World War II: Atomic Bomb--The Manhattan Project

Figure 1.--Only faltering stepd wre taken toward an atomic bomb project until Pear Harbor (Devember 1942). Than the pace hanged almost overnight. Oak Ridge was an unkown small, quiet farming town of only about 3,000 people in eastern Tennesse. Suddenly in 1942 all that changed almost overnight. Oak Ridge became on of the most important location in the american World War II war effort. Gen. Leslie Groves selected Oak Ridge as the site for developing fissle material for the Mahattan Project. Oak Risge has only a small population to move out. it was near importat highway and rail lines and most importantly in ws near the new TVA Norris Dam proiing electrical energy and water in large quantities. By the end of the War it was a bustling metroplis of 45,000 people. Houes and basic facilities had to be built virtually overnight. Here a library truck brings books the children in 1944.

The American Manhattan Program was the largest weapons development program in history. It was initiated by President Roosevelt when work done by German physicists led to concern that the NAZIs might build an atomic bomb. Important scientists in 1939 concluded that German scientists had begun to develop an atomic bomb for the NAZIs. These scientists induced President Roosevelt to launch an American atomic bomb project. The project was, however, given serious attention only after the Japanese attack on Pearl Harbor bringing America into the war. General Leslie R. Groves (1896-1970), Deputy Chief of Construction of the U.S. Army Corps of Engineers, was assigned to oversee the project. The Manhattan Project us named after the New York borough where the first office headquarters was located and began June 1942. Groves had just completed another rush project, the construction of the Pentagon. He considered himself an astute judge of men and chose Robert J. Oppenheimer (1904-1967)to lead the scientific team. Oppenhimer was a respected, but relatively unknown theoretical physicist. Enrico Fermi and Leo Salard working in a converted squash court beneath the University of Chicago's carried out the first controlled nuclear reaction occurred confirming that nuclear fission could unleash huge amounts of energy. The major difficulty in building an atomic bomb was in obtaining the required quantity of fissionable material. A huge facility was built an Oak Ridge, Tennessee to separated the U-235 isotope needed for the bomb from the more common U-238 isotope. The Hanford Engineer Works was built in Washington to produce plutonium. Groves chose Los Alamos, New Mexico as a location to actually develop and assemble the bomb or "gadget" a it was called. This isolated town had by March 1943 been turned into a high-technology boomtown. The Y-12 Plant at Oak Ridge provided the bomb-grade U-235 used for the Little Boy bomb. The Harford plant provided the Plutonium used in the Fat Man bomb.

German Science

Germany in the early 20th century had the strongest scientific establishment in Europe. German scientists routinely received the largest number of Nobel prizes in scientific fields. And physics was one of the field that German scientists dominated. This did not change until the NAZIs seized power in 1933. After the NAZI seizure, Jewish scientists as well as anti-NAZIs were dismissed from their positions. After 1933, America became increasingly dominate in Nobel scientific awards. Despite a decline in German scientific dominance, the NAZIs still had access to the huge scientific establishment that had been built by Imperial Germany. The NAZIs drew heavily on this establishment for their weapons and armament program. Another factor was the weakening of academic standards in German schools and universities. This was a development that would have affected Germany in the long term, but did not have an immediate impact on the German scientific capability during World War II.

Kristallnacht (November 1938)

The NAZI campaign against Jews culminated in Kristallnacht, an brutal explosion of violence against Jews in Germany. Before Kristallnacht, the NAZIs had killed Jews in concentration camps and prisons behind closed doors. On Kristallnacht Jews were attacked and killed openly on the street or in their homes. There intentions cold no longer be doubted. The consequences for the atomic bomb project that among leading physicists were many Jews or anti-NAZIs. These men recognized the true nature of the NAZI regime more than others the potential danger of a NAZI atomic bomb. After Kristallnacht, even men who might have had moral qualms about building an atomic bomb, were prepared to do virtually anything to stop the NAZIs.

Nuclear Fission (December 1938)

German physicists Otto Hahn and Fritz Strassmann at the Kaiser Wilhelm Institute demonstrated the phenomenon of nuclear fission. Lise Meitner (1878-1968), an eminent scientist who became famous working at the neutron bombardment experiments with Otto Hahn and Fritz Strassmann (who both got the Nobel prize for physics, while Meitner did not). Meitner who was Jewish remained in Germany with her work until it was difficult to emigrate, but with the help of friends did manage to escape. NAZI Germany had an aggressive military weapons program. This discovery by German physicists raised the possibility of a NAZI German nuclear weapons program. This terrified the European scientists that knew Fascism first hand. The Luftwaffe was already being used to terrify Europe. The consequences of a NAZI Germany armed with nuclear weapons was too terrifying to imagine. One of the ironies of history was that militarily, Hiltler was obsessed with giantism, he wanted the largest tanks, battleships, artillery, and other weapons that could be built. Yet he rejected making a major effort to build the most powerful bomb--a war winning weapon. It is widely believed that his decision was in part because he considered nuclear physics "Jewish science" and drove from Germany and German domains the very people that could have built him the ultimate weapon.

World War II (September 1939)

NAZI Germany in the first years of the War seemed unstoppable. Hitler launches World War II with the invasion of Poland on September 1, 1939. The initial operations were dazzling successes for the Wehrmacht and Luftwaffe. Poland was smashed in a few weeks (1939). After Denmark, Norway was seized in a daring operation (1940), providing the Germany Kriegsmarine bases that greatly enhanced their operations. Then the stunning offensive in the West seized not only the low countries--but France. The French Army was the bulwark of the Allies war effort and was decimated by the Luftwaffe and Wehrmacht in weeks (1940). The Wehrmacht next launched a stunning attack on Yugoslavia and Greece (1941). Then Hitler launched the operation he had dreamed of for years, the invasion of the Soviet Union which at first appeared to be a huge success.

German Atomic Bomb Project

The Germans initially had some advantages in the race to build an atomic bomb and through 1941 led in the race. The invasion of Norway 1940 gave them possession to heavy water plants. They had access to uranium ore. The Germans also possessed a nearly completed cyclotron. Germany despite 10 years of NAZI rule still possessed capable scientists and engineers and what many believed was the world's most important chemical engineering industry. There were many factors that doomed the German atomic bomb program. The major factor was that building an atomic was an enormous undertaking requiring the massive allocation of resources. Germany never allocated the needed resources. There were several reasons for this. Perhaps the two greatest were the success in the early years of the War which led the Germans to believe that they were going to win the War without major economic sacrifices or expensive new weapon systems. Also Hitler was never convinced that the atomic bomb was a practical weapon. Some claim that the chief theoretical physicist (Heisenberg) deliberately pursued unproductive directions to prevent the NAZIs from building an atomic bomb. [Powers] This is intensely debated by historians. [Pais] Heisenberg visited noted Danish physicist Niels Bohr in occupied Denmark (September 1941). This is perhaps the most disputed scientific meeting in history. Bohr and Heisenberg have very different accounts of their meeting. Heisenberg after the War maintained his purpose was to broker a deal between scientists on both sides not to pursue an atomic bomb. Bohr strongly disputes this. Given that the NAZIs were not actively pursuing a bomb, many contend that Heisenberg's purpose was espionage. [Corwell] Bohr escaped from Denmark to Sweden (August 1943), and subsequently to London, and on to Los Alamos. An important NAZI scientist (Lenard) argued that nuclear/Einsteinian theory was degenerate "Jewish science" which helped to deny nuclear science the huge allocation of resources needed to build a bomb. Jews were an especially important component of the German physics community. The NAZIs thus seriously weakened Germany's ability to build a bomb. In this regard it should be remembered that the American Manhattan Project was an international effort, including not only American and British scientists, but scientists from countries overrun by the NAZIs. [Rhodes] There were as was common in NAZI Germany, serious internal bureaucratic struggles. An important scientific eerror also impeded progress. As the War began to turn against Germany, resources became more difficult to obtain and the bomb project required a massive industrial effort. In addition, the allied bombing campaign further complicating any important industrial project.

Refugees from the NAZIs

The NAZI campaign against the Jews began almost as soon as Hitler seized power in Germany. Even respected scientists were quickly dismissed from positions at universities and research institutes. Many of these individuals were able to emigrate and pursue their careers in America, France, and Britain. While many German Jews were unable to get visas, especially after Kristallnacht. Many scientists had the international contacts needed to obtain visas and most left Germany before it became more difficult to get out. This significantly increased the pool of talented scientists available to the American atomic bomb program. Some of the best known were Hans Bethe (Alsatian-German Jew), Albert Einstein (German Jew), Enrico Fermi (Italian with Jewish wife), Lise Meitner (Austrian Jew), Leo Szilard (Hungarian Jew working in Germany), Edward Teller (Hungarian Jew working in Germany), and Eugene Wigner (Hungarian Jew working in Germany). Some like Bethe did not look on himself as a Jew. Some authors believe that the dismissal of competent scientists and appointment of Party hacks was a major reason in the failure of the German bomb program. [Walker] Many of these nuclear scientists emigrated early in the NAZI era when the NAZIs were primarily concerned with dismissing Jews from universities and other official positions. Fremi came much later and managed to escape with his wife when he was allowed to go to Sweden to accept a Nobel Prize. Lise Meitner (1878-1968), escaped to Sweden just before the War with the help of Niels Bohr (another Nobel laureate). She later continued to work in the United States. History is full of unintended consequences. The Jews were essentially an easy target for Hitler and his NAZI thugs. Few expected retribution for their actions against the Jews. There were indeed few adverse domestic consequences. In fact the NAZIs probably gained support for these actions from anti-Semites as well as those who benefited from the jobs opened up and the property seized. The NAZI anti-Semitic campaign not only helped President Roosevelt build support for his policies opposing the NAZIs, but help with providing the United States scientific talent which help build the atomic bomb. If the NAZIs had not surrendered in May 1945, the atomic bomb could have been used on Germany.

Anti-NAZI Warriors

The unfortunate image of World war II Jews is thAt they were passive victims of the NAZIs who made no ffort to resist. This is untrue, but as a small minority in a world awash with with anti-Semtism, opportinities to resist a totalitarian police state were limited. There was, however, one major exception--Jewish niclear pysicists. Many were German or until Hitler part of the wider German academic community. As Max Plank wrned, Hitler, he was disarming Germany in physics. Actually he was doing more than that. He was turning these individuals from pacifists like Einstrin or largely wordly humanitarians into anti-NAZI warriors who decided to use their capabilities to build the atomoc bomb. This was a huge transition. Most conceived of nuclear physics as offering tremendous emense peaceful uses to aid human progress. Only Hitler's evil which each experienced and observed comvinced them to turn their 'beauticul' science to mlitary use. Lise Meitner was an exception. While narrowly missing the Holocaut, she refused to work on the bomb project. Even Einstein, a life-long pacifist, decided that America should build the bomb because not only of Hitler's evil, but because the Germans were ahead of the Allies and had the capabilities of building a bomb. Hungarian Jewish physicist Leo Szilard convinced Einstein to write to Presisent Roosevelt, in effect launching the Manhattan Project (1939). Szilard also worked with Italian phsicist Enrico Fermi (who had a Jewish wife) to build the first nuclear ractor (pile) and achieved the first chain reaction (1942). Paul Wigner was another Hungarian Jewish scienist close to Szilard. Other Jewish emigre scientusts included Felix Bloch (Swiss), Niels Bohr (Danish), Klaus Fuchs (who passed information to the KGB), James Franck, Otto Frisch, Rudolph Peierls, and Edward Teller (Hunarian). We should mention that many of these men were not religious Jews, some like Bohr were raised Christians. Bur the NAZI Nuremberg Race Laws defined Jews as having two Jewish grandparents, regardless of the individuals professed religion. Not all the Jewish pysicists working to build the bomb were emigre scienists. This included the scientific leader of the Manhattan Project--Robert Opejeimer. Other American Jews working on the project included David Bohm. As with non-Jewish scientists, Opeheimer and others would have resisted building an atomic bomb had it not been for Hitler's evil and liklihood that the Germans were building a bomb.

President Roosevelt (1939)

President Roosevelt saw virtually from the first days of his presidency that Hitler and the NAZIs represented a mortal danger to America the other democracies. Much of his foreign policy efforts during the 1930s was involved in guiding American public opinion to see the threat posed by the NAZIs and adopting the necessary measures to confront the NAZIs. He was confront by a powerful and vocal isolationist opposition led by the America First Committee. Even so he managed to secure the passage of major initiatives to build a Two Ocean Navy, massive air forces, and a huge army

First Einstein Letter (August 2-October 11, 1939)

Albert Einstein was one of the scientists who left Germany when Hitler and the NAZIs seized power. Einstein was one of the first to leave (1933). He renounced his German citizenship and moved to Princeton. One historian calls Einstein and the European scientists who worked on the atomic bomb, "Hitler's gift to America". [Morgan, p. 514.] The scientists included Hans Bethe, Enrico Fermi, Leo Szilard, Edward Teller, John von Neumann, Stanislaw Ulman, and others. These and American scientists in 1939 concluded that German scientists had begun to develop an atomic bomb for the NAZIs. Of course the very idea of an atomic bomb was unknown to not only the general public, but even American political and military officials. Szilard was perhaps the most politically astute of the emigre scientists. Erico Fermi had met with Werner Heisenberg when the German scientst had visited America (June-July 1939). Fermi tried to convince him to defect. Heisenberg refused and his attitude shocked Fermi. [Schwartz] It is at this point he concluded that the Germans were going to build nucler weapons and that America must do so first. The question became how to engage the American Government. Here Szilard took th the initative. He realized that European scientist with funny accenta were not going to have much of an impact on American officaldom. Convincing officials to spend billions on what sounded like a Buck Rigers project was going to take real clout. Szilard understood that Albert Einstein might just be able to do so. Einstein by this time generally regarded as the greatest physicist of modern times and a refugee from the NAZIs. But he was also a determined pacifist. Szilard went to see Einstein and they discussed both the situation in Europe and the not only the probability that the NAZIs would build a bomb, but they were well ahead of the Allies. Only the spectre of a NAZI bomb moved Eistein off his fervet devotion to pacifism. Einstein immediately grasped the situation and despite his pacifism agreed to sign a letter to President Roosevelt recommending the United States explore the possibility of a nuclear weapon. Szilard drafted the letter abnd Einstein signed it. Einstein had a reputation that could not be easily dismissed. Einstein su\igned the letter (August 2)). They could not just mail the letter to the President. Szilard chose Alexander Sachs to deliver the letter, but it was sometime before Sachs could get to see the President. The letter was delivered (October 11). It read, "The new phenomenon would also lead to the construction of bombs, and it is conceivable--though much less certain--that extremely powerful bombs of a new type may thus be constructed. A single bomb of this type, carried by boat or exploded in a port, might very well destroy the whole port together with towns of the surrounding territory. However, such bombs might very well prove to be too heavy for transportation by air." [Morgan, pp. 514-515.]

Roosevelt's Reaction

Szilard was absolutely correct about Einstein. The President was indeed interested and impressed by the fact that Einstein had endorsed the idea. President Roosevelt had an inquiring mind. As Assistant Secretary of the Navy he dealt with inventors, some crack pots and some with useful ideas, such as a magnetic firing devices for mines. He also dealt with crack pots as an investor in the 1920s and lost some money in the process. He was intrigued with new ideas and of course Einstein's signature coul not hve impressed him. He wrote "this requires action" on the instein letter and passed it on to Pa Watson. The result was the creation of an "Advisory Committee on Uranium"--the precursor to an American atomic bomb project.

The British

The idea of an atomic bomb also emerged in Britain. Again it was refugee scientist who conceived and promoted the idea. The Austrian physicist Otto Frisch working with Lise Meitner, A German Jew who narrowly managed to escape the NAZIS, had accuately described what happens when a uranium atom is split. Frisch also escaped the NAZIs and reached Britain and was working at Birmingham University. He was staying with a long-time friend, physicist Rudolf Peierls--another emogre scientist. As a result of their work, they concluded that an atomic bomb could be built. It was Frisch who coined the term nuclear fission. They jointly authored a paper describing the process and took it to the British authorities. This was the first actual plan for building an atomic bomb. Churchill was also intrigued with scince and weaponry. The British set up a committee to work on a bomb project (April 1940). The British did not have the enormous resources needed to build an atomic bomb. The Americans did, but were undecided. The British helped to convince the Americans that this was a project of great importance. The Manhattan Project would become a joint Anglo-American project with British scientists playing an important role. One of those scientists would pass on important information to the Soviets.

Military Response

While the President showed interest, the U.S. military did not take the project seriously. The assignment to follow up was given to the ordinance divisions of the Army and Navy. They considered this a Buck Rogers futuristic concept that was not practical. As result, no real steps were initially taken by the military to pursue the project.

Vannevar Bush

A group of civilian scientists because of the military's lack of interest took over the project. Vannevar Bush was the President's scientific adviser and who headed the National Defense Research Committee assumed responsibility. Bush discussed the project with Sir Henry Tizard, Chairman of the British Committee of Air Defense. Bush decided that the atomic project needed to be given great priority. This was not only because the project was scientifically valid, but because it was feared that the NAZIs were actively pursuing a bomb project.

Preliminary Committees

President Roosevelt also created the Advisory Committee on Uranium a committee chaired by Lyman J. Bridges, Director of the National Bureau of Standards. The Committee met (October 21). It included Leo Szilard, Eugene Wihne (a Budapest physicist), and Enrico Fermi (Nobel prize winning Italian physicist). The physicists on the Committee asked for $2,000 to begin their work. The military members were skeptical of the physicists. Their foreign accents did not help. Col. K.R. Adamson who represented the Army saw the whole enterprise a waste of time. He explained that it usually took two wars to perfect weapons and that any way the critical factor in war was troop morale, not weapons. Wigner irritated at such appalling ignorance, suggest that if this was true than perhaps the thing to do was to reduce the Army budget. Adamson agreed to the $2,000. [Morgan, p. 515.] This was the beginning of the Manhattan Project, the most ambitious undertaking of the War. The Committee was renamed the Advisory Committee on Uranium (April 1940). Szilard and Fermi were excluded. Officials thought that if the Committee included aliens that a Congressional investigation might result. The Committee approved a contract to develop the Fermi-Szilard system (November 1940). After the decesion to pursue the project as a priority was made, this project was transferred to the University of Chicago (February 1942). Finally the program was moved to Oak Ridge, Tennessee and Los Alamos, New Mexico. [Morgan, p. 515.]

The Decision (October 9, 1941)

President Roosevelt in great secrecy made one of the most momentous decisions of the 20th century. Scientist adviser Vannevar Bush and Agriculture Secretary Henry Wallace brought the project to the President's attention. He and Secretary Wallace met with the President (October 9, 1941). Bush expressed concern about German research, but told the President that it was not know what Progress the Germans had made. The project was both speculative and would be extremely expensive. The President acted decisively with little hesitation after receiving the Bush report. He made one of the most significant decisions of the 20th century. With only minimal discussion the President decided to pursue the project with a high priority. [Black, pp. 665-66.]


President Roosevelt persuaded Speaker Rayburn to push through the necessary apropriations without Congressional scrutiny. Speaker Rayburn certified to the House that he and the President considered the project vital for national defense and was too sensitive to even be discussed in closed sessions. A massive appropriation was approved.

Top Policy Committee

The President set up the Top Policy Committee (October 9, 1941). The TPC was made up of General Marshall, Harvard President James B. Connat, Secretary Stimson, Secretary Wallace (chosen because he was a scientist), and scientist Vannevar Bush. The TPC actually met only a few times. It operated total secrecy. As it developed, it provided a platform to explore scientific initiatives. The major initiative pursued proved to be the atomic bomb project which became known as the Manhattan Project. The TPC reported directly to the President.

Pearl Harbor (December 1941)

The decision to pursue the project was taken only 2 moths before the Japanese attack on Pearl Harbor bringing America into the war. he NAZI Blitzkrieg in Europe completed a very different mindset in American than existed in Germany. American officials did not doubt that the Germans had the ability to build a bomb or lack the willingness to use it. Thus the reverses of the early years of the war helped to create the conditions that induced President Roosevelt to approve an atomic bomb project in the same way that the early German victories caused Hitler to take little interest in a vastly expensive project that he did not even understand. By the time of the Japanese attack, the atomic bomb project had been approved and Congressional funding authorized.

The Project (1942)

The American Manhattan Program was the largest weapons development program in history. General Leslie R. Groves (1896-1970), Deputy Chief of Construction of the U.S. Army Corps of Engineers, was assigned to oversee the project. The Manhattan Project us named after the New York borough where the first office headquarters was located and began June 1942. Groves had just completed another rush project, the construction of the Pentagon. He considered himself an astute judge of men and chose Robert J. Oppenheimer (1904-1967) to lead the scientific team. Oppenhimer was a respected, but relatively unknown theoretical physicist. Oppenheimer's politics are a matter of extensive debate. It is know that as a Jew, he despised the NAZIs and the atrocities against European Jews.

Controlled Nuclear Reaction: Chicago Pile No. 1 (December 1942)

It was the Americans who achieved the first controlled nuclear reaction. Dr. Enrio Fermi received the Nobel Prize in Physics (1938). Fermi had political problems with Mussolini and Fascism. And he had a Jewish wife. He obtained an appoitment with the University of Chicago deparment of metallurgy. Fermi had encouraged Einstein to write to President Roosevelt (October 1939). At the same time, the University of Chicago fielded one of the worst teams in American football history. University president Robert Maynard Hutchins decided to end the football program and famously said, "Football has the same relation to education that bullfighting has to agriculture." This left the large University Amos Alonzo Stagg stadium vacant. Einstein's letter to Presidebt Roosevelt had born fruit. And the Japanese attack on Pearl Harbor had lent a sence of urgency to the project. Thus with Government funding in hand, Fermi requeted permission from the University to carry out an important experiment for the U.S. Army. He provided no details, but the University quickly granted permission. Work began and truck loads of material soon began arriving in as much secrecy as could be maintained in the center of Chicago (Summer 1942). Leo Szilard, another refugee from European Fascism, was on Fermi's team. They worked in a converted squash court beneath the football stands. They assembled a nuclear reactor using a graphite pile and uranium balls. The end result was Chicago Pile No. 1. Fermi and his colleages achieved the world's first self-sustaining nuclear reaction (December 1942). Fermi and Salard confirmed that nuclear fission could unleash huge amounts of energy. It was the first major step in the Manhattan Project.

NAZI-Japanese Scientific Cooperation

Unlike the Anglo-American relationship, there sees to have been relsatively limited scientific cooperation between Germsany and Japan. What did occur was primarily German technology delivered to Japan. The Germans wanted to be paid. And they were concerned about the future relationship between the two countries. As the War went against Germany, the Germans were more willing to transfer technology. The problem was how to transfer it. Mine laying submarines were converted to carry cargos. We know that shipments took place, because one of the submarines, the U-234, surrended to the U.S. Navy after the NAZIs surrenderd and it contained enriched uranium. Just what cargos got through to Japan is not known.

Japanese Atomic Program

There are many unanswered questions about the German atomic bomb program. Even less is known about the Japanese program. The Japanese were also interested in nuclear weapons. Japan had nuclear scientists who learned about the German expeiments and were aware of the weapons potential. Both the Japanese Army and Navy has small atomic weapons program. There is considerable controversy concening the progress made. The Japanese began mining uranium at Konan, North Korea. The mine an research facility was seized by the Soviets after they declared war on Japan (August 1945). Konan is now the source of the uranium for North Korea's atomic bombs. Unlike the Anglo-American relationship, there sees to have been relatively limited scientific cooperation between Germsany and Japan. What did occur was primarily German technology delivered to Japan. The Germans at first wanted to be paid. And they were concerned about the future relationship between the two countries. As the War went against Germany, the Germans were more willing to transfer technology. The problem was how to transfer it. Mine laying submarines were converted to carry cargos. We know that shipments took place, because of German accounts and the fact that German submarine crews were found in Japan after the War. And more importantly, one of the submarines, the U-234, surrended to the U.S. Navy after the NAZIs surrenderd (May 1945). It contained enriched uranium as part of the cargo. Just what cargos got through to Japan earlier is not known with any surity. The U-234 incident clearly shows that uranium was a priority concern of the Japanese by the end of the War.

Obtaining Uranium

When World War II began, uranium was a liite used metal. There were industrial used for uranium ore known as pitchbled. The primary value was to obtain radium, a byproducr of the radioactive decay of uranium. The uranium itself was byproducr ysed to create yellow paint pigment. The principal mines at the time of World War II were located in the Belgian Congo, Canada, Czechoslovakia, and United States (Colorado). The Germans obtained possession of the Czech mine when they invaded and occupied the country (March 1939). The Germans also invaded Belgium (May 1940) and obtained stocks of uranium ore located there. They did not control, however, the source of the Belgian uranium.--the Belgian Congo. Authorities in the Belgian Congo declared their loyalty to the London Governmnt-in-exile. Thus the Manhattan Project would have access to mines in the Belgian Congo, Canada, and the United States. Surprisingly, a Belgian citizen had moved ore from the Congo mine to warehouse in New York. The mine in colorado had been closed and had to be reopened. The ores mined in Colorado were mixed vanadium and uranium. Possession of uranium ore was, however, only the first step. Refining the ore to enrich it (increase the percentage of the U-235 isotope) was perhaps the most difficult problem faced by the Manhattan Project. Another source of uranium proved to be the Germans when the U-234 surrendered at the end of the War (May 1945). They were attemoting to get the uranium to their Axis ally. This was particularly importaht because it was already enriched uranium. We have not yet, however been able to authorutatively determine the level of enrichment.

Fissionable Material

The major difficulty in building an atomic bomb was in obtaining the required quantity of fissionable material. The enormous effort required to produce weapons grade material is one of the principal reasons that the Germans did not initiate a aggressive atomic bomb project. A huge facility was built an Oak Ridge, Tennessee to separated the U-235 isotope needed for the bomb from the more common U-238 isotope. The ratio in nature is 1 to 29. Separating U-235, however, is an enormously difficult undertaking. Two methods were developed, electro-magnetic and gaseous diffusion. The first step in building the bomb was to build the plants needed to produce bomb-grade uranium. Here the scientists initially eared by estimating 200 kg of uranium was needed. This was 10 times the amount needed. The wartime emergency was so great that construction of the calutrons at Oak Ridge were begun even before the plans were finished. There was no time for pilot plants. As a result, numerous problems were encountered such as electro-magnets pulling nails out of the wall. The plant using electro-magentas was Y12. Because the output of a calutron was only a few months, 1,152 calutrons were eventually built. Another facility, K25 used the gaseous diffusion method. The plant was to have the largest area of any building ever constructed--2 million square feet. The energy demands were staggering, for a time 10 percent of the entire electrical output of the United States. The Hanford Engineer Works was built in Washington to produce plutonium.


World War II histories addressing the atmic bombs generally focus on uranium. But even more important ptoved to be plutonium. Understanding this requires some understanding of nuclear physics. Plutonium is a transuranic radioactive element that is higly dangerous. The chenmcal symbol Pu and atomic number 94. It does not occur in nature and has to be created by bombarding U238 nucleli with neurtons. Its development had nothing to do with the atmmic bomb project. Its creation was was an acto pure science. Uranium is the heaviest naturally occuting ekement--at least in any quantity. It completed Mendelev's periodic table. Nuclear pgysicists, however, wanted yo know if heavier elements could be created and what they were like. Scientistas at the University of California, Berkeley addressed this issue. A group led by Dr. Glenn T. Seaborg first produced and isolated plutonium (December 14, 1940). Usuing the University cyclotron they subjected U238 with deuteron bombardment. By the time they suceeded, war time secrecy regulations were in place and required them to keep their success secret. It was in fact one of the great secets of the War, if not the gretest. U238 was not fissile and thus the major problem in building the bomb was enriching uranium to separate out fissile U235. This was an enormous undertaking because U-235 was only about 1 percent of natural uranium. Thus the enrichment process was a huge undertaking requiring banks of cyclotrons and enormous quqntities of energy. Both the German abd Jao]panese atomic projects failed primarily bcause they did not know about plutonium. Seaborg's Berkly group first synthesized Neptunium-238 (half-life 2.1 days). It quickly beta-decayed to form a new heavier element with atomic number 94 and an atomic weight 238 and a more stable half-life (87.7 years). The Seaborg group decided to call it plitonium (after Pluto the then mext planet after Uranus and Naptune). Plutonium prived to be the heaviest primordial element because of its nuclear stability. PU244 is virtually indestructable, at least in human terms (half-life of 80 million years). Because of its stability, trace qualtities have been found in nature. Its imprtance is that while only 1 percent of natural uranium is the fissile U235 isotope, the 99 percent of U238 could be used to produce fissile plutonium isotopes, both PU239 and PU 241 are fissile. If the Japanese or Germans had known this they would have had a real chance of building a bomb. One reason that the Japanese and German scientists were so surprised about the America bomb at the end of the War is that they knew how difficult it was to enrich uranium. PU240 was a different matter entirely. PU240 was even more dangerous that the other isotopes. PU240 exhibits a high degree of spontaneous fission, not what bomb makers want to work. PU240 thus raised the neutron flux of any material produced. Thus the presence of PU240 severely damaged the usability of the plutonium being prpduced for weapons or y as reactors. The percentage of PU240 thus determines its nuclear grade (weapons-grade, fuel-grade, or reactor-grade). Plutonium isotopes are expensive and difficult to separate, so it was a major problem that had to be solved by the Mabhattan Projdct, but it enabled the vast untities of U236 which were otherwise useless to be used to produce weapons. The Trinity test at Almomzgordo was a plutonium weapon.

The Bomb

Groves chose Los Alamos, New Mexico as a location to actually develop and assemble the bomb or "gadget" a it was called. This isolated town had by March 1943 been turned into a high-technology boomtown. The technical difficulty associated with building the bomb were enormous. By early 1945 (February and March) the Los Alamos scientific team had assembled both U-235 and Plutonium bombs. The Y-12 Plant at Oak Ridge provided the bomb-grade U-235 used for the Little Boy bomb. The Harford plant provided the Plutonium used for the Trinity Test and the Fat Man bomb. Oppenheimer and his group were confodent the uranium bomb would work. They were less sure about the plutonium bomb.


The Manhattan Project was the greatest American secret of World War II. Even Vice President Truman was not told about it, until President Roosevelt died. Ironically Stalin knew about it before Truman was informed.

Soviet Atomic Bomb Project

The Soviet Union was no giving any significant attention to nuclear physics befor the advent of World War II. Soviet researchers were focused on more practical, industrial areas. Researchers during the Greatv Purges did not want to explore innovative ideas leastv they be accused of easteing sdtate resources. There was also the danger of Lysenkoism which severly damaged early Soviet science. Thus Soviet physicists, influenced by Abram Ioffe, attempted to emphasize research designed to strengthen the Soviet economy and industry. They intentionally avoided research projects that would be susprtable being criticized as "theoretical" and "impractical". And this was how nuclear physics was perceived. The German discovery of nuclear fission (1939) caused enormous interest in world-wide scientific community, including Soviet scientists. The theoretical possibility of a nuclear weapon was immediately apparent. Nuclear scientists did not think it was a practical development in the forseeable future. Yakov Frenkel did the first theoretical Soviet work on fission (1940). Georgii Flerov and Lev Rusinov reached important conclusins about a nuclear chain reaction. The German invasion (June 1941) caused the entire Soviet industrial and research establishment to be devoted to the immediate task f defeating the Germans. Any major activity in the Soviet Union required Stalin's approval. Stalin was first informed of American nuclear research by Georgii Flerov (April 1942). Flerov noted that physics journals in American, Britain, and Germany were no longer publising paopers on nuclear fission. And leading physicists were no longer publishing anything. The reasons were obvious. lerov urged Stalin to immediately launch a Soviet nuclear program. The massive effort needed to fight the Germans on te Eastern Front, however, that resources were not available for any substantial effort. Stalin did assign Foreign Minister Vyacheslav Molotov to begin a program. Molotov was replaced by NKVD head Lavrentii Beria (1944). The scientific head of the project was the nuclear physicist Igor Kurchatov. Other researchers Yuli Khariton, Yakov Zeldovich and Andrei Sakharov who would later become the lead theoretical designer of the hydrogen bomb ans subsequently a major disident. While resources were at first limited, the NKVD was able to provide a great deal of information about the Manhattan Projct.

Soviet Penetration

Widely publicized spy cases during the Cold war added to the American public concern about an internal Communist threat. Two of the most important involved involving Alger Hiss and Julius and Ethel Rosenberg. At the time the degree to which the Soviets had penetrated the Manhattan Project was not known. Only later were the Verona Intercepts lead to a fuller understanding of the Soviet spy network. Later Robert Oppenheimer himself came under suspicion. The Rosenbergs were not the most harmful spies. There were others, including Klaus Fuchs who provided much more useful information. There is no doubt, however, Julius Rosenberg was a Soviet spy and was guilty of passing atomic secrets to the Soviets. While the Rosenbergs provided information of only limited value, they proved to be enormously effective in Soviet propaganda to condemn the United States. Rudolf Abel was the Soviet master spy in America during the Cold War. He operated under the name of William Fischer. He entered the United States in 1948 and set up an effective ring of agents. His primary assignment was nuclear weapons. He worked with both the Cohens and the Rosenbergs.

German Spies (November-December 1944)

The Abwehr was also cocerned over reports that the Americans were working on atomic energy. Apparently there was no immediate concern that the Anmerican could develop an atmoci bomb. NAZI attitudes on such mtters were if they were incapable of building a bomb, surely the Americans could not do it. Atomic energy was a achievable goal. The Abwehr thus decided to dispatch two agents to find out just what the Americans were doing (summer 1944). They must have been concerned as because by mid-1944, Allied armies were closing in on the Reich and thus there wre many much more immediate concerns. The Germans during the War dispatched 46 agents, all were arrested by the FBI very quickly and 6 were executed. The NAZI atmnic spies were the last two. The mission was led by Eric Gimple, a German spy who woked in Peru reporting on merchant shipping. The FBI convinced the Peruvian Government to deport him. He then worked on several missions for the Abwehr including one attempt tp deliver Stuka aircraft by submarine to within striking range of the Panama Canal. His companion was William Colepaugh an American traitor. Colepaugh's granparents had instilled a love of the Fatherland in him. He had flunked out of MIT and had then dismissed from the Navy because of his pro-NAZI orientation. (America during World War II was not affected by the political correctness that allowed Major Hassan to murder 13 Americans in 2009.) Copaw joined the merchant marine and then jumped ship in Lisbon and thus was able to reach Germany. His job was to assist Gimble with the language and fitting into the American landscape. The U-1240 delivered the two with $60,000 in cash and $150,000 in diamonds to Frenchmen's Bay, Maine (November 29). The effort was named Operation Magpie. Ginble was surprised to find that there were no police controls at the train stations. They headed for New York. They were given only one contact. They managed to learn almost nothing. Unlike the Soviets, there were no sympathizers within the Manhattan Project. Gimble learned that reseach was underway at severalmlocations. MIT was working on heavy water. Uranium was being imported from Canada. Other places were wrking on graphite. They leaned nothing about research on a bomb, let along that one was being built. They purchased radio parts and built a transmitter. One report was transmitted. Colepaugh with the NAZI-supplied cash was soon enjoying himself in New York and he was having second thoughts aboutv the Fatherland, perhaps reading the newspapers about Allied advances. He decided to abandon Gimple and took off with the cash and diamonds. Gimble managed to recover them in Grand Central Station. Colepaugh decided to turn himself into the FBI and helped them cash Gimble. The FBI arrested Gimble at a newstand buying South American newspapers (December 30). American interogators attempted to turn him, but he refused to work against Germany. They were both tried at Fort Jay and found guilty of espionge. President Roossevelt's death and Germany's surrender saved them from execution. [Gimble]

Interim Committee (May 1945)

We do not know if President Roosevelt calculated the use of the atomic bomb are how sure he was that the huge investment in resources would come to fruition. We do know that he took no steps to etablish a body to assess the use of the bomb. This was let to President Truman who was not informed about the bomb before President Roosevelt died. He ordered the creation of what became known as the Interim Committee to advise him. The Interim Committee was a secret high-level group established (May 1945). It was chaired by United States Secretary of War, Henry L. Stimson, at the urging of top figures in the Manhattan Project and with the approval of President Truman. Its task was to advise the President on issues associated with nuclear energy which at the timemeant the atomic bomb which was nearing completion. The scientist at Los Almos had not doubtthat thecuranium bomb would work. They had not doubts about the plutonium bomb. The Interim Committee was made up of key political, scientific and industrial figures. The Committee had broad terms of reference which included advising the President on wartime controls and the release of information. It was also given instructions to consider post-war controls and policies related to nuclear energy, including needed legislation. Its first and most obvious assignment was to advise on the manner in which nuclear weapons should be employed against Japan. With VE-Day (May 7), Japan was the inly remaining Axis country and was still resiting despite decisive defeats in the Pacific war and the destriction of it cities by conventional bombing. The term 'Interim' was used because it was anticipated a permanent body would be installed after the War. The permanent body would be the Atomic Energy Commission (1946). The first meeting was held (May 9). The Committee very quickly reached a consensus (June 1). The meeting log read, "Mr. Byrnes [Secretary of State] recommended, and the Committee agreed, that the Secretary of War should be advised that, while recognizing that the final selection of the target was essentially a military decision, the present view of the Committee was that the bomb should be used against Japan as soon as possible; that it be used on a war plant surrounded by workers’ homes; and that it be used without prior warning." ["Notes of the meeting", pp. 8-9.] There was only one disenting vote.

Targetting Committeee (late-April 1945)

The United States did not begin to consider the actual targets for the atomic bombs that were were nearing completion until the NAZI regime was nearing collapse. The Targeting Committee (TC) first met (late-April). Within days Hitler had shot himself and the Red Army complete is conquest of Berlin. The Committee was presented with a Priority List by the Twenty-first Bomber Command (21BC). The Command was a unit of the Twentieth Air Force in the Mariana Islands and was conducting the strategic bombing campaign against the Japanese Home Islands. As a result, the Targeting Committee never received a list of German targets. As far as we know, note was never prepared by the Eighth Air Force in Europe. Hiroshima was not high on the 21BC priority list, in part because the planning for invasion of the Home Islands was just beginning. The TC held its second committee at Los Alamos (May 10-11). Five cities were seen as a priority, and Hiroshima had risen in importance. Dr. Stearns at Los Alamos described his work on target selection. He had used three criteria: "(1) they be important targets in a large urban area of more than three miles in diameter, (2) they be capable of being damaged effectively by a blast, and (3) they are unlikely to be attacked by next August." ["Minutes of the Second meeting..."] Dr. Stearns had a list of five targets which the Air Force would be willing to reserve for our use unless unforeseen circumstances arise." The targets on his list were Kyoto, Hiroshima, Yokohama, Kokura Arsenal, and Niigata. Kyoto and Hiroshima were given the highest priority. The meeting log noted, "The possibility of bombing the Emperor’s palace was discussed. It was agreed that we should not recommend it but that any action for this bombing should come from authorities on military policy. It was agreed that we should obtain information from which we could determine the effectiveness of our weapon against this target.

Trinity Test (July 1945)

There was no way of knowing if the atmic bomb worked until it vwasctested. This was the first atmoic bomb and scientists varied about just what result from a nuclear explosion. Even at Los Alamos there were serious doubts that it would work. The most serious problem in building a uranium bomb was producing weapons-grade uranium. As there was only enough uranium for one bomb and Openhimer and his colleagues had considerable confidence in the gun-type design, the Until the atomic bomb could be tested, doubt would remain about its effectiveness. The world had never seen a nuclear explosion before, and estimates varied widely on how much energy would be released. Some scientists at Los Alamos continued privately to have doubts that it would work at all. There was only enough weapons-grade uranium available for one bomb and confidence in the gun-type design was high, the researchers began to ship the uranium bomb ("Little Boy") to the Marianas without testing it (July 14, 1945). In contrast, several plutonium bombs were "in the pipeline" and would be available in a matter of weeks and months. Researchers had less confidence in the plutonium devices and it was thus decided to test one of the plutonium bomb. The first atomic bomb was tested at Trinity Site near Alamogordo (July 16, 1945). Trinity Site was named after a poem by John Dunn describing how God destroys to renew.

Use of the Bomb (August 1945)

The United States dropped two atomic bombs, the first on Hiroshima and the second on Nagasaki (August 6 and 9, 1945). The results were horendous. Japanese scientists were at the time working on an atmic bomb. This was of course secret and only a small number of officvials and ciebtisdts were aware of the work. Thus the Japanese were totally unprepared and had no idea a first what had ocurred. Military autorities assured the Emperor after the Hiroshima attack that the Americans could not possibly have produced enough uranium for a second bomb. War Minister Korechika Anami still wanted to continue the War, When told about the nushroom cloud, he replied, "Would it not be wondrous for this whole nation to be destroyed by a beautiful flower?" [Pellegrino] Most Americans believe it was the atmnic bomb that forced the Japanese to surrender. It surely was a factor, but even before the two attacks, coventional attacks had destroyed mny Japanese cites. It is likely that the decesion to surrender was also infuenced indicrectly through Moscow. The Hiroshima attack caused Stalin to order the immediate declaration of war on Japan and invasion of Manchuria least Japan surrender before the Soviets attacked. The prospect of a Soviet occupation was a major factor in the Emperor's decesion and the Army's acquiesence to the Emperor's decession. The human tragedies are heart rending. There are many factual accounts. Many fiction writers have also addressed the cataclism. One particularly moving fction account was about Emikio Amai age 6. "One morning toward the end of the summer they burned away by face. My little brother and I were playing on the bank of the river." [Bock] At the time there was no real controversy in America about President Truman's decesion to use the bomb. Over time the American use of the bomb has become controversial even in America. The Japanese largely because of the bomb see thenselves as a cictim of the War. Japanese authors write a great deal about the atmic bomb and very little about the much larger number of people that died at their heands throughout SoutheastvAsia nd the Pacific. While many of the issues concerning the bomb can be debted, One more definitive observation is that the atmic bomb was not just one more weapon, albit of great power, Dropping the bomb represented one of the fundamental inflection point in history. [Pellegrino]

Production Capacity

The United States dropped the only two bombs it had (August 6 and 9, 1945). They were dropped in short succssion to give the Japanese the impression that there was a stockpile of bomns ready to be dropped. But there was no such stockpile. The day after the Nagasaki bomb was dropped, Maj. Gen Groves informed the War Department that another plutonium bomb could ve 'ready for delivery on the first suitable weather after 17 or 18 August." [Neufeld] This suggests that the United States had the capability of building about one bomb about every week. The United States was not sure how the Japanese would react. Thus planners were prepared to build at least 12 bombs.

Actual Production

One might have expected that the United States after the Japanese surrender would have built a number of the bombs fo national defense and maintained the World War II production facilities for bomb production. This did not occur. Substantial bomb production did not begin until after the Soviet exploded their first bomb (1949). This and the rising Cold War tensions resulted in a bomb building initiative.

The Cold War

The United States developed nuclear weapons during World War II. It was a massive research anf development effort--the Manhattan Project. The Germans were unable to penetrate the security around thge Project, but the Soviets did. The Goldbergs were just one of the active Soviet spy rings. The first American atomic bomb was a uranium (fission) sucessfully andcsuccessfully tested (July 1945). A month latter, uranium and plutonium boms were used to end the Pacific War. The United states for a brief period had a monopoly on atomic weapons. American planners assumed that monoply would last some time. The Soviets had, however, their own nuclear experts and had begun their atomic project during the War. Stalin ordered the project after Soviet spies began reporting on the American project. The Soviet research was directed by nuclear physicist Igor Kurchatov. The Soviets aided by their spy operations and captured German scientists, exploded their first atomic bomb (August 1949). It was no accident that within a year, the North Korans heavily armed with Soviet weapons launched the Korean War. America debated the H-bomb (fussion weapon). Oppehimer argued against it, but his loyalty was questioned. Teller argued for it. Unbeknownst to the Americans, the Soviets had already begun their H-bomb program. [Reed and Stillman] Stalin put NKVD Chief Beria in charge of the project. They weapons were exponentially more powerful than fission weapons. The Soviets tested a primitive fusion weapon (1953). The American H-bomb was the first true fusion weapon and was exploded over Bikini (1954). The Soviets followed with their own H-bomb (1955). Andrei Sakharov played a major role. The Soviets set out to build a super bomb. Nuclear fallout from some of the mega-bombs they exploded, however, caused the Soviet leadership to respond to American overtures for limits on nuclear testing. The first step was banning tests in the atmoshere. The Limited Test Ban Treaty (1963) banned all nuclear tests except for those performed underground. From then until the signing of the Comprehensive Test Ban Treaty (1996), most nuclear tests were performed underground. The Chinese exploded their first nuclear weapon (1964) and their first H-bomb 3 years later (1967). Nuclear weapons are no longer a Cold war Issue. With the end of the Cold war, the United States and Russia have reduced their nuclear arsenal. The arms race in South Asia between India and Pakistan has gone nuclear and both countries now have large niuclear arsenals. Israel is widely believed to possess nuclear weapons. North Korean has also developed nuclear weapons. And now Iran is on the verge of developing nuclear weapons.


Black, Conrad. Franklin Roosevelt: Champion of Freedom (Public Affairs: New York, 2003), 1280p.

Corwell, John. Hitler's Scientists: Science, War, and the Devil's Pact (Viking, 2004), 535p.

Gimbel, Eric. Spy for Germany.

Goudsmit, Samuel. ALSOS (1947).

Klotz, Irving M. "Captives of Their Fantasies: The German Atomic Bomb Scientists" Chem. Educ. 1997 74 204.

Morgan, Ted. FDR: A Biography (Simon & Schuster: New York, 1985), 830p.

Neufeld, Michael. Senior Curator. National Air and Space Museum. "Ask Smithsonian," Smithsonian Magazine (July/August 2016), p. 136

Overy, Richard. Why the Allies Won.

Pais, Abraham. Niels Bohr's Times, in Physics, Philosophy and Polity (Oxford University Press, 1991).

Pellegrino, Charles. The Last Train from Hiroshima: The Survivors Look Back (Henry Holt, 2010). 367p.

Powers, Thomas. Heisenberg's War (Knopf, 1993).

Rhodes, Richard. The Making Of The Atomic Bomb.

Schwartz, David N. The Last Man Who Knew Everything: The Life and Times of Enrico Fermi, Father of the Nuclear Age (2017).

Walker, Mark. "The German Atomic Bomb" from "Heisenberg, Goudsmit and the German Atomic Bomb," Physics Today (January 1990).

"Notes of meeting of the Interim Committee , June 1, 1945". The Harry S Truman Library and Museum.

"Minutes of the second meeting of the Target Committee Los Alamos, May 10-11, 1945," U.S. National Archives, Record Group 77, Records of the Office of the Chief of Engineers, Manhattan Engineer District, TS Manhattan Project File '42-'46, folder 5D Selection of Targets, 2 Notes on Target Committee Meetings.


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Created: May 16, 2003
Spell checked: 10:52 PM 9/22/2008
Last updated: 8:56 AM 9/2/2016