft Division, including units from the 121st and 122nd Anti-Aircraft Regiments and the 22nd and 45th Separate Anti-Aircraft Battalions. In total, over 40,000 military personnel were stationed in the city.
Hiroshima was a minor supply and logistics base for the Japanese military, but it also had large stockpiles of military supplies. The city was a communications center, a key port for shipping and an assembly area for troops. It was also the second largest city in Japan after Kyoto that was still undamaged by air raids, due to the fact that it lacked the aircraft manufacturing industry that was the XXI Bomber Command's priority target. On July 3, the Joint Chiefs of Staff placed it off limits to bombers, along with Kokura, Niigata and Kyoto.
The center of the city contained several reinforced concrete buildings and lighter structures. Outside the center, the area was congested by a dense collection of small wooden workshops set among Japanese houses. A few larger industrial plants lay near the outskirts of the city. The houses were constructed of wood with tile roofs, and many of the industrial buildings were also built around wood frames. The city as a whole was highly susceptible to fire damage.
The population of Hiroshima had reached a peak of over 381,000 earlier in the war but prior to the atomic bombing, the population had steadily decreased because of a systematic evacuation ordered by the Japanese government. At the time of the attack, the population was approximately 340,000''350,000. Residents wondered why Hiroshima had been spared destruction by firebombing. Some speculated that the city was to be saved for U.S. occupation headquarters, others thought perhaps their relatives in Hawaii and California had petitioned the U.S. government to avoid bombing Hiroshima. More realistic city officials had ordered buildings torn down to create long, straight firebreaks, beginning in 1944. Firebreaks continued to be expanded and extended up to the morning of August 6, 1945.
The bombingHiroshima was the primary target of the first nuclear bombing mission on August 6, with Kokura and Nagasaki as alternative targets. The 393d Bombardment Squadron B-29 Enola Gay, piloted by Tibbets, took off from North Field, Tinian, about six hours' flight time from Japan. The Enola Gay (named after Tibbets' mother) was accompanied by two other B-29s. The Great Artiste, commanded by Major Charles Sweeney, carried instrumentation, and a then-nameless aircraft later called Necessary Evil, commanded by Captain George Marquardt, served as the photography aircraft.
After leaving Tinian the aircraft made their way separately to Iwo Jima to rendezvous with Sweeney and Marquardt at 05:55 at 9,200 feet (2,800 m), and set course for Japan. The aircraft arrived over the target in clear visibility at 31,060 feet (9,470 m). Parsons, who was in command of the mission, armed the bomb during the flight to minimize the risks during takeoff. He had witnessed four B-29s crash and burn at takeoff, and feared that a nuclear explosion would occur if a B-29 crashed with an armed Little Boy on board. His assistant, Second LieutenantMorris R. Jeppson, removed the safety devices 30 minutes before reaching the target area.
During the night of August 5''6, Japanese early warning radar detected the approach of numerous American aircraft headed for the southern part of Japan. Radar detected 65 bombers headed for Saga, 102 bound for Maebashi, 261 en route to Nishinomiya, 111 headed for Ube and 66 bound for Imabari. An alert was given and radio broadcasting stopped in many cities, among them Hiroshima. The all-clear was sounded in Hiroshima at 00:05. About an hour before the bombing, the air raid alert was sounded again, as Straight Flush flew over the city. It broadcast a short message which was picked up by Enola Gay. It read: "Cloud cover less than 3/10th at all altitudes. Advice: bomb primary." The all-clear was sounded over Hiroshima again at 07:09.
At 08:09 Tibbets started his bomb run and handed control over to his bombardier, Major Thomas Ferebee. The release at 08:15 (Hiroshima time) went as planned, and the Little Boy containing about 64 kg (141 lb) of uranium-235 took 44.4 seconds to fall from the aircraft flying at about 31,000 feet (9,400 m) to a detonation height of about 1,900 feet (580 m) above the city.Enola Gay traveled 11.5 mi (18.5 km) before it felt the shock waves from the blast.
Due to crosswind, the bomb missed the aiming point, the Aioi Bridge, by approximately 800 ft (240 m) and detonated directly over Shima Surgical Clinic at 34°23'²41'"N132°27'²17'"E>> / >>34.39468°N 132.45462°E>> / 34.39468; 132.45462. It created a blast equivalent to 16 kilotons of TNT (67 TJ), ± 2 kt. The weapon was considered very inefficient, with only 1.7% of its material fissioning. The radius of total destruction was about 1 mile (1.6 km), with resulting fires across 4.4 square miles (11 km2).
People on the ground reported seeing a pika or brilliant flash of light followed by a don, a loud booming sound. Some 70,000''80,000 people, of whom 20,000 were soldiers, or around 30% of the population of Hiroshima, were killed by the blast and resultant firestorm, and another 70,000 injured.
Events on the groundSome of the reinforced concrete buildings in Hiroshima had been very strongly constructed because of the earthquake danger in Japan, and their framework did not collapse even though they were fairly close to the blast center. Since the bomb detonated in the air, the blast was directed more downward than sideways, which was largely responsible for the survival of the Prefectural Industrial Promotional Hall, now commonly known as the Genbaku (A-bomb) dome. This building was designed and built by the Czech architect Jan Letzel, and was only 150 m (490 ft) from ground zero. The ruin was named Hiroshima Peace Memorial and was made a UNESCO World Heritage Site in 1996 over the objections of the United States and China, which expressed reservations on the grounds that other Asian nations were the ones who suffered the greatest loss of life and property, and a focus on Japan lacked historical perspective.
The Americans estimated that 4.7 square miles (12 km2) of the city were destroyed. Japanese officials determined that 69% of Hiroshima's buildings were destroyed and another 6''7% damaged. The bombing started fires that spread rapidly through wood and paper homes. As in other Japanese cities, the firebreaks proved ineffective.
Hiroshima bombingStrike order for the Hiroshima bombing as posted on August 5, 1945
Injured civilian casualties
The dark portions of the garments this victim wore during the flash caused burns on the skin
EizÅ Nomura was the closest known survivor, who was in the basement of a reinforced concrete building (it remained as the Rest House after the war) only 170 metres (560 ft) from ground zero (the hypocenter) at the time of the attack. He lived into his 80s. Akiko Takakura was among the closest survivors to the hypocenter of the blast. She had been in the solidly built Bank of Hiroshima only 300 meters (980 ft) from ground-zero at the time of the attack.
Over 90% of the doctors and 93% of the nurses in Hiroshima were killed or injured'--most had been in the downtown area which received the greatest damage. The hospitals were destroyed or heavily damaged. Only one doctor, Terufumi Sasaki, remained on duty at the Red Cross Hospital. Nonetheless, by early afternoon, the police and volunteers had established evacuation centres at hospitals, schools and tram stations, and a morgue was established in the Asano library.
Most elements of the Japanese Second General Army headquarters were at physical training on the grounds of Hiroshima Castle, barely 900 yards (820 m) from the hypocenter. The attack killed 3,243 troops on the parade ground. The communications room of Chugoku Military District Headquarters that was responsible for issuing and lifting air raid warnings was in a semi-basement in the castle. Yoshie Oka, a Hijiyama Girls High School student who had been mobilized to serve as a communications officer had just sent a message that the alarm had been issued for Hiroshima and Yamaguchi when the bomb exploded. She used a special phone to inform Fukuyama Headquarters that "Hiroshima has been attacked by a new type of bomb. The city is in a state of near-total destruction."
Since Mayor Senkichi Awaya had been killed while eating breakfast with his son and granddaughter at the mayoral residence, Field Marshal Hata, who was only slightly wounded, took over the administration of the city, and coordinated relief efforts. Many of his staff had been killed or fatally wounded, including a Korean prince of the Joseon Dynasty, Yi Wu, who was serving as a lieutenant colonel in the Japanese Army. Hata's senior surviving staff officer was the wounded Colonel Kumao Imoto, who acted as his chief of staff. Hiroshima Ujina Harbor was undamaged, and soldiers from there used suicide boats intended to repel the American invasion to collect the wounded, and take them down the rivers to the military hospital at Ujina. Trucks and trains brought in relief supplies and evacuated survivors from the city.
Twelve American airmen were imprisoned at the Chugoku Military Police Headquarters located about 1,300 feet (400 m) from the hypocenter of the blast. Most died instantly, although two were reported to have been executed by their captors, and two prisoners badly injured by the bombing were left next to the Aioi Bridge by the Kempei Tai, where they were stoned to death.
Japanese realization of the bombingHiroshima before the bombing.
Hiroshima after the bombing.
The Tokyo control operator of the Japan Broadcasting Corporation noticed that the Hiroshima station had gone off the air. He tried to re-establish his program by using another telephone line, but it too had failed. About 20 minutes later the Tokyo railroad telegraph center realized that the main line telegraph had stopped working just north of Hiroshima. From some small railway stops within 16 km (9.9 mi) of the city came unofficial and confused reports of a terrible explosion in Hiroshima. All these reports were transmitted to the headquarters of the Imperial Japanese Army General Staff.
Military bases repeatedly tried to call the Army Control Station in Hiroshima. The complete silence from that city puzzled the General Staff; they knew that no large enemy raid had occurred and that no sizable store of explosives was in Hiroshima at that time. A young officer was instructed to fly immediately to Hiroshima, to land, survey the damage, and return to Tokyo with reliable information for the staff. It was felt that nothing serious had taken place and that the explosion was just a rumor.
The staff officer went to the airport and took off for the southwest. After flying for about three hours, while still nearly 160 km (99 mi) from Hiroshima, he and his pilot saw a great cloud of smoke from the bomb. In the bright afternoon, the remains of Hiroshima were burning. Their plane soon reached the city, around which they circled in disbelief. A great scar on the land still burning and covered by a heavy cloud of smoke was all that was left. They landed south of the city, and the staff officer, after reporting to Tokyo, began to organize relief measures.
Events of August 7''9After the Hiroshima bombing, Truman issued a statement announcing the use of the new weapon. He stated, "We may be grateful to Providence" that the German atomic bomb project had failed, and that the United States and its allies had "spent two billion dollars on the greatest scientific gamble in history'--and won." Truman then warned Japan: "If they do not now accept our terms, they may expect a rain of ruin from the air, the like of which has never been seen on this earth. Behind this air attack will follow sea and land forces in such numbers and power as they have not yet seen and with the fighting skill of which they are already well aware."
The Japanese government did not react. Emperor Hirohito, the government, and the war council considered four conditions for surrender: the preservation of the kokutai (Imperial institution and national polity), assumption by the Imperial Headquarters of responsibility for disarmament and demobilization, no occupation of the Japanese Home Islands, Korea, or Formosa, and delegation of the punishment of war criminals to the Japanese government.
The Soviet Foreign Minister Vyacheslav Molotov informed Tokyo of the Soviet Union's unilateral abrogation of the Soviet''Japanese Neutrality Pact on August 5. At two minutes past midnight on August 9, Tokyo time, Soviet infantry, armor, and air forces had launched the Manchurian Strategic Offensive Operation. Four hours later, word reached Tokyo of the Soviet Union's official declaration of war. The senior leadership of the Japanese Army began preparations to impose martial law on the nation, with the support of Minister of War Korechika Anami, in order to stop anyone attempting to make peace.
On August 7, a day after Hiroshima was destroyed, Dr. Yoshio Nishina and other atomic physicists arrived at the city, and carefully examined the damage. They then went back to Tokyo and told the cabinet that Hiroshima was indeed destroyed by an atomic bomb. Admiral Soemu Toyoda, the Chief of the Naval General Staff, estimated that no more than one or two additional bombs could be readied, so they decided to endure the remaining attacks, acknowledging "there would be more destruction but the war would go on." American Magic codebreakers intercepted the cabinet's messages.
Purnell, Parsons, Tibbets, Spaatz, and LeMay met on Guam that same day to discuss what should be done next. Since there was no indication of Japan surrendering, they decided to proceed with dropping another bomb. Parsons said that Project Alberta would have it ready by August 11, but Tibbets pointed to weather reports indicating poor flying conditions on that day due to a storm, and asked if the bomb could be readied by August 9. Parsons agreed to try to do so.
NagasakiI realize the tragic significance of the atomic bomb ... It is an awful responsibility which has come to us ... We thank God that it has come to us, instead of to our enemies; and we pray that He may guide us to use it in His ways and for His purposes.
Nagasaki during World War IIThe city of Nagasaki had been one of the largest seaports in southern Japan, and was of great wartime importance because of its wide-ranging industrial activity, including the production of ordnance, ships, military equipment, and other war materials. The four largest companies in the city were Mitsubishi Shipyards, Electrical Shipyards, Arms Plant, and Steel and Arms Works, which employed about 90% of the city's labor force, and accounted for 90% of the city's industry. Although an important industrial city, Nagasaki had been spared from firebombing because its geography made it difficult to locate at night with AN/APQ-13 radar.
Unlike the other target cities, Nagasaki had not been placed off limits to bombers by the Joint Chiefs of Staff's July 3 directive, and was bombed on a small scale five times. During one of these raids on August 1, a number of conventional high-explosive bombs were dropped on the city. A few hit the shipyards and dock areas in the southwest portion of the city, and several hit the Mitsubishi Steel and Arms Works. By early August, the city was defended by the IJA 134th Anti-Aircraft Regiment of the 4th Anti-Aircraft Division with four batteries of 7 cm (2.8 in) anti-aircraft guns and two searchlight batteries.
In contrast to Hiroshima, almost all of the buildings were of old-fashioned Japanese construction, consisting of wood or wood-frame buildings with wood walls (with or without plaster) and tile roofs. Many of the smaller industries and business establishments were also situated in buildings of wood or other materials not designed to withstand explosions. Nagasaki had been permitted to grow for many years without conforming to any definite city zoning plan; residences were erected adjacent to factory buildings and to each other almost as closely as possible throughout the entire industrial valley. On the day of the bombing, an estimated 263,000 people were in Nagasaki, including 240,000 Japanese residents, 10,000 Korean residents, 2,500 conscripted Korean workers, 9,000 Japanese soldiers, 600 conscripted Chinese workers, and 400 Allied prisoners of war in a camp to the north of Nagasaki.
The bombingResponsibility for the timing of the second bombing was delegated to Tibbets. Scheduled for August 11 against Kokura, the raid was moved earlier by two days to avoid a five-day period of bad weather forecast to begin on August 10. Three bomb pre-assemblies had been transported to Tinian, labeled F-31, F-32, and F-33 on their exteriors. On August 8, a dress rehearsal was conducted off Tinian by Sweeney using Bockscar as the drop airplane. Assembly F-33 was expended testing the components and F-31 was designated for the August 9 mission.
Special Mission 16, Secondary target Nagasaki, August 9, 1945AircraftPilotCall SignMission roleEnola GayCaptain George W. MarquardtDimples 82Weather reconnaissance (Kokura)Laggin' DragonCaptain Charles F. McKnightDimples 95Weather reconnaissance (Nagasaki)BockscarMajor Charles W. SweeneyDimples 77Weapon DeliveryThe Great ArtisteCaptain Frederick C. BockDimples 89Blast measurement instrumentationBig StinkMajor James I. Hopkins, Jr.Dimples 90Strike observation and photographyFull HouseMajor Ralph R. TaylorDimples 83Strike spare'--did not complete missionAt 03:49 on the morning of August 9, 1945, Bockscar, flown by Sweeney's crew, carried Fat Man, with Kokura as the primary target and Nagasaki the secondary target. The mission plan for the second attack was nearly identical to that of the Hiroshima mission, with two B-29s flying an hour ahead as weather scouts and two additional B-29s in Sweeney's flight for instrumentation and photographic support of the mission. Sweeney took off with his weapon already armed but with the electrical safety plugs still engaged.
During pre-flight inspection of Bockscar, the flight engineer notified Sweeney that an inoperative fuel transfer pump made it impossible to use 640 US gallons (2,400 l; 530 imp gal) of fuel carried in a reserve tank. This fuel would still have to be carried all the way to Japan and back, consuming still more fuel. Replacing the pump would take hours; moving the Fat Man to another aircraft might take just as long and was dangerous as well, as the bomb was live. Tibbets and Sweeney therefore elected to have Bockscar continue the mission.
This time Penney and Cheshire were allowed to accompany the mission, flying as observers on the third plane, Big Stink, flown by the group's operations officer, Major James I. Hopkins, Jr. Observers aboard the weather planes reported both targets clear. When Sweeney's aircraft arrived at the assembly point for his flight off the coast of Japan, Big Stink failed to make the rendezvous. According to Cheshire, Hopkins was at varying heights including 9,000 feet (2,700 m) higher than he should have been, and was not flying tight circles over Yakushima as previously agreed with Sweeney and Captain Frederick C. Bock, who was piloting the support B-29 The Great Artiste. Instead, Hopkins was flying 40-mile (64 km) dogleg patterns. Though ordered not to circle longer than fifteen minutes, Sweeney continued to wait for Big Stink, at the urging of Ashworth, the plane's weaponeer, who was in command of the mission.
After exceeding the original departure time limit by a half hour, Bockscar, accompanied by The Great Artiste, proceeded to Kokura, thirty minutes away. The delay at the rendezvous had resulted in clouds and drifting smoke from fires started by a major firebombing raid by 224 B-29s on nearby Yahata the previous day over Kokura. Additionally, the Yawata Steel Works intentionally burned coal tar, to produce black smoke. The clouds and smoke resulted in 70% of the area over Kokura being covered, obscuring the aiming point. Three bomb runs were made over the next 50 minutes, burning fuel and exposing the aircraft repeatedly to the heavy defenses of Yawata, but the bombardier was unable to drop visually. By the time of the third bomb run, Japanese antiaircraft fire was getting close, and Second Lieutenant Jacob Beser, who was monitoring Japanese communications, reported activity on the Japanese fighter direction radio bands.
After three runs over the city, and with fuel running low because of the failed fuel pump, they headed for their secondary target, Nagasaki. Fuel consumption calculations made en route indicated that Bockscar had insufficient fuel to reach Iwo Jima and would be forced to divert to Okinawa. After initially deciding that if Nagasaki were obscured on their arrival the crew would carry the bomb to Okinawa and dispose of it in the ocean if necessary, Ashworth ruled that a radar approach would be used if the target was obscured.
At about 07:50 Japanese time, an air raid alert was sounded in Nagasaki, but the "all clear" signal was given at 08:30. When only two B-29 Superfortresses were sighted at 10:53, the Japanese apparently assumed that the planes were only on reconnaissance and no further alarm was given.
A few minutes later at 11:00, The Great Artiste dropped instruments attached to three parachutes. These instruments also contained an unsigned letter to Professor Ryokichi Sagane, a physicist at the University of Tokyo who studied with three of the scientists responsible for the atomic bomb at the University of California, Berkeley, urging him to tell the public about the danger involved with these weapons of mass destruction. The messages were found by military authorities but not turned over to Sagane until a month later. In 1949, one of the authors of the letter, Luis Alvarez, met with Sagane and signed the document.
At 11:01, a last-minute break in the clouds over Nagasaki allowed Bockscar's bombardier, Captain Kermit Beahan, to visually sight the target as ordered. The Fat Man weapon, containing a core of about 6.4 kg (14 lb) of plutonium, was dropped over the city's industrial valley at 32°46'²25'"N129°51'²48'"E>> / >>32.77372°N 129.86325°E>> / 32.77372; 129.86325. It exploded 47 seconds later at 1,650 ± 33 ft (503 ± 10 m), above a tennis court halfway between the Mitsubishi Steel and Arms Works in the south and the Mitsubishi-Urakami Ordnance Works (Torpedo Works) in the north. This was nearly 3 km (1.9 mi) northwest of the planned hypocenter; the blast was confined to the Urakami Valley and a major portion of the city was protected by the intervening hills. The resulting explosion had a blast yield equivalent to 21 ± 2 kt (87.9 ± 8.4 TJ). The explosion generated heat estimated at 3,900 °C (7,050 °F) and winds that were estimated at 1,005 km/h (624 mph).
Big Stink spotted the explosion from a hundred miles away, and flew over to observe. Because of the delays in the mission and the inoperative fuel transfer pump, Bockscar did not have sufficient fuel to reach the emergency landing field at Iwo Jima, so Sweeney and Bock flew to Okinawa. Arriving there, Sweeney circled for 20 minutes trying to contact the control tower for landing clearance, finally concluding that his radio was faulty. Critically low on fuel, Bockscar barely made it to the runway on Okinawa's Yontan Airfield. With only enough fuel for one landing attempt, Sweeney and Albury brought Bockscar in at 150 miles per hour (240 km/h) instead of the normal 120 miles per hour (190 km/h), firing distress flares to alert the field of the uncleared landing. The number two engine died from fuel starvation as Bockscar began its final approach. Touching the runway hard, the heavy B-29 slewed left and towards a row of parked B-24 bombers before the pilots managed to regain control. The B-29's reversible propellers were insufficient to slow the aircraft adequately, and with both pilots standing on the brakes, Bockscar made a swerving 90-degree turn at the end of the runway to avoid running off the runway. A second engine died from fuel exhaustion by the time the plane came to a stop. The flight engineer later measured fuel in the tanks and concluded that less than five minutes total remained.
Following the mission, there was confusion over the identification of the plane. The first eyewitness account by war correspondent William L. Laurence of the New York Times, who accompanied the mission aboard the aircraft piloted by Bock, reported that Sweeney was leading the mission in The Great Artiste. He also noted its "Victor" number as 77, which was that of Bockscar, writing that several personnel commented that 77 was also the jersey number of the football player Red Grange. Laurence had interviewed Sweeney and his crew, and was aware that they referred to their airplane as The Great Artiste. Except for Enola Gay, none of the 393d's B-29s had yet had names painted on the noses, a fact which Laurence himself noted in his account. Unaware of the switch in aircraft, Laurence assumed Victor 77 was The Great Artiste, which was in fact, Victor 89.
Events on the groundAlthough the bomb was more powerful than the one used on Hiroshima, the effect was confined by hillsides to the narrow Urakami Valley. Of 7,500 Japanese employees who worked inside the Mitsubishi Munitions plant, including mobilized students and regular workers, 6,200 were killed. Some 17,000''22,000 others who worked in other war plants and factories in the city died as well. Casualty estimates for immediate deaths vary widely, ranging from 22,000 to 75,000. In the days and months following the explosion, more people died from bomb effects. Because of the presence of undocumented foreign workers, and a number of military personnel in transit, there are great discrepancies in the estimates of total deaths by the end of 1945; a range of 39,000 to 80,000 can be found in various studies.
Unlike Hiroshima's military death toll, only 150 soldiers were killed instantly, including thirty-six from the IJA 134th AAA Regiment of the 4th AAA Division. At least eight known POWs died from the bombing and as many as 13 may have died, including a British citizen, Royal Air Force Corporal Ronald Shaw, and seven Dutch POWs. One American POW, Joe Kieyoomia, was in Nagasaki at the time of the bombing but survived, reportedly having been shielded from the effects of the bomb by the concrete walls of his cell. There were 24 Australian POWs in Nagasaki, all of whom survived.
The radius of total destruction was about 1 mi (1.6 km), followed by fires across the northern portion of the city to 2 mi (3.2 km) south of the bomb. About 58% of the Mitsubishi Arms Plant was damaged, and about 78% of the Mitsubishi Steel Works. The Mitsubishi Electric Works only suffered 10% structural damage as it was on the border of the main destruction zone. The Mitsubishi-Urakami Ordnance Works, the factory that manufactured the type 91 torpedoes released in the attack on Pearl Harbor, was destroyed in the blast.
Plans for more atomic attacks on JapanGroves expected to have another atomic bomb ready for use on August 19, with three more in September and a further three in October. On August 10, he sent a memorandum to Marshall in which he wrote that "the next bomb ... should be ready for delivery on the first suitable weather after 17 or 18 August." On the same day, Marshall endorsed the memo with the comment, "It is not to be released over Japan without express authority from the President."
There was already discussion in the War Department about conserving the bombs then in production for Operation Downfall. "The problem now [August 13] is whether or not, assuming the Japanese do not capitulate, to continue dropping them every time one is made and shipped out there or whether to hold them ... and then pour them all on in a reasonably short time. Not all in one day, but over a short period. And that also takes into consideration the target that we are after. In other words, should we not concentrate on targets that will be of the greatest assistance to an invasion rather than industry, morale, psychology, and the like? Nearer the tactical use rather than other use."
Two more Fat Man assemblies were readied. The third core was scheduled to leave Kirtland Field for Tinian on August 15, and Tibbets was ordered by LeMay to return to Utah to collect it.Robert Bacher was packaging it for shipment in Los Alamos on August 14 when he received word from Groves that the shipment was suspended.
Surrender of Japan and subsequent occupationUntil August 9, Japan's war council still insisted on its four conditions for surrender. On that day Hirohito ordered KÅichi Kido to "quickly control the situation ... because the Soviet Union has declared war against us." He then held an Imperial conference during which he authorized minister Shigenori TÅgÅ to notify the Allies that Japan would accept their terms on one condition, that the declaration "does not comprise any demand which prejudices the prerogatives of His Majesty as a Sovereign ruler."
On August 12, the Emperor informed the imperial family of his decision to surrender. One of his uncles, Prince Asaka, then asked whether the war would be continued if the kokutai could not be preserved. Hirohito simply replied "Of course." As the Allied terms seemed to leave intact the principle of the preservation of the Throne, Hirohito recorded on August 14 his capitulation announcement which was broadcast to the Japanese nation the next day despite a short rebellion by militarists opposed to the surrender.
In his declaration, Hirohito referred to the atomic bombings:
Moreover, the enemy now possesses a new and terrible weapon with the power to destroy many innocent lives and do incalculable damage. Should we continue to fight, not only would it result in an ultimate collapse and obliteration of the Japanese nation, but also it would lead to the total extinction of human civilization.
Such being the case, how are We to save the millions of Our subjects, or to atone Ourselves before the hallowed spirits of Our Imperial Ancestors? This is the reason why We have ordered the acceptance of the provisions of the Joint Declaration of the Powers.
In his "Rescript to the Soldiers and Sailors" delivered on August 17, he stressed the impact of the Soviet invasion and his decision to surrender, omitting any mention of the bombs. Hirohito met with General MacArthur on September 27, saying to him that "[t]he peace party did not prevail until the bombing of Hiroshima created a situation which could be dramatized." Furthermore, the "Rescript to the Soldiers and Sailors" speech he told MacArthur about was just personal, not political, and never stated that the Soviet intervention in Manchuria was the main reason for surrender. In fact, a day after the bombing of Nagasaki and the Soviet invasion of Manchuria, Hirohito ordered his advisers, primarily Chief Cabinet SecretaryHisatsune Sakomizu, Kawada Mizuho, and Masahiro Yasuoka, to write up a surrender speech. In Hirohito's speech, days before announcing it on radio on August 15, he gave three major reasons for surrender: Tokyo's defenses would not be complete before the American invasion of Japan, Ise Shrine would be lost to the Americans, and atomic weapons deployed by the Americans would lead to the death of the entire Japanese race. Despite the Soviet intervention, Hirohito did not mention the Soviets as the main factor for surrender.
Depiction, public response and censorshipLife among the rubble in Hiroshima in March and April 1946. Film footage taken by Lieutenant Daniel A. McGovern (director) and Harry Mimura (cameraman) for a United States Strategic Bombing Survey project.During the war "annihilationist and exterminationalist rhetoric" was tolerated at all levels of U.S. society; according to the British embassy in Washington the Americans regarded the Japanese as "a nameless mass of vermin". Caricatures depicting Japanese as less than human, e.g. monkeys, were common. A 1944 opinion poll that asked what should be done with Japan found that 13% of the U.S. public were in favor of "killing off" all Japanese men, women, and children.
After the Hiroshima bomb detonated successfully, Robert Oppenheimer addressed an assembly at Los Alamos "clasping his hands together like a prize-winning boxer". The Vatican was less enthusiastic; its newspaper L'Osservatore Romano expressed regret that the bomb's inventors did not destroy the weapon for the benefit of humanity. Nonetheless, news of the atomic bombing was greeted enthusiastically in the U.S.; a poll in Fortune magazine in late 1945 showed a significant minority of Americans (22.7%) wishing that more atomic bombs could have been dropped on Japan. The initial positive response was supported by the imagery presented to the public (mainly the powerful images of the mushroom cloud) and the censorship of photographs that showed corpses and maimed survivors.
Wilfred Burchett was the first journalist to visit Hiroshima after the atom bomb was dropped, arriving alone by train from Tokyo on September 2, the day of the formal surrender aboard the USS Missouri. His Morse code dispatch was printed by the Daily Express newspaper in London on September 5, 1945, entitled "The Atomic Plague", the first public report to mention the effects of radiation and nuclear fallout. Burchett's reporting was unpopular with the U.S. military. The U.S. censors suppressed a supporting story submitted by George Weller of the Chicago Daily News, and accused Burchett of being under the sway of Japanese propaganda. Laurence dismissed the reports on radiation sickness as Japanese efforts to undermine American morale, ignoring his own account of Hiroshima's radiation sickness published one week earlier.
The Hiroshima ruins in March and April 1946, by Daniel A. McGovern and Harry MimuraA member of the U.S. Strategic Bombing Survey, Lieutenant Daniel McGovern, used a film crew to document the results in early 1946. The film crew's work resulted in a three-hour documentary entitled The Effects of the Atomic Bombs Against Hiroshima and Nagasaki. The documentary included images from hospitals showing the human effects of the bomb; it showed burned out buildings and cars, and rows of skulls and bones on the ground. It was classified "secret" for the next 22 years. During this time in America, it was a common practice for editors to keep graphic images of death out of films, magazines, and newspapers. The total of 90,000 ft (27,000 m) of film shot by McGovern's cameramen had not been fully aired as of 2009. According to Greg Mitchell, with the 2004 documentary film Original Child Bomb, a small part of that footage managed to reach part of the American public "in the unflinching and powerful form its creators intended".
Motion picture company Nippon Eigasha started sending cameramen to Nagasaki and Hiroshima in September 1945. On October 24, 1945, a U.S. military policeman stopped a Nippon Eigasha cameraman from continuing to film in Nagasaki. All Nippon Eigasha's reels were then confiscated by the American authorities. These reels were in turn requested by the Japanese government, declassified, and saved from oblivion. Some black-and-white motion pictures were released and shown for the first time to Japanese and American audiences in the years from 1968 to 1970. The public release of film footage of the city post attack, and some research about the human effects of the attack, was restricted during the occupation of Japan, and much of this information was censored until the signing of the San Francisco Peace Treaty in 1951, restoring control to the Japanese.
Only the most sensitive and detailed weapons effects information was censored during this period. There was no censorship of the factually written accounts. For example, the book Hiroshima written by Pulitzer Prize winner John Hersey, which was originally published in article form in the popular magazine The New Yorker, on August 31, 1946, is reported to have reached Tokyo in English by January 1947, and the translated version was released in Japan in 1949. The book narrates the stories of the lives of six bomb survivors from immediately prior, to months after, the dropping of the Little Boy bomb.
Post-attack casualtiesFilm footage taken in Hiroshima in March 1946 showing victims with severe burnsIn the spring of 1948, the Atomic Bomb Casualty Commission (ABCC) was established in accordance with a presidential directive from Truman to the National Academy of Sciences '' National Research Council to conduct investigations of the late effects of radiation among the survivors in Hiroshima and Nagasaki. One of the early studies conducted by the ABCC was on the outcome of pregnancies occurring in Hiroshima and Nagasaki, and in a control city, Kure, located 18 mi (29 km) south of Hiroshima, in order to discern the conditions and outcomes related to radiation exposure. Dr. James V. Neel led the study which found that the number of birth defects was not significantly higher among the children of survivors who were pregnant at the time of the bombings. The National Academy of Sciences questioned Neel's procedure which did not filter the Kure population for possible radiation exposure. Among the observed birth defects there was a higher incidence of brain malformation in Nagasaki and Hiroshima, including microencephaly and anencephaly, about 2.75 times the rate seen in Kure.
In 1985, Johns Hopkins University human geneticist James F. Crow examined Neel's research and confirmed that the number of birth defects was not significantly higher in Hiroshima and Nagasaki. Many members of the ABCC and its successor Radiation Effects Research Foundation (RERF) were still looking for possible birth defects or other causes among the survivors decades later, but found no evidence that they were common among the survivors. Despite the insignificance of birth defects found in Neel's study, historian Ronald E. Powaski wrote that Hiroshima experienced "an increase in stillbirths, birth defects, and infant mortality" following the atomic bomb. Neel also studied the longevity of the children who survived the bombings of Hiroshima and Nagasaki, reporting that between 90 and 95 percent were still living 50 years later.
Around 1,900 cancer deaths can be attributed to the after-effects of the bombs. An epidemiology study by the RERF states that from 1950 to 2000, 46% of leukemia deaths and 11% of solid cancer deaths among the bomb survivors were due to radiation from the bombs, the statistical excess being estimated at 200 leukemia and 1,700 solid cancers.
HibakushaPanoramic view of the monument marking the hypocenter, or ground zero, of the atomic bomb explosion over NagasakiThe survivors of the bombings are called hibakusha(èçè
?), a Japanese word that literally translates to "explosion-affected people." As of March 31, 2014[update], 192,719 hibakusha were recognized by the Japanese government, most living in Japan. The government of Japan recognizes about 1% of these as having illnesses caused by radiation. The memorials in Hiroshima and Nagasaki contain lists of the names of the hibakusha who are known to have died since the bombings. Updated annually on the anniversaries of the bombings, as of August 2014[update] the memorials record the names of more than 450,000 hibakusha; 292,325 in Hiroshima and 165,409 in Nagasaki.
Hibakusha and their children were (and still are) victims of severe discrimination in Japan due to public ignorance about the consequences of radiation sickness, with much of the public believing it to be hereditary or even contagious. This is despite the fact that no statistically demonstrable increase of birth defects or congenital malformations was found among the later conceived children born to survivors of Hiroshima and Nagasaki. A study of the long-term psychological effects of the bombings on the survivors found that even 17''20 years after the bombings had occurred survivors showed a higher prevalence of anxiety and somatization symptoms.
Double survivorsOn March 24, 2009, the Japanese government officially recognized Tsutomu Yamaguchi as a double hibakusha. He was confirmed to be 3 km (1.9 mi) from ground zero in Hiroshima on a business trip when Little Boy was detonated. He was seriously burnt on his left side and spent the night in Hiroshima. He arrived at his home city of Nagasaki on August 8, the day before Fat Man was dropped, and he was exposed to residual radiation while searching for his relatives. He was the first officially recognized survivor of both bombings. He died on January 4, 2010, at the age of 93, after a battle with stomach cancer. The 2006 documentary Twice Survived: The Doubly Atomic Bombed of Hiroshima and Nagasaki documented 165 nijÅ hibakusha (lit. double explosion-affected people), and was screened at the United Nations.
Korean survivorsDuring the war, Japan brought as many as 670,000 Korean conscripts to Japan to work as forced labor. About 20,000 Koreans were killed in Hiroshima and another 2,000 died in Nagasaki. Perhaps one in seven of the Hiroshima victims were of Korean ancestry. For many years, Koreans had a difficult time fighting for recognition as atomic bomb victims and were denied health benefits. Most issues have been addressed in recent years through lawsuits.
Debate over bombingsThe atomic bomb was more than a weapon of terrible destruction; it was a psychological weapon.
'-- Henry L. Stimson, 1947The role of the bombings in Japan's surrender and the U.S.'s ethical justification for them has been the subject of scholarly and popular debate for decades. J. Samuel Walker wrote in an April 2005 overview of recent historiography on the issue, "the controversy over the use of the bomb seems certain to continue." He wrote that "The fundamental issue that has divided scholars over a period of nearly four decades is whether the use of the bomb was necessary to achieve victory in the war in the Pacific on terms satisfactory to the United States."
Supporters of the bombings generally assert that they caused the Japanese surrender, preventing casualties on both sides during Operation Downfall. One figure of speech, "One hundred million [subjects of the Japanese Empire] will die for the Emperor and Nation," served as a unifying slogan, although that phrase was intended as a figure of speech along the lines of the "ten thousand years" phrase. In Truman's 1955 Memoirs, "he states that the atomic bomb probably saved half a million U.S. lives'-- anticipated casualties in an Allied invasion of Japan planned for November. Stimson subsequently talked of saving one million U.S. casualties, and Churchill of saving one million American and half that number of British lives." Scholars have pointed out various alternatives that could have ended the war without an invasion, but these alternatives could have resulted in the deaths of many more Japanese. Supporters also point to an order given by the Japanese War Ministry on August 1, 1944, ordering the execution of Allied prisoners of war when the POW camp was in the combat zone.
Those who oppose the bombings cite a number of reasons for their view, among them: a belief that atomic bombing is fundamentally immoral, that the bombings counted as war crimes, that they were militarily unnecessary, that they constituted state terrorism, and that they involved racism against and the dehumanization of the Japanese people. Another popular view among critics of the bombings, originating with Gar Alperovitz in 1965 and becoming the default position in Japanese school history textbooks, is the idea of atomic diplomacy: that the United States used nuclear weapons in order to intimidate the Soviet Union in the early stages of the Cold War. The bombings were part of an already fierce conventional bombing campaign. This, together with the sea blockade and the collapse of Germany (with its implications regarding redeployment), could also have led to a Japanese surrender. At the time United States dropped its atomic bomb on Nagasaki on August 9, 1945, the Soviet Union launched a surprise attack with 1.6 million troops against the Kwantung Army in Manchuria. "The Soviet entry into the war", argued Japanese historian Tsuyoshi Hasegawa, "played a much greater role than the atomic bombs in inducing Japan to surrender because it dashed any hope that Japan could terminate the war through Moscow's mediation".
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Retrieved May 5, 2007. ^Malik 1985 describes how various values were recorded for the B-29's altitude at the moment of bomb release over Hiroshima. The strike report said 30,200 ft, the official history said 31,600 ft, Commander Parson's log entry was 32,700 ft, and the navigator's log was 31,060 ft'--the latter possibly an error transposing two digits. A later calculation using the indicated atmospheric pressure arrived at the figure of 32,200 ft.Similarly, several values have been reported as the altitude of the Little Boy bomb at the moment of detonation. Published sources vary in the range of 1,800 to 2,000 ft (550 to 610 m) above the city. The device was set to explode at 1,885 ft (575 m), but this was approximate. Malik 1985 uses the figure of 1,903 ft (580 m) plus or minus 50 ft (15 m), determined after data review by Hubbell et al 1969. 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The Atomic Bomb: Voices from Hiroshima and Nagasaki. Armonk, New York: M.E. Sharpe. ISBN 0-87332-773-X. OCLC 20057103. Sharp, Patrick B. "From Yellow Peril to Japanese Wasteland: John Hersey's 'Hiroshima'". Twentieth Century Literature46 (2000): 434''452. JSTOR 827841. Sherwin, Martin J. (2003). A World Destroyed: Hiroshima and its Legacies. Stanford, California: Stanford University Press. ISBN 0-8047-3957-9. OCLC 52714712. Sklar, Morty, ed. (1984). Nuke-rebuke: Writers & Artists Against Nuclear Energy & Weapons. Iowa City, Iowa: The Spirit That Moves Us Press. ISBN 0-930370-16-3. OCLC 10072916. SlavinskiÄ, Boris Nikolaevich (2004). The Japanese-Soviet Neutrality Pact: A Diplomatic History, 1941''1945. Nissan Institute/Routledge Japanese Studies Series. London; New York: RoutledgeCurzon. ISBN 978-0-415-32292-8. Sodei, Rinjiro (1998). Were We the Enemy? American Survivors of Hiroshima. Boulder, Colorado: Westview Press. ISBN 0-8133-2960-4. Stohl, Michael (1979). The Politics of Terrorism. New York: M. Dekker. ISBN 978-0-8247-6764-8. OCLC 4495087. Sweeney, Charles; Antonucci, James A.; Antonucci, Marion K. (1997). War's End: An Eyewitness Account of America's Last Atomic Mission. New York: Quill Publishing. ISBN 0-380-78874-8. Thomas, Gordon; Morgan-Witts, Max (1977). Ruin from the Air. London: Hamilton. ISBN 0-241-89726-2. OCLC 252041787. Tibbets, Paul W. (1998). Return Of The Enola Gay. New Hope, Pennsylvania: Enola Gay Remembered. ISBN 0-9703666-0-4. OCLC 69423383. Wainstock, Dennis D. (1996). The Decision to Drop the Atomic Bomb. Westport, Connecticut: Praeger. ISBN 0-275-95475-7. OCLC 33243854. Walker, J. Samuel (January 1990). "The Decision to Use the Bomb: A Historiographical Update". Diplomatic History14 (1): 97''114. doi:10.1111/j.1467-7709.1990.tb00078.x. ISSN 1467-7709. Walker, J. Samuel (April 2005). "Recent Literature on Truman's Atomic Bomb Decision: A Search for Middle Ground". Diplomatic History29 (2): 311''334. doi:10.1111/j.1467-7709.2005.00476.x. ISSN 1467-7709. Retrieved January 30, 2008. Werrell, Kenneth P. (1996). Blankets of Fire: U.S. Bombers over Japan during World War II. Washington, D.C.: Smithsonian Institution Press. ISBN 1-56098-665-4. OCLC 32921746. White, Geoffrey. M. (July 1995). "Memory Wars: The Politics of Remembering the Asia-Pacific War". Asia-Pacific Issues (21). ISSN 1522-0966. Retrieved June 30, 2013. Williams, M. H. (1960). Chronology, 1941''1945. Washington, D.C.: Office of the Chief of Military History, Department of the Army. OCLC 1358166. Zaloga, Steven J.; Noon, Steve (2010). Defense of Japan 1945. Fortress. Oxford: Osprey Publishing. ISBN 1-84603-687-9. OCLC 503042143. Further readingThere is an extensive body of literature concerning the bombings, the decision to use the bombs, and the surrender of Japan. The following sources provide a sampling of prominent works on this subject matter.
Allen, Thomas; Polmar, Norman (1995). Code-Name Downfall. New York: Simon & Schuster. ISBN 0-684-80406-9. The Committee for the Compilation of Materials on Damage Caused by the Atomic Bombs in Hiroshima and Nagasaki (1981). Hiroshima and Nagasaki: The Physical, Medical, and Social Effects of the Atomic Bombings. New York: Basic Books. ISBN 0-465-02985-X. Gosling, Francis George (1994). The Manhattan Project : Making the Atomic Bomb. Washington, D.C.: United States Department of Energy, History Division. OCLC 637052193. Hogan, Michael J. (1996). Hiroshima in History and Memory. Cambridge, New York: Cambridge University Press. ISBN 0-521-56206-6. Kanabun (2012). Kyoko; Tam, Young, eds. A story of a girl who survived an atomic bomb [åçãéã£ãå°å¥"ã®è(C)±]. ASIN B00HJ6H2EK. Retrieved December 25, 2013. Krauss, Robert; Krauss, Amelia (2005). The 509th Remembered: A History of the 509th Composite Group as Told by the Veterans Themselves. Buchanan, Michigan: 509th Press. ISBN 0-923568-66-2. OCLC 59148135. Merton, Thomas (1962). Original Child Bomb: Points for Meditation to be Scratched on the Walls of a Cave. New York: New Directions. OCLC 4527778. Murakami, Chikayasu (2007). Hiroshima no shiroi sora (The White Sky in Hiroshima). Tokyo: Bungeisha. ISBN 4-286-03708-8. Ogura, Toyofumi (1948). Letters from the End of the World: A Firsthand Account of the Bombing of Hiroshima. Tokyo: Kodansha International. ISBN 4-7700-2776-1. Sekimori, Gaynor (1986). Hibakusha: Survivors of Hiroshima and Nagasaki. Tokyo: Kosei Publishing Company. ISBN 4-333-01204-X. Thomas, Gordon; Morgan-Witts, Max (1977). Enola Gay: The Bombing of Hiroshima. New York: Konecky & Konecky. ISBN 1-56852-597-4. Ward, Wilson (Spring 2007). "The Winning Weapon? Rethinking Nuclear Weapons in Light of Hiroshima". International Security31 (4): 162. doi:10.1162/isec.2007.31.4.162. ISSN 1531-4804. Warren, Stafford L. (1966). "Manhattan Project". In Ahnfeldt, Arnold Lorentz. Radiology in World War II. Washington, D.C.: Office of the Surgeon General, Department of the Army. OCLC 630225. External linksArchives"Documents on the Decision to Drop the Atomic Bomb". Harry S. Truman Presidential Library and Museum. Retrieved January 3, 2012. "The Effects of the Atomic Bombings of Hiroshima and Nagasaki". U.S. Strategic Bombing Survey. Harry S. Truman Presidential Library and Museum. 1946. Retrieved January 3, 2012. "President Truman Defends Use of Atomic Bomb, 1945:Original Letters". Shapell Manuscript Foundation. Retrieved February 8, 2014. "Scientific Data of the Nagasaki Atomic Bomb Disaster". Atomic Bomb Disease Institute, Nagasaki University. Retrieved January 3, 2012. "Correspondence Regarding Decision to Drop the Bomb". Nuclear Age Peace Foundation. Retrieved January 3, 2012. "Tale of Two Cities: The Story of Hiroshima and Nagasaki". National Science Digital Library. Retrieved January 3, 2012. "The Atomic Bombings of Hiroshima and Nagasaki". Atomic Archive. 1946. Retrieved January 3, 2012. "The Atomic Bomb and the End of World War II". National Security Archive. Retrieved January 3, 2012. "Nagasaki Archive". Google Earth mapping of Nagasaki bombing archives. Retrieved January 3, 2012. "Hiroshima Archive". Google Earth mapping of Hiroshima bombing archives. Retrieved January 3, 2012. "Annotated bibliography for atomic bombings of Hiroshima and Nagasaki". Alsos Digital Library for Nuclear Issues. Retrieved January 3, 2012. The short film Children of Hiroshima (Reel 1 of 2) (1952) is available for free download at the Internet ArchiveThe short film Children of Hiroshima (Reel 2 of 2) (1952) is available for free download at the Internet Archive"Photo gallery of aftermath pictures". Time-Life. Retrieved February 8, 2014. Video footage of the bombing of Nagasaki (silent) on YouTubeCommemorationMay 8, 1884 '' December 26, 1972
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Manhattan Project - Wikipedia, the free encyclopedia
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The Manhattan Project was a research and development project that produced the first atomic bombs during World War II. It was led by the United States with the support of the United Kingdom and Canada. From 1942 to 1946, the project was under the direction of Major GeneralLeslie Groves of the U.S. Army Corps of Engineers; physicist J. Robert Oppenheimer was the scientific director of the Los Alamos National Laboratory that designed the actual bombs. The Army component of the project was designated the Manhattan District; "Manhattan" gradually superseded the official codename, Development of Substitute Materials, for the entire project. Along the way, the project absorbed its earlier British counterpart, Tube Alloys. The Manhattan Project began modestly in 1939, but grew to employ more than 130,000 people and cost nearly US$2 billion (about $26 billion in 2015 dollars). Over 90% of the cost was for building factories and producing the fissile materials, with less than 10% for development and production of the weapons. Research and production took place at more than 30 sites across the United States, the United Kingdom and Canada.
Two types of atomic bomb were developed during the war. A relatively simple gun-type fission weapon was made using uranium-235, an isotope that makes up only 0.7 percent of natural uranium. Since it is chemically identical to the most common isotope, uranium-238, and has almost the same mass, it proved difficult to separate. Three methods were employed for uranium enrichment: electromagnetic, gaseous and thermal. Most of this work was performed at Oak Ridge, Tennessee. In parallel with the work on uranium was an effort to produce plutonium. Reactors were constructed at Oak Ridge and Hanford, Washington, in which uranium was irradiated and transmuted into plutonium. The plutonium was then chemically separated from the uranium. The gun-type design proved impractical to use with plutonium so a more complex implosion-type weapon was developed in a concerted design and construction effort at the project's principal research and design laboratory in Los Alamos, New Mexico.
The project was also charged with gathering intelligence on the German nuclear energy project. Through Operation Alsos, Manhattan Project personnel served in Europe, sometimes behind enemy lines, where they gathered nuclear materials and documents, and rounded up German scientists. Despite the Manhattan Project's tight security, Soviet atomic spies still penetrated the program.
The first nuclear device ever detonated was an implosion-type bomb at the Trinity test, conducted at New Mexico's Alamogordo Bombing and Gunnery Range on 16 July 1945. Little Boy, a gun-type weapon, and Fat Man, an implosion-type weapon, were used in the atomic bombings of Hiroshima and Nagasaki, respectively. In the immediate postwar years, the Manhattan Project conducted weapons testing at Bikini Atoll as part of Operation Crossroads, developed new weapons, promoted the development of the network of national laboratories, supported medical research into radiology and laid the foundations for the nuclear navy. It maintained control over American atomic weapons research and production until the formation of the United States Atomic Energy Commission in January 1947.
OriginsIn August 1939, prominent physicists Le" Szilrd and Eugene Wigner drafted the Einstein''Szilrd letter, which warned of the potential development of "extremely powerful bombs of a new type". It urged the United States to take steps to acquire stockpiles of uranium ore and accelerate the research of Enrico Fermi and others into nuclear chain reactions. They had it signed by Albert Einstein and delivered to PresidentFranklin D. Roosevelt. Roosevelt called on Lyman Briggs of the National Bureau of Standards to head the Advisory Committee on Uranium to investigate the issues raised by the letter. Briggs held a meeting on 21 October 1939, which was attended by Szilrd, Wigner and Edward Teller. The committee reported back to Roosevelt in November that uranium "would provide a possible source of bombs with a destructiveness vastly greater than anything now known."
Briggs proposed that the National Defense Research Committee (NDRC) spend $167,000 on research into uranium, particularly the uranium-235 isotope, and the recently discovered plutonium. On 28 June 1941, Roosevelt signed Executive Order 8807, which created the Office of Scientific Research and Development (OSRD), with Vannevar Bush as its director. The office was empowered to engage in large engineering projects in addition to research. The NDRC Committee on Uranium became the S-1 Uranium Committee of the OSRD; the word "uranium" was soon dropped for security reasons.
In Britain, Otto Frisch and Rudolf Peierls at the University of Birmingham had made a breakthrough investigating the critical mass of uranium-235 in June 1939. Their calculations indicated that it was within an order of magnitude of 10 kilograms (22 lb), which was small enough to be carried by a bomber of the day. Their March 1940 Frisch''Peierls memorandum initiated the British atomic bomb project and its Maud Committee, which unanimously recommended pursuing the development of an atomic bomb. One of its members, the Australian physicist Mark Oliphant, flew to the United States in late August 1941 and discovered that data provided by the Maud Committee had not reached key American physicists. Oliphant then set out to find out why the committee's findings were apparently being ignored. He met with the Uranium Committee, and visited Berkeley, California, where he spoke persuasively to Ernest O. Lawrence. Lawrence was sufficiently impressed to commence his own research into uranium. He in turn spoke to James B. Conant, Arthur Compton and George Pegram. Oliphant's mission was therefore a success; key American physicists were now aware of the potential power of an atomic bomb.
At a meeting between President Roosevelt, Vannevar Bush, and Vice President Henry A. Wallace on 9 October 1941, the President approved the atomic program. To control it, he created a Top Policy Group consisting of himself'--although he never attended a meeting'--Wallace, Bush, Conant, Secretary of WarHenry L. Stimson, and the Chief of Staff of the Army, GeneralGeorge Marshall. Roosevelt chose the Army to run the project rather than the Navy, as the Army had the most experience with management of large-scale construction projects. He also agreed to coordinate the effort with that of the British, and on 11 October he sent a message to Prime Minister Winston Churchill, suggesting that they correspond on atomic matters.
FeasibilityProposalsThe S-1 Committee held its first meeting on 18 December 1941 "pervaded by an atmosphere of enthusiasm and urgency" in the wake of the attack on Pearl Harbor and the subsequent United States declaration of war upon Japan and then on Germany. Work was proceeding on three different techniques for isotope separation to separate uranium-235 from uranium-238. Lawrence and his team at the University of California, Berkeley, investigated electromagnetic separation, while Eger Murphree and Jesse Wakefield Beams's team looked into gaseous diffusion at Columbia University, and Philip Abelson directed research into thermal diffusion at the Carnegie Institution of Washington and later the Naval Research Laboratory. Murphree was also the head of an unsuccessful separation project using gas centrifuges.
Meanwhile, there were two lines of research into nuclear reactor technology, with Harold Urey continuing research into heavy water at Columbia, while Arthur Compton brought the scientists working under his supervision at Columbia University and Princeton University to the University of Chicago, where he organized the Metallurgical Laboratory in early 1942 to study plutonium and reactors using graphite as a neutron moderator. Briggs, Compton, Lawrence, Murphree, and Urey met on 23 May 1942 to finalize the S-1 Committee recommendations, which called for all five technologies to be pursued. This was approved by Bush, Conant, and Brigadier GeneralWilhelm D. Styer, the chief of staff of Major GeneralBrehon B. Somervell's Services of Supply, who had been designated the Army's representative on nuclear matters. Bush and Conant then took the recommendation to the Top Policy Group with a budget proposal for $54 million for construction by the United States Army Corps of Engineers, $31 million for research and development by OSRD and $5 million for contingencies in fiscal year 1943. The Top Policy Group in turn sent it to the President on 17 June 1942 and he approved it by writing "OK FDR" on the document.
Bomb design conceptsCompton asked the theoretical physicist J. Robert Oppenheimer of the University of California, Berkeley, to take over research into fast neutron calculations'--the key to calculations of critical mass and weapon detonation'--from Gregory Breit, who had quit on 18 May 1942 because of concerns over lax operational security.John H. Manley, a physicist at the Metallurgical Laboratory, was assigned to assist Oppenheimer by contacting and coordinating experimental physics groups scattered across the country. Oppenheimer and Robert Serber of the University of Illinois examined the problems of neutron diffusion'--how neutrons moved in a nuclear chain reaction'--and hydrodynamics'--how the explosion produced by a chain reaction might behave. To review this work and the general theory of fission reactions, Oppenheimer convened meetings at the University of Chicago in June and at the University of California, Berkeley, in July 1942 with theoretical physicists Hans Bethe, John Van Vleck, Edward Teller, Emil Konopinski, Robert Serber, Stan Frankel, and Eldred C. Nelson, the latter three former students of Oppenheimer, and experimental physicistsFelix Bloch, Emilio Segr¨, John Manley, and Edwin McMillan. They tentatively confirmed that a fission bomb was theoretically possible.
There were still many unknown factors. The properties of pure uranium-235 were relatively unknown, as were those of plutonium, an element that had only been discovered in February 1941 by Glenn Seaborg and his team. The scientists at the Berkeley conference envisioned creating plutonium in nuclear reactors where uranium-238 atoms absorbed neutrons that had been emitted from fissioning uranium-235 atoms. At this point no reactor had been built, and only tiny quantities of plutonium were available from cyclotrons. Even by December 1943, only two milligrams had been produced. There were many ways of arranging the fissile material into a critical mass. The simplest was shooting a "cylindrical plug" into a sphere of "active material" with a "tamper"'--dense material that would focus neutrons inward and keep the reacting mass together to increase its efficiency. They also explored designs involving spheroids, a primitive form of "implosion" suggested by Richard C. Tolman, and the possibility of autocatalytic methods, which would increase the efficiency of the bomb as it exploded.
Considering the idea of the fission bomb theoretically settled'--at least until more experimental data was available'--the Berkeley conference then turned in a different direction. Edward Teller pushed for discussion of a more powerful bomb: the "super", now usually referred to as a "hydrogen bomb", which would use the explosive force of a detonating fission bomb to ignite a nuclear fusion reaction in deuterium and tritium. Teller proposed scheme after scheme, but Bethe refused each one. The fusion idea was put aside to concentrate on producing fission bombs. Teller also raised the speculative possibility that an atomic bomb might "ignite" the atmosphere because of a hypothetical fusion reaction of nitrogen nuclei.[note 1] Bethe calculated that it could not happen, and a report co-authored by Teller showed that "no self-propagating chain of nuclear reactions is likely to be started." In Serber's account, Oppenheimer mentioned it to Arthur Compton, who "didn't have enough sense to shut up about it. It somehow got into a document that went to Washington" and was "never laid to rest".[note 2]
OrganizationManhattan DistrictThe Chief of Engineers, Major General Eugene Reybold, selected ColonelJames C. Marshall to head the Army's part of the project in June 1942. Marshall created a liaison office in Washington, D.C., but established his temporary headquarters on the 18th floor of 270 Broadway in New York, where he could draw on administrative support from the Corps of Engineers' North Atlantic Division. It was close to the Manhattan office of Stone & Webster, the principal project contractor, and to Columbia University. He had permission to draw on his former command, the Syracuse District, for staff, and he started with Lieutenant ColonelKenneth Nichols, who became his deputy.
Because most of his task involved construction, Marshall worked in cooperation with the head of the Corps of Engineers Construction Division, Major General Thomas M. Robbins, and his deputy, Colonel Leslie Groves. Reybold, Somervell and Styer decided to call the project "Development of Substitute Materials", but Groves felt that this would draw attention. Since engineer districts normally carried the name of the city where they were located, Marshall and Groves agreed to name the Army's component of the project the Manhattan District. This became official on 13 August, when Reybold issued the order creating the new district. Informally, it was known as the Manhattan Engineer District, or MED. Unlike other districts, it had no geographic boundaries, and Marshall had the authority of a division engineer. Development of Substitute Materials remained as the official codename of the project as a whole, but was supplanted over time by "Manhattan".
Marshall later conceded that, "I had never heard of atomic fission but I did know that you could not build much of a plant, much less four of them for $90 million." A single TNT plant that Nichols had recently built in Pennsylvania had cost $128 million. Nor were they impressed with estimates to the nearest order of magnitude, which Groves compared with telling a caterer to prepare for between ten and a thousand guests. A survey team from Stone & Webster had already scouted a site for the production plants. The War Production Board recommended sites around Knoxville, Tennessee, an isolated area where the Tennessee Valley Authority could supply ample electric power and the rivers could provide cooling water for the reactors. After examining several sites, the survey team selected one near Elza, Tennessee. Conant advised that it be acquired at once and Styer agreed but Marshall temporized, awaiting the results of Conant's reactor experiments before taking action. Of the prospective processes, only Lawrence's electromagnetic separation appeared sufficiently advanced for construction to commence.
Marshall and Nichols began assembling the resources they would need. The first step was to obtain a high priority rating for the project. The top ratings were AA-1 through AA-4 in descending order, although there was also a special AAA rating reserved for emergencies. Ratings AA-1 and AA-2 were for essential weapons and equipment, so Colonel Lucius D. Clay, the deputy chief of staff at Services and Supply for requirements and resources, felt that the highest rating he could assign was AA-3, although he was willing to provide a AAA rating on request for critical materials if the need arose. Nichols and Marshall were disappointed; AA-3 was the same priority as Nichols' TNT plant in Pennsylvania.
Military Policy CommitteeBush became dissatisfied with Colonel Marshall's failure to get the project moving forward expeditiously, specifically the failure to acquire the Tennessee site, the low priority allocated to the project by the Army and the location of his headquarters in New York City. Bush felt that more aggressive leadership was required, and spoke to Harvey Bundy and Generals Marshall, Somervell, and Styer about his concerns. He wanted the project placed under a senior policy committee, with a prestigious officer, preferably Styer, as overall director.
Somervell and Styer selected Groves for the post, informing him on 17 September of this decision, and that General Marshall ordered that he be promoted to brigadier general, as it was felt that the title "general" would hold more sway with the academic scientists working on the Manhattan Project. Groves' orders placed him directly under Somervell rather than Reybold, with Colonel Marshall now answerable to Groves. Groves established his headquarters in Washington, D.C., on the fifth floor of the New War Department Building, where Colonel Marshall had his liaison office. He assumed command of the Manhattan Project on 23 September. Later that day, he attended a meeting called by Stimson, which established a Military Policy Committee, responsible to the Top Policy Group, consisting of Bush (with Conant as an alternate), Styer and Rear AdmiralWilliam R. Purnell. Tolman and Conant were later appointed as Groves' scientific advisers.
On 19 September, Groves went to Donald Nelson, the chairman of the War Production Board, and asked for broad authority to issue a AAA rating whenever it was required. Nelson initially balked but quickly caved in when Groves threatened to go to the President. Groves promised not to use the AAA rating unless it was necessary. It soon transpired that for the routine requirements of the project the AAA rating was too high but the AA-3 rating was too low. After a long campaign, Groves finally received AA-1 authority on 1 July 1944.
One of Groves' early problems was to find a director for Project Y, the group that would design and build the bomb. The obvious choice was one of the three laboratory heads, Urey, Lawrence, or Compton, but they could not be spared. Compton recommended Oppenheimer, who was already intimately familiar with the bomb design concepts. However, Oppenheimer had little administrative experience, and, unlike Urey, Lawrence, and Compton, had not won a Nobel Prize, which many scientists felt that the head of such an important laboratory should have. There were also concerns about Oppenheimer's security status, as many of his associates were Communists, including his brother, Frank Oppenheimer; his wife, Kitty; and his girlfriend, Jean Tatlock. A long conversation on a train in October 1942 convinced Groves and Nichols that Oppenheimer thoroughly understood the issues involved in setting up a laboratory in a remote area and should be appointed as its director. Groves personally waived the security requirements and issued Oppenheimer a clearance on 20 July 1943.
Collaboration with the United KingdomThe British and Americans exchanged nuclear information but did not initially combine their efforts. Britain rebuffed attempts by Bush and Conant in 1941 to strengthen cooperation with its own project, codenamed Tube Alloys, because it was reluctant to share its technological lead and help the United States develop its own atomic bomb. An American scientist who brought a personal letter from Roosevelt to Churchill offering to pay for all research and development in an Anglo-American project was poorly treated, and Churchill did not reply to the letter. The United States as a result decided as early as April 1942 that its offer was rejected, and that it should proceed alone. The United Kingdom did not have the manpower or resources of the United States and despite its early and promising start, Tube Alloys soon fell behind its American counterpart. On 30 July 1942, Sir John Anderson, the minister responsible for Tube Alloys, advised Churchill that: "We must face the fact that ... [our] pioneering work ... is a dwindling asset and that, unless we capitalise it quickly, we shall be outstripped. We now have a real contribution to make to a 'merger.' Soon we shall have little or none." That month Churchill and Roosevelt made an informal, unwritten agreement for atomic collaboration.
The opportunity for an equal partnership no longer existed, however, as shown in August 1942 when the British unsuccessfully demanded substantial control over the project while paying none of the costs. By 1943 the roles of the two countries had reversed from late 1941; in January Conant notified the British that they would no longer receive atomic information except in certain areas. While the British were shocked by the abrogation of the Churchill-Roosevelt agreement, head of the Canadian National Research Council C. J. Mackenzie was less surprised, writing "I can't help feeling that the United Kingdom group [over] emphasizes the importance of their contribution as compared with the Americans." As Conant and Bush told the British, the order came "from the top". The British bargaining position had worsened; the American scientists had decided that the United States no longer needed outside help, and they and others on the bomb policy committee wanted to prevent Britain from being able to build a postwar atomic weapon. The committee supported, and Roosevelt agreed to, restricting the flow of information to what Britain could use during the war'--especially not bomb design'--even if doing so slowed down the American project. By early 1943 the British stopped sending research and scientists to America, and as a result the Americans stopped all information sharing. The British considered ending the supply of Canadian uranium and heavy water to force the Americans to again share, but Canada needed American supplies to produce them. They investigated the possibility of an independent nuclear program, but determined that it could not be ready in time to affect the outcome of the war in Europe.
By March 1943 Conant decided that British help would benefit some areas of the project. James Chadwick and one or two other British scientists were important enough that the bomb design team at Los Alamos needed them, despite the risk of revealing weapon design secrets. In August 1943 Churchill and Roosevelt negotiated the Quebec Agreement, which resulted in a resumption of cooperation between scientists working on the same problem. Britain, however, agreed to restrictions on data on the building of large-scale production plants necessary for the bomb. The subsequent Hyde Park Agreement in September 1944 extended this cooperation to the postwar period. The Quebec Agreement established the Combined Policy Committee to coordinate the efforts of the United States, United Kingdom and Canada. Stimson, Bush and Conant served as the American members of the Combined Policy Committee, Field Marshal Sir John Dill and Colonel J. J. Llewellin were the British members, and C. D. Howe was the Canadian member. Llewellin returned to the United Kingdom at the end of 1943 and was replaced on the committee by Sir Ronald Ian Campbell, who in turn was replaced by the British Ambassador to the United States, Lord Halifax, in early 1945. Sir John Dill died in Washington, D.C., in November 1944 and was replaced both as Chief of the British Joint Staff Mission and as a member of the Combined Policy Committee by Field Marshal Sir Henry Maitland Wilson.
When cooperation resumed after the Quebec agreement, the Americans' progress and expenditures amazed the British. The United States had already spent more than $1 billion ($13,600,000,000 today), while in 1943, the United Kingdom had spent about £0.5 million. Chadwick thus pressed for British involvement in the Manhattan Project to the fullest extent and abandon any hopes of a British project during the war. With Churchill's backing, he attempted to ensure that every request from Groves for assistance was honored. The British Mission that arrived in the United States in December 1943 included Niels Bohr, Otto Frisch, Klaus Fuchs, Rudolf Peierls, and Ernest Titterton. More scientists arrived in early 1944. While those assigned to gaseous diffusion left by the fall of 1944, the 35 working with Lawrence at Berkeley were assigned to existing laboratory groups and stayed until the end of the war. The 19 sent to Los Alamos also joined existing groups, primarily related to implosion and bomb assembly, but not the plutonium-related ones. Part of the Quebec Agreement specified that nuclear weapons would not be used against another country without mutual consent. In June 1945, Wilson agreed that the use of nuclear weapons against Japan would be recorded as a decision of the Combined Policy Committee.
The Combined Policy Committee created the Combined Development Trust in June 1944, with Groves as its chairman, to procure uranium and thorium ores on international markets. The Belgian Congo and Canada held much of the world's uranium outside Eastern Europe, and the Belgian government in exile was in London. Britain agreed to give the United States most of the Belgian ore, as it could not use most of the supply without restricted American research. In 1944, the Trust purchased 3,440,000 pounds (1,560,000 kg) of uranium oxide ore from companies operating mines in the Belgian Congo. In order to avoid briefing US Secretary of the Treasury Henry Morgenthau Jr. on the project, a special account not subject to the usual auditing and controls was used to hold Trust monies. Between 1944 and the time he resigned from the Trust in 1947, Groves deposited a total of $37.5 million into the Trust's account.
Groves appreciated the early British atomic research and the British scientists' contributions to the Manhattan Project, but stated that the United States would have succeeded without them. Whether or not he was correct, the British wartime participation was crucial to the success of the United Kingdom's independent nuclear weapons program after the war when the McMahon Act of 1946 temporarily ended American nuclear cooperation.
Project sitesA selection of US and Canadian sites important to the Manhattan Project. Click on the location for more information.Oak RidgeThe day after he took over the project, Groves took a train to Tennessee with Colonel Marshall to inspect the proposed site there, and Groves was impressed. On 29 September 1942, United States Under Secretary of WarRobert P. Patterson authorized the Corps of Engineers to acquire 56,000 acres (23,000 ha) of land by eminent domain at a cost of $3.5 million. An additional 3,000 acres (1,200 ha) was subsequently acquired. About 1,000 families were affected by the condemnation order, which came into effect on 7 October. Protests, legal appeals, and a 1943 Congressional inquiry were to no avail. By mid-November U.S. Marshals were tacking notices to vacate on farmhouse doors, and construction contractors were moving in. Some families were given two weeks' notice to vacate farms that had been their homes for generations; others had settled there after being evicted to make way for the Great Smoky Mountains National Park in the 1920s or the Norris Dam in the 1930s. The ultimate cost of land acquisition in the area, which was not completed until March 1945, was only about $2.6 million, which worked out to around $47 an acre. When presented with Public Proclamation Number Two, which declared Oak Ridge a total exclusion area that no one could enter without military permission, the Governor of Tennessee, Prentice Cooper, angrily tore it up.
Initially known as the Kingston Demolition Range, the site was officially renamed the Clinton Engineer Works (CEW) in early 1943. While Stone and Webster concentrated on the production facilities, the architectural and engineering firm Skidmore, Owings & Merrill designed and built a residential community for 13,000. The community was located on the slopes of Black Oak Ridge, from which the new town of Oak Ridge got its name. The Army presence at Oak Ridge increased in August 1943 when Nichols replaced Marshall as head of the Manhattan Engineer District. One of his first tasks was to move the district headquarters to Oak Ridge although the name of the district did not change. In September 1943 the administration of community facilities was outsourced to Turner Construction Company through a subsidiary, the Roane-Anderson Company (for Roane and Anderson Counties, in which Oak Ridge was located). Chemical engineers, including William J. Wilcox Jr. and Warren Fuchs, were part of "frantic efforts" to make 10% to 12% enriched uranium 235, known as the code name "tuballoy tetroxide", with tight security and fast approvals for supplies and materials. The population of Oak Ridge soon expanded well beyond the initial plans, and peaked at 75,000 in May 1945, by which time 82,000 people were employed at the Clinton Engineer Works, and 10,000 by Roane-Anderson.
Los AlamosThe idea of locating Project Y at Oak Ridge was considered, but in the end it was decided that it should be in a remote location. On Oppenheimer's recommendation, the search for a suitable site was narrowed to the vicinity of Albuquerque, New Mexico, where Oppenheimer owned a ranch. In October 1942, Major John H. Dudley of the Manhattan Project was sent to survey the area, and he recommended a site near Jemez Springs, New Mexico. On 16 November, Oppenheimer, Groves, Dudley and others toured the site. Oppenheimer feared that the high cliffs surrounding the site would make his people feel claustrophobic, while the engineers were concerned with the possibility of flooding. The party then moved on to the vicinity of the Los Alamos Ranch School. Oppenheimer was impressed and expressed a strong preference for the site, citing its natural beauty and views of the Sangre de Cristo Mountains, which, it was hoped, would inspire those who would work on the project. The engineers were concerned about the poor access road, and whether the water supply would be adequate, but otherwise felt that it was ideal.
Patterson approved the acquisition of the site on 25 November 1942, authorizing $440,000 for the purchase of the site of 54,000 acres (22,000 ha), all but 8,900 acres (3,600 ha) of which were already owned by the Federal Government.Secretary of AgricultureClaude R. Wickard granted use of some 45,100 acres (18,300 ha) of United States Forest Service land to the War Department "for so long as the military necessity continues". The need for land for a new road, and later for a right of way for a 25-mile (40 km) power line, eventually brought wartime land purchases to 45,737 acres (18,509.1 ha), but only $414,971 was spent. Construction was contracted to the M. M. Sundt Company of Tucson, Arizona, with Willard C. Kruger and Associates of Santa Fe, New Mexico, as architect and engineer. Work commenced in December 1942. Groves initially allocated $300,000 for construction, three times Oppenheimer's estimate, with a planned completion date of 15 March 1943. It soon became clear that the scope of Project Y was greater than expected, and by the time Sundt finished in 30 November 1943, over $7 million had been spent.
Because it was secret, Los Alamos was referred to as "Site Y" or "the Hill". Birth certificates of babies born in Los Alamos during the war listed their place of birth as PO Box 1663 in Santa Fe. Initially Los Alamos was to have been a military laboratory with Oppenheimer and other researchers commissioned into the Army. Oppenheimer went so far as to order himself a lieutenant colonel's uniform, but two key physicists, Robert Bacher and Isidor Rabi, balked at the idea. Conant, Groves and Oppenheimer then devised a compromise whereby the laboratory was operated by the University of California under contract to the War Department.
ArgonneAn Army-OSRD council on 25 June 1942 decided to build a pilot plant for plutonium production in Red Gate Woods southwest of Chicago. In July, Nichols arranged for a lease of 1,025 acres (415 ha) from the Cook County Forest Preserve District, and Captain James F. Grafton was appointed Chicago area engineer. It soon became apparent that the scale of operations was too great for the area, and it was decided to build the plant at Oak Ridge, and keep a research and testing facility in Chicago.
Delays in establishing the plant in Red Gate Woods led Compton to authorize the Metallurgical Laboratory to construct the first nuclear reactor beneath the bleachers of Stagg Field at the University of Chicago. The reactor required an enormous amount of graphite blocks and uranium pellets. At the time, there was a limited source of pure uranium. Frank Spedding of Iowa State University were able to produce only two short tons of pure uranium. Additional three short tons of uranium metal was supplied by Westinghouse Lamp Plant which was produced in a rush with makeshift process. A large square balloon was constructed by Goodyear Tire to encase the reactor. On 2 December 1942, a team led by Enrico Fermi initiated the first artificial[note 3] self-sustaining nuclear chain reaction in an experimental reactor known as Chicago Pile-1. The point at which a reaction becomes self-sustaining became known as "going critical". Compton reported the success to Conant in Washington, D.C., by a coded phone call, saying, "The Italian navigator [Fermi] has just landed in the new world."[note 4]
In January 1943, Grafton's successor, Major Arthur V. Peterson, ordered Chicago Pile-1 dismantled and reassembled at Red Gate Woods, as he regarded the operation of a reactor as too hazardous for a densely populated area. After the war, the operations that remained at Red Gate moved to the new Argonne National Laboratory about 6 miles (9.7 km) away.
HanfordBy December 1942 there were concerns that even Oak Ridge was too close to a major population center (Knoxville) in the unlikely event of a major nuclear accident. Groves recruited DuPont in November 1942 to be the prime contractor for the construction of the plutonium production complex. DuPont was offered a standard cost plus fixed fee contract, but the President of the company, Walter S. Carpenter, Jr., wanted no profit of any kind, and asked for the proposed contract to be amended to explicitly exclude the company from acquiring any patent rights. This was accepted, but for legal reasons a nominal fee of one dollar was agreed upon. After the war, DuPont asked to be released from the contract early, and had to return 33 cents.
DuPont recommended that the site be located far from the existing uranium production facility at Oak Ridge. In December 1942, Groves dispatched Colonel Franklin Matthias and DuPont engineers to scout potential sites. Matthias reported that Hanford Site near Richland, Washington, was "ideal in virtually all respects". It was isolated and near the Columbia River, which could supply sufficient water to cool the reactors that would produce the plutonium. Groves visited the site in January and established the Hanford Engineer Works (HEW), codenamed "Site W".
Under Secretary Patterson gave his approval on 9 February, allocating $5 million for the acquisition of 40,000 acres (16,000 ha) of land in the area. The federal government relocated some 1,500 residents of White Bluffs and Hanford, and nearby settlements, as well as the Wanapum and other tribes using the area. A dispute arose with farmers over compensation for crops, which had already been planted before the land was acquired. Where schedules allowed, the Army allowed the crops to be harvested, but this was not always possible. The land acquisition process dragged on and was not completed before the end of the Manhattan Project in December 1946.
The dispute did not delay work. Although progress on the reactor design at Metallurgical Laboratory and DuPont was not sufficiently advanced to accurately predict the scope of the project, a start was made in April 1943 on facilities for an estimated 25,000 workers, half of whom were expected to live on-site. By July 1944, some 1,200 buildings had been erected and nearly 51,000 people were living in the construction camp. As area engineer, Matthias exercised overall control of the site. At its peak, the construction camp was the third most populous town in Washington state. Hanford operated a fleet of over 900 buses, more than the city of Chicago. Like Los Alamos and Oak Ridge, Richland was a gated community with restricted access, but it looked more like a typical wartime American boomtown: the military profile was lower, and physical security elements like high fences, towers and guard dogs were less evident.
Canadian sitesBritish ColumbiaCominco had produced electrolytic hydrogen at Trail, British Columbia, since 1930. Urey suggested in 1941 that it could produce heavy water. To the existing $10 million plant consisting of 3,215 cells consuming 75 MW of hydroelectric power, secondary electrolysis cells were added to increase the deuterium concentration in the water from 2.3% to 99.8%. For this process, Hugh Taylor of Princeton developed a platinum-on-carbon catalyst for the first three stages while Urey developed a nickel-chromia one for the fourth stage tower. The final cost was $2.8 million. The Canadian Government did not officially learn of the project until August 1942. Trail's heavy water production started in January 1944 and continued until 1956. Heavy water from Trail was used for Chicago Pile 3, the first reactor using heavy water and natural uranium, which went critical on 15 May 1944.
OntarioThe Chalk River, Ontario, site was established to rehouse the Allied effort at the Montreal Laboratory away from an urban area. A new community was built at Deep River, Ontario, to provide residences and facilities for the team members. The site was chosen for its proximity to the industrial manufacturing area of Ontario and Quebec, and proximity to a rail head adjacent to a large military base, Camp Petawawa. Located on the Ottawa River, it had access to abundant water. The first director of the new laboratory was John Cockcroft, later replaced by Bennett Lewis. A pilot reactor known as ZEEP (zero-energy experimental pile) became the first Canadian reactor, and the first to be completed outside the United States, when it went critical in September 1945. A larger 10 MW NRX reactor, which was designed during the war, was completed and went critical in July 1947.
Northwest TerritoriesThe Eldorado Mine at Port Radium was a source of uranium ore for the project.
Heavy water sitesMain article: P-9 ProjectAlthough DuPont's preferred designs for the nuclear reactors were helium cooled and used graphite as a moderator, DuPont still expressed an interest in using heavy water as a backup, in case the graphite reactor design proved infeasible for some reason. For this purpose, it was estimated that 3 long tons (3.0 t) of heavy water would be required per month. The P-9 Project was the government's code name for the heavy water production program. As the plant at Trail, which was then under construction, could produce 0.5 long tons (0.51 t) per month, additional capacity was required. Groves therefore authorized DuPont to establish heavy water facilities at the Morgantown Ordnance Works, near Morgantown, West Virginia; at the Wabash River Ordnance Works, near Dana and Newport, Indiana; and at the Alabama Ordnance Works, near Childersburg and Sylacauga, Alabama. Although known as Ordnance Works and paid for under Ordnance Department contracts, they were built and operated by the Army Corps of Engineers. The American plants used a process different from Trail's; heavy water was extracted by distillation, taking advantage of the slightly higher boiling point of heavy water.
UraniumOreThe key raw material for the project was uranium, which was used as fuel for the reactors, as feed that was transformed into plutonium, and, in its enriched form, in the atomic bomb itself. There were four known major deposits of uranium in 1940: in Colorado, in northern Canada, in Joachimstal in Czechoslovakia, and in the Belgian Congo. All but Joachimstal were in allied hands. A November 1942 survey determined that sufficient quantities of uranium were available to satisfy the project's requirements. Nichols arranged with the State Department for export controls to be placed on uranium oxide and negotiated for the purchase of 1,200 long tons (1,200 t) of uranium ore from the Belgian Congo that was being stored in a warehouse on Staten Island and the remaining stocks of mined ore stored in the Congo. He negotiated with Eldorado Gold Mines for the purchase of ore from its refinery in Port Hope, Ontario, and its shipment in 100-ton lots. The Canadian government subsequently bought up the company's stock until it acquired a controlling interest.
While these purchases assured a sufficient supply to meet wartime needs, the American and British leaders concluded that it was in their countries' interest to gain control of as much of the world's uranium deposits as possible. The richest source of ore was the Shinkolobwe mine in the Belgian Congo, but it was flooded and closed. Nichols unsuccessfully attempted to negotiate its reopening and the sale of the entire future output to the United States with Edgar Sengier, the director of the company that owned the mine, Union Mini¨re du Haut Katanga. The matter was then taken up by the Combined Policy Committee. As 30 percent of Union Mini¨re's stock was controlled by British interests, the British took the lead in negotiations. Sir John Anderson and Ambassador John Winant hammered out a deal with Sengier and the Belgian government in May 1944 for the mine to be reopened and 1,720 long tons (1,750 t) of ore to be purchased at $1.45 a pound. To avoid dependence on the British and Canadians for ore, Groves also arranged for the purchase of US Vanadium Corporation's stockpile in Uravan, Colorado. Uranium mining in Colorado yielded about 800 long tons (810 t) of ore.
Mallinckrodt Incorporated in St. Louis, Missouri, took the raw ore and dissolved it in nitric acid to produce uranyl nitrate. Ether was then added in a liquid''liquid extraction process to separate the impurities from the uranyl nitrate. This was then heated to form uranium trioxide, which was reduced to highly pure uranium dioxide. By July 1942, Mallinckrodt was producing a ton of highly pure oxide a day, but turning this into uranium metal initially proved more difficult for contractors Westinghouse and Metal Hydrides. Production was too slow and quality was unacceptably low. A special branch of the Metallurgical Laboratory was established at Iowa State College in Ames, Iowa, under Frank Spedding to investigate alternatives, and its Ames process became available in 1943.
Isotope separationNatural uranium consists of 99.3% uranium-238 and 0.7% uranium-235, but only the latter is fissile. The chemically identical uranium-235 has to be physically separated from the more plentiful isotope. Various methods were considered for uranium enrichment, most of which was carried out at Oak Ridge.
The most obvious technology, the centrifuge, failed, but electromagnetic separation, gaseous diffusion, and thermal diffusion technologies were all successful and contributed to the project. In February 1943, Groves came up with the idea of using the output of some plants as the input for others.
CentrifugesThe centrifuge process was regarded as the only promising separation method in April 1942.Jesse Beams had developed such a process at the University of Virginia during the 1930s, but had encountered technical difficulties. The process required high rotational speeds, but at certain speeds harmonic vibrations developed that threatened to tear the machinery apart. It was therefore necessary to accelerate quickly through these speeds. In 1941 he began working with uranium hexafluoride, the only known gaseous compound of uranium, and was able to separate uranium-235. At Columbia, Urey had Cohen investigate the process, and he produced a body of mathematical theory making it possible to design a centrifugal separation unit, which Westinghouse undertook to construct.
Scaling this up to a production plant presented a formidable technical challenge. Urey and Cohen estimated that producing a kilogram (2.2 lb) of uranium-235 per day would require up to 50,000 centrifuges with 1-meter (3 ft 3 in) rotors, or 10,000 centrifuges with 4-meter (13 ft) rotors, assuming that 4-meter rotors could be built. The prospect of keeping so many rotors operating continuously at high speed appeared daunting, and when Beams ran his experimental apparatus, he obtained only 60% of the predicted yield, indicating that more centrifuges would be required. Beams, Urey and Cohen then began work on a series of improvements which promised to increase the efficiency of the process. However, frequent failures of motors, shafts and bearings at high speeds delayed work on the pilot plant. In November 1942 the centrifuge process was abandoned by the Military Policy Committee following a recommendation by Conant, Nichols and August C. Klein of Stone & Webster.
Electromagnetic separationElectromagnetic isotope separation was developed by Lawrence at the University of California Radiation Laboratory. This method employed devices known as calutrons, a hybrid of the standard laboratory mass spectrometer and cyclotron. The name was derived from the words "California", "university" and "cyclotron". In the electromagnetic process, a magnetic field deflected charged particles according to mass. The process was neither scientifically elegant nor industrially efficient. Compared with a gaseous diffusion plant or a nuclear reactor, an electromagnetic separation plant would consume more scarce materials, require more manpower to operate, and cost more to build. Nonetheless, the process was approved because it was based on proven technology and therefore represented less risk. Moreover, it could be built in stages, and rapidly reach industrial capacity.
Marshall and Nichols discovered that the electromagnetic isotope separation process would require 5,000 tons of copper, which was in desperately short supply. However, silver could be substituted, in an 11:10 ratio. On 3 August 1942, Nichols met with Under Secretary of the TreasuryDaniel W. Bell and asked for the transfer of 6,000 tons of silver bullion from the West Point Depository. "Young man," Bell told him, "you may think of silver in tons but the Treasury will always think of silver in troy ounces!" Eventually, 14,700 tons were used.
The 1,000-troy-ounce (31 kg) silver bars were cast into cylindrical billets and taken to Phelps Dodge in Bayway, New Jersey, where they were extruded into strips 0.625 inches (15.9 mm) thick, 3 inches (76 mm) wide and 40 feet (12 m) long. These were wound onto magnetic coils by Allis-Chalmers in Milwaukee, Wisconsin. After the war, all the machinery was dismantled and cleaned and the floorboards beneath the machinery were ripped up and burned to recover minute amounts of silver. In the end, only 1/3,600,000th was lost. The last silver was returned in May 1970.
Responsibility for the design and construction of the electromagnetic separation plant, which came to be called Y-12, was assigned to Stone & Webster by the S-1 Committee in June 1942. The design called for five first-stage processing units, known as Alpha racetracks, and two units for final processing, known as Beta racetracks. In September 1943 Groves authorized construction of four more racetracks, known as Alpha II. Construction began in February 1943.
When the plant was started up for testing on schedule in October, the 14-ton vacuum tanks crept out of alignment because of the power of the magnets, and had to be fastened more securely. A more serious problem arose when the magnetic coils started shorting out. In December Groves ordered a magnet to be broken open, and handfuls of rust were found inside. Groves then ordered the racetracks to be torn down and the magnets sent back to the factory to be cleaned. A pickling plant was established on-site to clean the pipes and fittings. The second Alpha I was not operational until the end of January 1944, the first Beta and first and third Alpha I's came online in March, and the fourth Alpha I was operational in April. The four Alpha II racetracks were completed between July and October 1944.
Tennessee Eastman was hired to manage Y-12 on the usual cost plus fixed fee basis, with a fee of $22,500 per month plus $7,500 per racetrack for the first seven racetracks and $4,000 per additional racetrack. The calutrons were initially operated by scientists from Berkeley to remove bugs and achieve a reasonable operating rate. They were then turned over to trained Tennessee Eastman operators who had only a high school education. Nichols compared unit production data, and pointed out to Lawrence that the young "hillbilly" girl operators were outperforming his PhDs. They agreed to a production race and Lawrence lost, a morale boost for the Tennessee Eastman workers and supervisors. The girls were "trained like soldiers not to reason why", while "the scientists could not refrain from time-consuming investigation of the cause of even minor fluctuations of the dials."
Y-12 initially enriched the uranium-235 content to between 13% and 15%, and shipped the first few hundred grams of this to Los Alamos in March 1944. Only 1 part in 5,825 of the uranium feed emerged as final product. Much of the rest was splattered over equipment in the process. Strenuous recovery efforts helped raise production to 10% of the uranium-235 feed by January 1945. In February the Alpha racetracks began receiving slightly enriched (1.4%) feed from the new S-50 thermal diffusion plant. The next month it received enhanced (5%) feed from the K-25 gaseous diffusion plant. By April K-25 was producing uranium sufficiently enriched to feed directly into the Beta tracks.
Gaseous diffusionThe most promising but also the most challenging method of isotope separation was gaseous diffusion. Graham's law states that the rate of effusion of a gas is inversely proportional to the square root of its molecular mass, so in a box containing a semi-permeable membrane and a mixture of two gases, the lighter molecules will pass out of the container more rapidly than the heavier molecules. The gas leaving the container is somewhat enriched in the lighter molecules, while the residual gas is somewhat depleted. The idea was that such boxes could be formed into a cascade of pumps and membranes, with each successive stage containing a slightly more enriched mixture. Research into the process was carried out at Columbia University by a group that included Harold Urey, Karl P. Cohen and John R. Dunning.
In November 1942 the Military Policy Committee approved the construction of a 600-stage gaseous diffusion plant. On 14 December, M. W. Kellogg accepted an offer to construct the plant, which was codenamed K-25. A cost plus fixed fee contract was negotiated, eventually totaling $2.5 million. A separate corporate entity called Kellex was created for the project, headed by Percival C. Keith, one of Kellogg's vice presidents. The process faced formidable technical difficulties. The highly corrosive gas uranium hexafluoride would have to be used, as no substitute could be found, and the motors and pumps would have to be vacuum tight and enclosed in inert gas. The biggest problem was the design of the barrier, which would have to be strong, porous and resistant to corrosion by uranium hexafluoride. The best choice for this seemed to be nickel. Edward Adler and Edward Norris created a mesh barrier from electroplated nickel. A six-stage pilot plant was built at Columbia to test the process, but the Norris-Adler prototype proved to be too brittle. A rival barrier was developed from powdered nickel by Kellex, the Bell Telephone Laboratories and the Bakelite Corporation. In January 1944, Groves ordered the Kellex barrier into production.
Kellex's design for K-25 called for a four-story 0.5-mile (0.80 km) long U-shaped structure containing 54 contiguous buildings. These were divided into nine sections. Within these were cells of six stages. The cells could be operated independently, or consecutively within a section. Similarly, the sections could be operated separately or as part of a single cascade. A survey party began construction by marking out the 500-acre (2.0 km2) site in May 1943. Work on the main building began in October 1943, and the six-stage pilot plant was ready for operation on 17 April 1944. In 1945 Groves canceled the upper stages of the plant, directing Kellex to instead design and build a 540-stage side feed unit, which became known as K-27. Kellex transferred the last unit to the operating contractor, Union Carbide and Carbon, on 11 September 1945. The total cost, including the K-27 plant completed after the war, came to $480 million.
The production plant commenced operation in February 1945, and as cascade after cascade came online, the quality of the product increased. By April 1945, K-25 had attained a 1.1% enrichment and the output of the S-50 thermal diffusion plant began being used as feed. Some product produced the next month reached nearly 7% enrichment. In August, the last of the 2,892 stages commenced operation. K-25 and K-27 achieved their full potential in the early postwar period, when they eclipsed the other production plants and became the prototypes for a new generation of plants.
Thermal diffusionThe thermal diffusion process was based on Sydney Chapman and David Enskog's theory, which explained that when a mixed gas passes through a temperature gradient, the heavier one tends to concentrate at the cold end and the lighter one at the warm end. Since hot gases tend to rise and cool ones tend to fall, this can be used as a means of isotope separation. This process was first demonstrated by H. Clusius and G. Dickel in Germany in 1938. It was developed by US Navy scientists, but was not one of the enrichment technologies initially selected for use in the Manhattan Project. This was primarily due to doubts about its technical feasibility, but the inter-service rivalry between the Army and Navy also played a part.
The Naval Research Laboratory continued the research under Philip Abelson's direction, but there was little contact with the Manhattan Project until April 1944, when Captain William S. Parsons, the naval officer who was in charge of ordnance development at Los Alamos, brought Oppenheimer news of encouraging progress in the Navy's experiments on thermal diffusion. Oppenheimer wrote to Groves suggesting that the output of a thermal diffusion plant could be fed into Y-12. Groves set up a committee consisting of Warren K. Lewis, Eger Murphree and Richard Tolman to investigate the idea, and they estimated that a thermal diffusion plant costing $3.5 million could enrich 50 kilograms (110 lb) of uranium per week to nearly 0.9% uranium-235. Groves approved its construction on 24 June 1944.
Groves contracted with the H. K. Ferguson Company of Cleveland, Ohio, to build the thermal diffusion plant, which was designated S-50. Groves' advisers, Karl Cohen and W. I. Thompson from Standard Oil, estimated that it would take six months to build. Groves gave Ferguson just four. Plans called for the installation of 2,142 48-foot-tall (15 m) diffusion columns arranged in 21 racks. Inside each column were three concentric tubes. Steam, obtained from the nearby K-25 powerhouse at a pressure of 100 pounds per square inch (690 kPa) and temperature of 545 °F (285 °C), flowed downward through the innermost 1.25-inch (32 mm) nickel pipe, while water at 155 °F (68 °C) flowed upward through the outermost iron pipe. Isotope separation occurred in the uranium hexafluoride gas between the nickel and copper pipes.
Work commenced on 9 July 1944, and S-50 began partial operation in September. Ferguson operated the plant through a subsidiary known as Fercleve. The plant produced just 10.5 pounds (4.8 kg) of 0.852% uranium-235 in October. Leaks limited production and forced shutdowns over the next few months, but in June 1945 it produced 12,730 pounds (5,770 kg). By March 1945, all 21 production racks were operating. Initially the output of S-50 was fed into Y-12, but starting in March 1945 all three enrichment processes were run in series. S-50 became the first stage, enriching from 0.71% to 0.89%. This material was fed into the gaseous diffusion process in the K-25 plant, which produced a product enriched to about 23%. This was, in turn, fed into Y-12, which boosted it to about 89%, sufficient for nuclear weapons.
Aggregate U-235 productionAbout 50 kilograms (110 lb) of uranium enriched to 89% uranium-235 was delivered to Los Alamos by July 1945. The entire 50 kg, along with some 50%-enriched, averaging out to about 85% enriched, were used in Little Boy
PlutoniumThe second line of development pursued by the Manhattan Project used the fissile element plutonium. Although small amounts of plutonium exist in nature, the best way to obtain large quantities of the element is in a nuclear reactor, in which natural uranium is bombarded by neutrons. The uranium-238 is transmuted into uranium-239, which rapidly decays, first into neptunium-239 and then into plutonium-239. Only a small amount of the uranium-238 will be transformed, so the plutonium must be chemically separated from the remaining uranium, from any initial impurities, and from fission products.
X-10 Graphite ReactorIn March 1943, DuPont began construction of a plutonium plant on a 112-acre (0.5 km2) site at Oak Ridge. Intended as a pilot plant for the larger production facilities at Hanford, it included the air-cooled X-10 Graphite Reactor, a chemical separation plant, and support facilities. Because of the subsequent decision to construct water-cooled reactors at Hanford, only the chemical separation plant operated as a true pilot. The X-10 Graphite Reactor consisted of a huge block of graphite, 24 feet (7.3 m) long on each side, weighing around 1,500 long tons (1,500 t), surrounded by 7 feet (2.1 m) of high-density concrete as a radiation shield.
The greatest difficulty was encountered with the uranium slugs produced by Mallinckrodt and Metal Hydrides. These somehow had to be coated in aluminum to avoid corrosion and the escape of fission products into the cooling system. The Grasselli Chemical Company attempted to develop a hot dipping process without success. Meanwhile Alcoa tried canning. A new process for flux-less welding was developed, and 97% of the cans passed a standard vacuum test, but high temperature tests indicated a failure rate of more than 50%. Nonetheless, production began in June 1943. The Metallurgical Laboratory eventually developed an improved welding technique with the help of General Electric, which was incorporated into the production process in October 1943.
Watched by Fermi and Compton, the X-10 Graphite Reactor went critical on 4 November 1943 with about 30 long tons (30 t) of uranium. A week later the load was increased to 36 long tons (37 t), raising its power generation to 500 kW, and by the end of the month the first 500 milligrams (0.018 oz) of plutonium was created. Modifications over time raised the power to 4,000 kW in July 1944. X-10 operated as a production plant until January 1945, when it was turned over to research activities.
Hanford reactorsAlthough an air-cooled design was chosen for the reactor at Oak Ridge to facilitate rapid construction, it was recognized that this would be impractical for the much larger production reactors. Initial designs by the Metallurgical Laboratory and DuPont used helium for cooling, before they determined that a water-cooled reactor would be simpler, cheaper and quicker to build. The design did not become available until 4 October 1943; in the meantime, Matthias concentrated on improving the Hanford site by erecting accommodations, improving the roads, building a railway switch line, and upgrading the electricity, water and telephone lines.
As at Oak Ridge, the most difficulty was encountered while canning the uranium slugs, which commenced at Hanford in March 1944. They were pickled to remove dirt and impurities, dipped in molten bronze, tin, and aluminum-silicon alloy, canned using hydraulic presses, and then capped using arc welding under an argon atmosphere. Finally, they were subjected to a series of tests to detect holes or faulty welds. Disappointingly, most canned slugs initially failed the tests, resulting in an output of only a handful of canned slugs per day. But steady progress was made and by June 1944 production increased to the point where it appeared that enough canned slugs would be available to start Reactor B on schedule in August 1944.
Work began on Reactor B, the first of six planned 250 MW reactors, on 10 October 1943. The reactor complexes were given letter designations A through F, with B, D and F sites chosen to be developed first, as this maximised the distance between the reactors. They would be the only ones constructed during the Manhattan Project. Some 390 long tons (400 t) of steel, 17,400 cubic yards (13,300 m3) of concrete, 50,000 concrete blocks and 71,000 concrete bricks were used to construct the 120-foot (37 m) high building.
Construction of the reactor itself commenced in February 1944. Watched by Compton, Matthias, DuPont's Crawford Greenewalt, Leona Woods and Fermi, who inserted the first slug, the reactor was powered up beginning on 13 September 1944. Over the next few days, 838 tubes were loaded and the reactor went critical. Shortly after midnight on 27 September, the operators began to withdraw the control rods to initiate production. At first all appeared well but around 03:00 the power level started to drop and by 06:30 the reactor had shut down completely. The cooling water was investigated to see if there was a leak or contamination. The next day the reactor started up again, only to shut down once more.
Fermi contacted Chien-Shiung Wu, who identified the cause of the problem as neutron poisoning from xenon-135, which has a half-life of 9.2 hours. Fermi, Woods, Donald J. Hughes and John Archibald Wheeler then calculated the nuclear cross section of xenon-135, which turned out to be 30,000 times that of uranium. Fortunately, DuPont engineer George Graves had deviated from the Metallurgical Laboratory's original design in which the reactor had 1,500 tubes arranged in a circle, and had added an additional 504 tubes to fill in the corners. The scientists had originally considered this overengineering a waste of time and money, but Fermi realized that by loading all 2,004 tubes, the reactor could reach the required power level and efficiently produce plutonium. Reactor D was started on 17 December 1944 and Reactor F on 25 February 1945.
Separation processMeanwhile, the chemists considered the problem of how plutonium could be separated from uranium when its chemical properties were not known. Working with the minute quantities of plutonium available at the Metallurgical Laboratory in 1942, a team under Charles M. Cooper developed a lanthanum fluoride process for separating uranium and plutonium, which was chosen for the pilot separation plant. A second separation process, the bismuth phosphate process, was subsequently developed by Seaborg and Stanly G. Thomson. This process worked by toggling plutonium between its +4 and +6 oxidation states in solutions of bismuth phosphate. In the former state, the plutonium was precipitated; in the latter, it stayed in solution and the other products were precipitated.
Greenewalt favored the bismuth phosphate process due to the corrosive nature of lanthanum fluoride, and it was selected for the Hanford separation plants. Once X-10 began producing plutonium, the pilot separation plant was put to the test. The first batch was processed at 40% efficiency but over the next few months this was raised to 90%.
At Hanford, top priority was initially given to the installations in the 300 area. This contained buildings for testing materials, preparing uranium, and assembling and calibrating instrumentation. One of the buildings housed the canning equipment for the uranium slugs, while another contained a small test reactor. Notwithstanding the high priority allocated to it, work on the 300 area fell behind schedule due to the unique and complex nature of the 300 area facilities, and wartime shortages of labor and materials.
Early plans called for the construction of two separation plants in each of the areas known as 200-West and 200-East. This was subsequently reduced to two, the T and U plants, in 200-West and one, the B plant, at 200-East. Each separation plant consisted of four buildings: a process cell building or "canyon" (known as 221), a concentration building (224), a purification building (231) and a magazine store (213). The canyons were each 800 feet (240 m) long and 65 feet (20 m) wide. Each consisted of forty 17.7-by-13-by-20-foot (5.4 by 4.0 by 6.1 m) cells.
Work began on 221-T and 221-U in January 1944, with the former completed in September and the latter in December. The 221-B building followed in March 1945. Because of the high levels of radioactivity involved, all work in the separation plants had to be conducted by remote control using closed-circuit television, something unheard of in 1943. Maintenance was carried out with the aid of an overhead crane and specially designed tools. The 224 buildings were smaller because they had less material to process, and it was less radioactive. The 224-T and 224-U buildings were completed on 8 October 1944, and 224-B followed on 10 February 1945. The purification methods that were eventually used in 231-W were still unknown when construction commenced on 8 April 1944, but the plant was complete and the methods were selected by the end of the year. On 5 February 1945, Matthias hand-delivered the first shipment of 80 grams (2.6 ozt) of 95%-pure plutonium nitrate to a Los Alamos courier in Los Angeles.
Weapon designIn 1943, development efforts were directed to a gun-type fission weapon with plutonium called Thin Man. Initial research on the properties of plutonium was done using cyclotron-generated plutonium-239, which was extremely pure, but could only be created in very small amounts. Los Alamos received the first sample of plutonium from the Clinton X-10 reactor in April 1944 and within days Emilio Segr¨ discovered a problem: the reactor-bred plutonium had a higher concentration of plutonium-240, resulting in up to five times the spontaneous fission rate of cyclotron plutonium. Seaborg had correctly predicted in March 1943 that some of the plutonium-239 would absorb a neutron and become plutonium-240.
This made reactor plutonium unsuitable for use in a gun-type weapon. The plutonium-240 would start the chain reaction too quickly, causing a predetonation that would release enough energy to disperse the critical mass with a minimal amount of plutonium reacted (a fizzle). A faster gun was suggested but found to be impractical. The possibility of separating the isotopes was considered and rejected, as plutonium-240 is even harder to separate from plutonium-239 than uranium-235 from uranium-238.
Work on an alternative method of bomb design, known as implosion, had begun earlier at the instigation of the physicist Seth Neddermeyer. Implosion used explosives to crush a subcritical sphere of fissile material into a smaller and denser form. When the fissile atoms are packed closer together, the rate of neutron capture increases, and the mass becomes a critical mass. The metal needs to travel only a very short distance, so the critical mass is assembled in much less time than it would take with the gun method. Neddermeyer's 1943 and early 1944 investigations into implosion showed promise, but also made it clear that the problem would be much more difficult from a theoretical and engineering perspective than the gun design. In September 1943, John von Neumann, who had experience with shaped charges used in armor-piercing shells, argued that not only would implosion reduce the danger of predetonation and fizzle, but would make more efficient use of the fissionable material. He proposed using a spherical configuration instead of the cylindrical one that Neddermeyer was working on.
By July 1944, Oppenheimer had concluded plutonium could not be used in a gun design, and opted for implosion. The accelerated effort on an implosion design, codenamed Fat Man, began in August 1944 when Oppenheimer implemented a sweeping reorganization of the Los Alamos laboratory to focus on implosion. Two new groups were created at Los Alamos to develop the implosion weapon, X (for explosives) Division headed by George Kistiakowsky and G (for gadget) Division under Robert Bacher. The new design that von Neumann and T (for theoretical) Division, most notably Rudolf Peierls, had devised used explosive lenses to focus the explosion onto a spherical shape using a combination of both slow and fast high explosives.
The design of lenses that detonated with the proper shape and velocity turned out to be slow, difficult and frustrating. Various explosives were tested before settling on composition B as the fast explosive and baratol as the slow explosive. The final design resembled a soccer ball, with 20 hexagonal and 12 pentagonal lenses, each weighing about 80 pounds (36 kg). Getting the detonation just right required fast, reliable and safe electrical detonators, of which there were two for each lens for reliability. It was therefore decided to use exploding-bridgewire detonators, a new invention developed at Los Alamos by a group led by Luis Alvarez. A contract for their manufacture was given to Raytheon.
To study the behavior of converging shock waves, Robert Serber devised the RaLa Experiment, which used the short-lived radioisotopelanthanum-140, a potent source of gamma radiation. The gamma ray source was placed in the center of a metal sphere surrounded by the explosive lenses, which in turn were inside in an ionization chamber. This allowed the taking of an X-ray movie of the implosion. The lenses were designed primarily using this series of tests. In his history of the Los Alamos project, David Hawkins wrote: "RaLa became the most important single experiment affecting the final bomb design".
Within the explosives was the 4.5-inch (110 mm) thick aluminum pusher, which provided a smooth transition from the relatively low density explosive to the next layer, the 3-inch (76 mm) thick tamper of natural uranium. Its main job was to hold the critical mass together as long as possible, but it would also reflect neutrons back into the core. Some part of it might fission as well. To prevent predetonation by an external neutron, the tamper was coated in a thin layer of boron. A polonium-beryllium modulated neutron initiator, known as an "urchin" because its shape resembled a sea urchin, was developed to start the chain reaction at precisely the right moment. This work with the chemistry and metallurgy of radioactive polonium was directed by Charles Allen Thomas of the Monsanto Company and became known as the Dayton Project. Testing required up to 500 curies per month of polonium, which Monsanto was able to deliver. The whole assembly was encased in a duralumin bomb casing to protect it from bullets and flak.
The ultimate task of the metallurgists was to determine how to cast plutonium into a sphere. The difficulties became apparent when attempts to measure the density of plutonium gave inconsistent results. At first contamination was believed to be the cause, but it was soon determined that there were multiple allotropes of plutonium. The brittle Î± phase that exists at room temperature changes to the plastic Î² phase at higher temperatures. Attention then shifted to the even more malleable Î´ phase that normally exists in the 300 °C to 450 °C range. It was found that this was stable at room temperature when alloyed with aluminum, but aluminum emits neutrons when bombarded with alpha particles, which would exacerbate the pre-ignition problem. The metallurgists then hit upon a plutonium-gallium alloy, which stabilized the Î´ phase and could be hot pressed into the desired spherical shape. As plutonium was found to corrode readily, the sphere was coated with nickel.
The work proved dangerous. By the end of the war, half the experienced chemists and metallurgists had to be removed from work with plutonium when unacceptably high levels of the element appeared in their urine. A minor fire at Los Alamos in January 1945 led to a fear that a fire in the plutonium laboratory might contaminate the whole town, and Groves authorized the construction of a new facility for plutonium chemistry and metallurgy, which became known as the DP-site. The hemispheres for the first plutonium pit (or core) were produced and delivered on 2 July 1945. Three more hemispheres followed on 23 July and were delivered three days later.
TrinityBecause of the complexity of an implosion-style weapon, it was decided that, despite the waste of fissile material, an initial test would be required. Groves approved the test, subject to the active material being recovered. Consideration was therefore given to a controlled fizzle, but Oppenheimer opted instead for a full-scale nuclear test, codenamed "Trinity".
In March 1944, planning for the test was assigned to Kenneth Bainbridge, a professor of physics at Harvard, working under Kistiakowsky. Bainbridge selected the bombing range near Alamogordo Army Airfield as the site for the test. Bainbridge worked with Captain Samuel P. Davalos on the construction of the Trinity Base Camp and its facilities, which included barracks, warehouses, workshops, an explosive magazine and a commissary.
Groves did not relish the prospect of explaining the loss of a billion dollars worth of plutonium to a Senate committee, so a cylindrical containment vessel codenamed "Jumbo" was constructed to recover the active material in the event of a failure. Measuring 25 feet (7.6 m) long and 12 feet (3.7 m) wide, it was fabricated at great expense from 214 long tons (217 t) of iron and steel by Babcock & Wilcox in Barberton, Ohio. Brought in a special railroad car to a siding in Pope, New Mexico, it was transported the last 25 miles (40 km) to the test site on a trailer pulled by two tractors. By the time it arrived, however, confidence in the implosion method was high enough, and the availability of plutonium was sufficient, that Oppenheimer decided not to use it. Instead, it was placed atop a steel tower 800 yards (730 m) from the weapon as a rough measure of how powerful the explosion would be. In the end, Jumbo survived, although its tower did not, adding credence to the belief that Jumbo would have successfully contained a fizzled explosion.
A pre-test explosion was conducted on 7 May 1945 to calibrate the instruments. A wooden test platform was erected 800 yards (730 m) from Ground Zero and piled with 100 long tons (100 t) of TNT spiked with nuclear fission products in the form of an irradiated uranium slug from Hanford, which was dissolved and poured into tubing inside the explosive. This explosion was observed by Oppenheimer and Groves's new deputy commander, Brigadier General Thomas Farrell. The pre-test produced data that proved vital for the Trinity test.
For the actual test, the weapon, nicknamed "the gadget", was hoisted to the top of a 100-foot (30 m) steel tower, as detonation at that height would give a better indication of how the weapon would behave when dropped from a bomber. Detonation in the air maximized the energy applied directly to the target, and generated less nuclear fallout. The gadget was assembled under the supervision of Norris Bradbury at the nearby McDonald Ranch House on 13 July, and precariously winched up the tower the following day. Observers included Bush, Chadwick, Conant, Farrell, Fermi, Groves, Lawrence, Oppenheimer and Tolman. At 05:30 on 16 July 1945 the gadget exploded with an energy equivalent of around 20 kilotons of TNT, leaving a crater of Trinitite (radioactive glass) in the desert 250 feet (76 m) wide. The shock wave was felt over 100 miles (160 km) away, and the mushroom cloud reached 7.5 miles (12.1 km) in height. It was heard as far away as El Paso, Texas, so Groves issued a cover story about an ammunition magazine explosion at Alamogordo Field.
PersonnelIn June 1944, the Manhattan Project employed some 129,000 workers, of whom 84,500 were construction workers, 40,500 were plant operators and 1,800 were military personnel. As construction activity fell off, the workforce declined to 100,000 a year later, but the number of military personnel increased to 5,600. Procuring the required numbers of workers, especially highly skilled workers, in competition with other vital wartime programs proved very difficult. In 1943, Groves obtained a special temporary priority for labor from the War Manpower Commission. In March 1944, both the War Production Board and the War Manpower Commission gave the project their highest priority.
Tolman and Conant, in their role as the project's scientific advisers, drew up a list of candidate scientists and had them rated by scientists already working on the project. Groves then sent a personal letter to the head of their university or company asking for them to be released for essential war work. At the University of Wisconsin''Madison, Stanislaw Ulam gave one of his students, Joan Hinton, an exam early, so she could leave to do war work. A few weeks later, Ulam received a letter from Hans Bethe, inviting him to join the project. Conant personally persuaded the explosives expert George Kistiakowsky to join the project.
One source of skilled personnel was the Army itself, particularly the Army Specialized Training Program. In 1943, the MED created the Special Engineer Detachment (SED), with an authorized strength of 675. Technicians and skilled workers drafted into the Army were assigned to the SED. Another source was the Women's Army Corps (WAC). Initially intended for clerical tasks handling classified material, the WACs were soon tapped for technical and scientific tasks as well. On 1 February 1945, all military personnel assigned to the MED, including all SED detachments, were assigned to the 9812th Technical Service Unit, except at Los Alamos, where military personnel other than SED, including the WACs and Military Police, were assigned to the 4817th Service Command Unit.
An Associate Professor of Radiology at the University of Rochester School of Medicine, Stafford L. Warren, was commissioned as a colonel in the United States Army Medical Corps, and appointed as chief of the MED's Medical Section and Groves' medical advisor. Warren's initial task was to staff hospitals at Oak Ridge, Richland and Los Alamos. The Medical Section was responsible for medical research, but also for the MED's health and safety programs. This presented an enormous challenge, because workers were handling a variety of toxic chemicals, using hazardous liquids and gases under high pressures, working with high voltages, and performing experiments involving explosives, not to mention the largely unknown dangers presented by radioactivity and handling fissile materials. Yet in December 1945, the National Safety Council presented the Manhattan Project with the Award of Honor for Distinguished Service to Safety in recognition of its safety record. Between January 1943 and June 1945, there were 62 fatalities and 3,879 disabling injuries, which was about 62 percent below the rate of private industry.
SecrecyA 1945 Life article estimated that before the Hiroshima and Nagasaki bombings "[p]robably no more than a few dozen men in the entire country knew the full meaning of the Manhattan Project, and perhaps only a thousand others even were aware that work on atoms was involved." The magazine wrote that the more than 100,000 others employed with the project "worked like moles in the dark". Warned that disclosing the project's secrets was punishable by 10 years in prison or a $10,000 ($131,000 today) fine, they saw enormous quantities of raw materials enter factories with nothing coming out, and monitored "dials and switches while behind thick concrete walls mysterious reactions took place" without knowing the purpose of their jobs.
Oak Ridge security personnel considered any private party with more than seven people as suspicious, and residents'--who believed that US government agents were secretly among them'--avoided repeatedly inviting the same guests. Although original residents of the area could be buried in existing cemeteries, every coffin was reportedly opened for inspection. Everyone, including top military officials, and their automobiles were searched when entering and exiting project facilities. One Oak Ridge worker stated that "if you got inquisitive, you were called on the carpet within two hours by government secret agents. Usually those summoned to explain were then escorted bag and baggage to the gate and ordered to keep going." Nonetheless, despite being told that their work would help end the war and perhaps all future wars, not seeing or understanding the results of their often tedious duties'--or even typical side effects of factory work such as smoke from smokestacks'--and the war in Europe ending without the use of their work, caused serious morale problems among workers and caused many rumors to spread. One manager stated after the war:
Well it wasn't that the job was tough ... it was confusing. You see, no one knew what was being made in Oak Ridge, not even me, and a lot of the people thought they were wasting their time here. It was up to me to explain to the dissatisfied workers that they were doing a very important job. When they asked me what, I'd have to tell them it was a secret. But I almost went crazy myself trying to figure out what was going on.
Another worker told of how, working in a laundry, she every day held "a special instrument" to uniforms and listened for "a clicking noise". She learned only after the war that she had been performing the important task of checking for radiation with a geiger counter. To improve morale among such workers Oak Ridge created an extensive system of intramural sports leagues, including 10 baseball teams, 81 softball teams, and 26 football teams.
CensorshipVoluntary censorship of atomic information began before the Manhattan Project. After the start of the European war in 1939 American scientists began avoiding publishing military-related research, and in 1940 scientific journals began asking the National Academy of Sciences to clear articles. William L. Laurence of The New York Times, who wrote an article for The Saturday Evening Post in September 1940 on atomic fission, later learned that government officials asked librarians nationwide in 1943 to withdraw the issue. The Soviets noticed the silence, however. In April 1942 nuclear physicist Georgy Flyorov wrote to Josef Stalin on the absence of articles on nuclear fission in American journals; this resulted in the Soviet Union establishing its own atomic bomb project.
The Manhattan Project operated under tight security lest its discovery induce Axis powers, especially Germany, to accelerate their own nuclear projects or undertake covert operations against the project. The government's Office of Censorship, by contrast, relied on the press to comply with a voluntary code of conduct it published, and the project at first avoided notifying the office. By early 1943 newspapers began publishing reports of large construction in Tennessee and Washington based on public records, and the office began discussing with the project how to maintain secrecy. In June the Office of Censorship asked newspapers and broadcasters to avoid discussing "atom smashing, atomic energy, atomic fission, atomic splitting, or any of their equivalents. The use for military purposes of radium or radioactive materials, heavy water, high voltage discharge equipment, cyclotrons." The office also asked to avoid discussion of "polonium, uranium, ytterbium, hafnium, protactinium, radium, rhenium, thorium, deuterium"; only uranium was sensitive, but was listed with other elements to hide its importance.
Soviet spiesMain article: Atomic spiesThe prospect of sabotage was always present, and sometimes suspected when there were equipment failures. While there were some problems believed to be the result of careless or disgruntled employees, there were no confirmed instances of Axis-instigated sabotage. However, on 10 March 1945, a Japanese fire balloon struck a power line, and the resulting power surge caused the three reactors at Hanford to be temporarily shut down. With so many people involved, security was a difficult task. A special Counter Intelligence Corps detachment was formed to handle the project's security issues. By 1943, it was clear that the Soviet Union was attempting to penetrate the project. Lieutenant Colonel Boris T. Pash, the head of the Counter Intelligence Branch of the Western Defense Command, investigated suspected Soviet espionage at the Radiation Laboratory in Berkeley. Oppenheimer informed Pash that he had been approached by a fellow professor at Berkeley, Haakon Chevalier, about passing information to the Soviet Union.
The most successful Soviet spy was Klaus Fuchs, a member of the British Mission who played an important part at Los Alamos. The 1950 revelation of Fuchs' espionage activities damaged the United States' nuclear cooperation with Britain and Canada. Subsequently, other instances of espionage were uncovered, leading to the arrest of Harry Gold, David Greenglass and Ethel and Julius Rosenberg. Other spies like George Koval and Theodore Hall remained unknown for decades. The value of the espionage is difficult to quantify, as the principal constraint on the Soviet atomic bomb project was a shortage of uranium ore. The consensus is that espionage saved the Soviets one or two years of effort.
Foreign intelligenceMain article: Alsos MissionIn addition to developing the atomic bomb, the Manhattan Project was charged with gathering intelligence on the German nuclear energy project. It was believed that the Japanese nuclear weapons program was not far advanced because Japan had little access to uranium ore, but it was initially feared that Germany was very close to developing its own weapons. At the instigation of the Manhattan Project, a bombing and sabotage campaign was carried out against heavy water plants in German-occupied Norway. A small mission was created, jointly staffed by the Office of Naval Intelligence, OSRD, the Manhattan Project, and Army Intelligence (G-2), to investigate enemy scientific developments. It was not restricted to those involving nuclear weapons. The Chief of Army Intelligence, Major General George V. Strong, appointed Boris Pash to command the unit, which was codenamed "Alsos", a Greek word meaning "grove".
The Alsos Mission to Italy questioned staff of the physics laboratory at the University of Rome following the capture of the city in June 1944. Meanwhile Pash formed a combined British and American Alsos mission in London under the command of Captain Horace K. Calvert to participate in Operation Overlord. Groves considered the risk that the Germans might attempt to disrupt the Normandy landings with radioactive poisons was sufficient to warn General Dwight D. Eisenhower and send an officer to brief his chief of staff, Lieutenant General Walter Bedell Smith. Under the codename Operation Peppermint, special equipment was prepared and Chemical Warfare Service teams were trained in its use.
Following in the wake of the advancing Allied armies, Pash and Calvert interviewed Fr(C)d(C)ric Joliot-Curie about the activities of German scientists. They spoke to officials at Union Mini¨re du Haut Katanga about uranium shipments to Germany. They tracked down 68 tons of ore in Belgium and 30 tons in France. The interrogation of German prisoners indicated that uranium and thorium were being processed in Oranienburg, 20 miles north of Berlin, so Groves arranged for it to be bombed on 15 March 1945.
An Alsos team went to Stassfurt in the Soviet Occupation Zone and retrieved 11 tons of ore from WIFO. In April 1945, Pash, in command of a composite force known as T-Force, conducted Operation Harborage, a sweep behind enemy lines of the cities of Hechingen, Bisingen and Haigerloch that were the heart of the German nuclear effort. T-Force captured the nuclear laboratories, documents, equipment and supplies, including heavy water and 1.5 tons of metallic uranium.
Alsos teams rounded up German scientists including Kurt Diebner, Otto Hahn, Walther Gerlach, Werner Heisenberg and Carl Friedrich von Weizs¤cker, who were taken to England where they were interned at Farm Hall, a bugged house in Godmanchester. After the bombs were detonated in Japan, the Germans were forced to confront the fact that the Allies had done what they could not.
Bombing of Hiroshima and NagasakiPreparationsStarting in November 1943, the Army Air Forces Materiel Command at Wright Field, Ohio, began Silverplate, the codename modification of B-29s to carry the bombs. Test drops were carried out at Muroc Army Air Field, California, and the Naval Ordnance Test Station at Inyokern, California. Groves met with the Chief of United States Army Air Forces (USAAF), General Henry H. Arnold, in March 1944 to discuss the delivery of the finished bombs to their targets. The only Allied aircraft capable of carrying the 17-foot (5.2 m) long Thin Man or the 59-inch (150 cm) wide Fat Man was the British Avro Lancaster, but using a British aircraft would have caused difficulties with maintenance. Groves hoped that the American Boeing B-29 Superfortress could be modified to carry Thin Man by joining its two bomb bays together. Arnold promised that no effort would be spared to modify B-29s to do the job, and designated Major General Oliver P. Echols as the USAAF liaison to the Manhattan Project. In turn, Echols named Colonel Roscoe C. Wilson as his alternate, and Wilson became Manhattan Project's main USAAF contact. President Roosevelt instructed Groves that if the atomic bombs were ready before the war with Germany ended, he should be ready to drop them on Germany.
The 509th Composite Group was activated on 17 December 1944 at Wendover Army Air Field, Utah, under the command of Colonel Paul W. Tibbets. This base, close to the border with Nevada, was codenamed "Kingman" or "W-47". Training was conducted at Wendover and at Batista Army Airfield, Cuba, where the 393d Bombardment Squadron practiced long-distance flights over water, and dropping dummy pumpkin bombs. A special unit known as Alberta was formed at Los Alamos under Captain William S. Parsons as part of the Manhattan Project to assist in preparing and delivering the bombs. Commander Frederick L. Ashworth from Alberta met with Fleet Admiral Chester W. Nimitz on Guam in February 1945 to inform him of the project. While he was there, Ashworth selected North Field on the Pacific Island Tinian as a base for the 509th Composite Group, and reserved space for the group and its buildings. The group deployed there in July 1945. Farrell arrived at Tinian on 30 July as the Manhattan Project representative.
Most of the components for Little Boy left San Francisco on the cruiser USS Indianapolis on 16 July and arrived on Tinian on 26 July. Four days later the ship was sunk by a Japanese submarine. The remaining components, which included six uranium-235 rings, were delivered by three C-54 Skymasters of the 509th Group's 320th Troop Carrier Squadron. Two Fat Man assemblies travelled to Tinian in specially modified 509th Composite Group B-29s. The first plutonium core went in a special C-54. A joint targeting committee of the Manhattan District and USAAF was established to determine which cities in Japan should be targets, and recommended Kokura, Hiroshima, Niigata and Kyoto. At this point, Secretary of WarHenry L. Stimson intervened, announcing that he would be making the targeting decision, and that he would not authorize the bombing of Kyoto on the grounds of its historical and religious significance. Groves therefore asked Arnold to remove Kyoto not just from the list of nuclear targets, but from targets for conventional bombing as well. One of Kyoto's substitutes was Nagasaki.
BombingsIn May 1945, the Interim Committee was created to advise on wartime and postwar use of nuclear energy. The committee was chaired by Stimson, with James F. Byrnes, a former US Senator soon to be Secretary of State, as President Harry S. Truman's personal representative; Ralph A. Bard, the Under Secretary of the Navy; William L. Clayton, the Assistant Secretary of State; Vannevar Bush; Karl T. Compton; James B. Conant; and George L. Harrison, an assistant to Stimson and president of New York Life Insurance Company. The Interim Committee in turn established a scientific panel consisting of Arthur Compton, Fermi, Lawrence and Oppenheimer to advise it on scientific issues. In its presentation to the Interim Committee, the scientific panel offered its opinion not just on the likely physical effects of an atomic bomb, but on its probable military and political impact.
At the Potsdam Conference in Germany, Truman was informed that the Trinity test had been successful. He told Stalin, the leader of the Soviet Union, that the US had a new superweapon, without giving any details. This was the first official communication to the Soviet Union about the bomb, but Stalin already knew about it from spies. With the authorization to use the bomb against Japan already given, no alternatives were considered after the Japanese rejection of the Potsdam Declaration.
On 6 August 1945, the 393d Bombardment Squadron B-29 Enola Gay, piloted and commanded by Tibbets, lifted off with Parsons on board as weaponeer, and Little Boy in its bomb bay. Hiroshima, the headquarters of the 2nd General Army and Fifth Division and a port of embarkation, was the primary target of the mission, with Kokura and Nagasaki as alternatives. With Farrell's permission, Parsons completed the bomb assembly in the air to minimize the risks during takeoff. The bomb detonated at an altitude of 1,750 feet (530 m) with a blast that was later estimated to be the equivalent of 13 kilotons of TNT. An area of approximately 4.7 square miles (12 km2) was destroyed. Japanese officials determined that 69% of Hiroshima's buildings were destroyed and another 6''7% damaged. About 70,000 to 80,000 people, of whom 20,000 were Japanese soldiers, or some 30% of the population of Hiroshima, were killed immediately, and another 70,000 injured.
On the morning of 9 August 1945, the B-29 Bockscar, piloted by the 393d Bombardment Squadron's commander, Major Charles W. Sweeney, lifted off with a Fat Man on board. This time, Ashworth served as weaponeer and Kokura was the primary target. Sweeney took off with the weapon already armed but with the electrical safety plugs still engaged. When they reached Kokura, they found cloud cover had obscured the city, prohibiting the visual attack required by orders. After three runs over the city, and with fuel running low, they headed for the secondary target, Nagasaki. Ashworth decided that a radar approach would be used if the target was obscured, but a last-minute break in the clouds over Nagasaki allowed a visual approach as ordered. The Fat Man was dropped over the city's industrial valley midway between the Mitsubishi Steel and Arms Works in the south and the Mitsubishi-Urakami Ordnance Works in the north. The resulting explosion had a blast yield equivalent to 21 kilotons of TNT, roughly the same as the Trinity blast, but was confined to the Urakami Valley, and a major portion of the city was protected by the intervening hills, resulting in the destruction of about 44% of the city. The bombing also crippled the city's industrial production extensively and killed 23,200-28,200 Japanese industrial workers and 150 Japanese soldiers. Overall, an estimated 35,000-40,000 people were killed and 60,000 injured.
Groves expected to have another atomic bomb ready for use on 19 August, with three more in September and a further three in October. Two more Fat Man assemblies were readied. The third core was scheduled to leave Kirtland Field for Tinian on 12 August. Robert Bacher was packaging it at the Ice House at Los Alamos when he received word that the Japanese had initiated surrender negotiations. Groves ordered the shipments suspended. On 11 August, he phoned Warren with orders to organize a survey team to report on the damage and radioactivity at Hiroshima and Nagasaki. A party equipped with portable Geiger counters arrived in Hiroshima on 8 September headed by Farrell and Warren, with Japanese Rear Admiral Masao Tsuzuki, who acted as a translator. They remained in Hiroshima until 14 September and then surveyed Nagasaki from 19 September to 8 October. This and other scientific missions to Japan would provide valuable scientific and historical data.
The necessity of the bombings of Hiroshima and Nagasaki became a subject of controversy among historians. Some questioned whether an "atomic diplomacy" would not have attained the same goals and disputed whether the bombings or the Soviet declaration of war on Japan was decisive. The Franck Report was the most notable effort pushing for a demonstration but was turned down by the Interim Committee's scientific panel. The Szilrd petition, drafted in July 1945 and signed by dozens of scientists working on the Manhattan Project, was a late attempt at warning President Harry S. Truman about his responsibility in using such weapons.
After the warSeeing the work they had not understood produce the Hiroshima and Nagasaki bombs amazed the workers of the Manhattan Project as much as the rest of the world; newspapers in Oak Ridge announcing the Hiroshima bomb sold for $1 ($13 today). Although the bombs' existence was public secrecy continued, and many workers remained ignorant of their jobs; one stated in 1946, "I don't know what the hell I'm doing besides looking into a '--'--'-- and turning a '--'--'-- alongside a '--'--'--. I don't know anything about it, and there's nothing to say". Many residents continued to avoid discussion of "the stuff" in ordinary conversation despite it being the reason for their town's existence.
In anticipation of the bombings, Groves had Henry DeWolf Smyth prepare a history for public consumption. Atomic Energy for Military Purposes, better known as the "Smyth Report", was released to the public on 12 August 1945. Groves and Nichols presented Army''Navy "E" Awards to key contractors, whose involvement had hitherto been secret. Over 20 awards of the Presidential Medal for Merit were made to key contractors and scientists, including Bush and Oppenheimer. Military personnel received the Legion of Merit, including the commander of the Women's Army Corps detachment, Captain Arlene G. Scheidenhelm.
At Hanford, plutonium production fell off as Reactors B, D and F wore out, "poisoned" by fission products and swelling of the graphite moderator known as the Wigner effect. The swelling damaged the charging tubes where the uranium was irradiated to produce plutonium, rendering them unusable. In order to maintain the supply of polonium for the urchin initiators, production was curtailed and the oldest unit, B pile, was closed down so at least one reactor would be available in the future. Research continued, with DuPont and the Metallurgical Laboratory developing a redox solvent extraction process as an alternative plutonium extraction technique to the bismuth phosphate process, which left unspent uranium in a state from which it could not easily be recovered.
Bomb engineering was carried out by the Z Division, named for its director, Dr. Jerrold R. Zacharias from Los Alamos. Z Division was initially located at Wendover Field but moved to Oxnard Field, New Mexico, in September 1945 to be closer to Los Alamos. This marked the beginning of Sandia Base. Nearby Kirtland Field was used as a B-29 base for aircraft compatibility and drop tests. By October, all the staff and facilities at Wendover had been transferred to Sandia. As reservist officers were demobilized, they were replaced by about fifty hand-picked regular officers.
Nichols recommended that S-50 and the Alpha tracks at Y-12 be closed down. This was done in September. Although performing better than ever, the Alpha tracks could not compete with K-25 and the new K-27, which had commenced operation in January 1946. In December, the Y-12 plant was closed, thereby cutting the Tennessee Eastman payroll from 8,600 to 1,500 and saving $2 million a month.
Nowhere was demobilization more of a problem than at Los Alamos, where there was an exodus of talent. Much remained to be done. The bombs used on Hiroshima and Nagasaki were like laboratory pieces; work would be required to make them simpler, safer and more reliable. Implosion methods needed to be developed for uranium in place of the wasteful gun method, and composite uranium-plutonium cores were needed now that plutonium was in short supply because of the problems with the reactors. However, uncertainty about the future of the laboratory made it hard to induce people to stay. Oppenheimer returned to his job at the University of California and Groves appointed Norris Bradbury as an interim replacement. In fact, Bradbury would remain in the post for the next 25 years. Groves attempted to combat the dissatisfaction caused by the lack of amenities with a construction program that included an improved water supply, three hundred houses, and recreation facilities.
Two Fat Man''type detonations were conducted at Bikini Atoll in July 1946 as part of Operation Crossroads to investigate the effect of nuclear weapons on warships. Able was detonated on 1 July 1946. The more spectacular Baker was detonated underwater on 25 July 1946.
After the bombings at Hiroshima and Nagasaki, a number of Manhattan Project physicists founded the Bulletin of the Atomic Scientists, which began as an emergency action undertaken by scientists who saw urgent need for an immediate educational program about atomic weapons. In the face of the destructiveness of the new weapons and in anticipation of the nuclear arms race several project members including Bohr, Bush and Conant expressed the view that it was necessary to reach agreement on international control of nuclear research and atomic weapons. The Baruch Plan, unveiled in a speech to the newly formed United Nations Atomic Energy Commission (UNAEC) in June 1946, proposed the establishment of an international atomic development authority, but was not adopted.
Following a domestic debate over the permanent management of the nuclear program, the United States Atomic Energy Commission (AEC) was created by the Atomic Energy Act of 1946 to take over the functions and assets of the Manhattan Project. It established civilian control over atomic development, and separated the development, production and control of atomic weapons from the military. Military aspects were taken over by the Armed Forces Special Weapons Project (AFSWP). Although the Manhattan Project ceased to exist on 31 December 1946, the Manhattan District would remain until it too was abolished on 15 August 1947.
CostManhattan Project costs through 31 December 1945SiteCost (1945 USD)Cost (2015 USD) % of totalOak Ridge$1.19 billion$15.6 billion700162900000000000062.9%Hanford$390 million$5.11 billion700120600000000000020.6%Special operating materials$103 million$1.35 billion70005500000000000005.5%Los Alamos$74.1 million$970 million70003900000000000003.9%Research and development$69.7 million$913 million70003700000000000003.7%Government overhead$37.3 million$488 million70002000000000000002.0%Heavy water plants$26.8 million$351 million70001400000000999991.4%Total$1.89 billion$24.8 billionThe project expenditure through 1 October 1945 was $1.845 billion, equivalent to less than nine days of wartime spending, and was $2.191 billion when the AEC assumed control on 1 January 1947. Total allocation was $2.4 billion. Over 90% of the cost was for building plants and producing the fissionable materials, and less than 10% for development and production of the weapons.
A total of four weapons (the Trinity gadget, Little Boy, Fat Man, and an unused bomb) were produced by the end of 1945, making the average cost per bomb around $500 million in 1945 dollars. By comparison, the project's total cost by the end of 1945 was about 90% of the total spent on the production of US small arms (not including ammunition) and 34% of the total spent on US tanks during the same period.
LegacyThe political and cultural impacts of the development of nuclear weapons were profound and far-reaching. William Laurence of the New York Times, the first to use the phrase "Atomic Age", became the official correspondent for the Manhattan Project in spring 1945. In 1943 and 1944 he unsuccessfully attempted to persuade the Office of Censorship to permit writing about the explosive potential of uranium, and government officials felt that he had earned the right to report on the biggest secret of the war. Laurence witnessed both the Trinity test and the bombing of Nagasaki and wrote the official press releases prepared for them. He went on to write a series of articles extolling the virtues of the new weapon. His reporting before and after the bombings helped to spur public awareness of the potential of nuclear technology and motivated its development in the United States and the Soviet Union.
The wartime Manhattan Project left a legacy in the form of the network of national laboratories: the Lawrence Berkeley National Laboratory, Los Alamos National Laboratory, Oak Ridge National Laboratory, Argonne National Laboratory and Ames Laboratory. Two more were established by Groves soon after the war, the Brookhaven National Laboratory at Upton, New York, and the Sandia National Laboratories at Albuquerque, New Mexico. Groves allocated $72 million to them for research activities in fiscal year 1946''1947. They would be in the vanguard of the kind of large-scale research that Alvin Weinberg, the director of the Oak Ridge National Laboratory, would call Big Science.
The Naval Research Laboratory had long been interested in the prospect of using nuclear power for warship propulsion, and sought to create its own nuclear project. In May 1946, Nimitz, now Chief of Naval Operations, decided that the Navy should instead work with the Manhattan Project. A group of naval officers were assigned to Oak Ridge, the most senior of whom was Captain Hyman G. Rickover, who became assistant director there. They immersed themselves in the study of nuclear energy, laying the foundations for a nuclear-powered navy. A similar group of Air Force personnel arrived at Oak Ridge in September 1946 with the aim of developing nuclear aircraft. Their Nuclear Energy for the Propulsion of Aircraft (NEPA) project ran into formidable technical difficulties, and was ultimately cancelled.
The ability of the new reactors to create radioactive isotopes in previously unheard-of quantities sparked a revolution in nuclear medicine in the immediate postwar years. Starting in mid-1946, Oak Ridge began distributing radioisotopes to hospitals and universities. Most of the orders were for iodine-131 and phosphorus-32, which were used in the diagnosis and treatment of cancer. In addition to medicine, isotopes were also used in biological, industrial and agricultural research.
On handing over control to the Atomic Energy Commission, Groves bid farewell to the people who had worked on the Manhattan Project:
Five years ago, the idea of Atomic Power was only a dream. You have made that dream a reality. You have seized upon the most nebulous of ideas and translated them into actualities. You have built cities where none were known before. You have constructed industrial plants of a magnitude and to a precision heretofore deemed impossible. You built the weapon which ended the War and thereby saved countless American lives. With regard to peacetime applications, you have raised the curtain on vistas of a new world.
^The reaction Teller was most concerned with was: 147N + 147N '' 2412Mg + 42He (alpha particle) + 17.7 MeV.^In Bethe's account, the possibility of this ultimate catastrophe came up again in 1975 when it appeared in a magazine article by H.C. Dudley, who got the idea from a report by Pearl Buck of an interview she had with Arthur Compton in 1959. The worry was not entirely extinguished in some people's minds until the Trinity test.^Natural self-sustaining nuclear reactions have occurred in the distant past.^The allusion here is to the Italian navigator Christopher Columbus, who reached the Caribbean in 1492.Citations
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