• The National WWII Museum Blog
dividing bar

FDR Approves Building an Atomic Bomb: 70th Anniversary October 9, 1941

dividing bar

On October 9, 1941, one of the most important, lonely and secret decisions in the course of the Second World War was made by President Franklin D. Roosevelt. In a small meeting with only Vice President Henry Wallace and the head of the National Defense Research Committee Vannevar Bush present, Roosevelt committed the United States government to embark upon a program of intensified research into the feasibility of a fission bomb. The major questions of how much money, construction projects, personnel, and administrative structures needed to build an atomic bomb were not decided at this meeting. In Vannevar Bush, Roosevelt was giving the green light to a man he trusted to develop those frameworks as needed, and Roosevelt was aware that Bush would use Presidential authority to aggressively push the project forward. The United States was still technically a neutral nation in October 1941, yet Roosevelt became the first national leader to commit his nation to the effort to achieve a nuclear device. In so doing, he also decisively changed the nature of the relationship between American government and American science, a cultural change that has persisted to the present day.

Once begun down this pathway, the Americans would be the first to successfully detonate a nuclear bomb with the Trinity test in the desert of New Mexico on July 16, 1945. But there was nothing inevitable in the story of what would be officially christened as the Manhattan Project in August, 1942. Before the culmination of the technical project, however, Roosevelt’s decision established important political parameters for the future of the nation and the world long after the end of the war. He did not wish to consult on nuclear issues with the American Congress which voiced the democratic concerns of the public, the military forces which would use the weaponry, or the scientists who developed and implemented the technology. He did not wish to develop the technology in an international effort with the Allies (although it will be seen that Great Britain made a deep contribution to Roosevelt’s decision to pursue the project in October 1941). Almost instinctively, Franklin Roosevelt reserved all major policy aspects of the atomic bomb to himself and the American presidency.

When the Second World War commenced in Europe in 1939, physicists across the world recognized that the discovery of nuclear fission had theoretically made possible the building of atomic bombs. Intellectual recognition of a possibility by scientists was one thing; having the developed physics community, financial resources, industrial capacities, technological prowess, and political will to actually build an atomic bomb was an entirely different proposition. In many countries, there existed unique social arrangements for the promotion of science. In France, government sponsorship was most prominent; in Great Britain, the universities were the main supporters. In the United States, private foundations and philanthropy were the key promotional institutions of the sciences through elite university programs. Government was not highly involved in scientific research or financial sponsorship.

With the discovery of nuclear fission, physicists saw two potential pathways to creating a bomb out of uranium. The first involved separating out the light isotope U-235; the second involved the transformation of U-238 through neutron bombardment to create plutonium. In each case, there were scientific issues of securing enough of raw materials, quality refinements, and suitable amounts of the fissionable material. In terms building a bomb, plants and nuclear reactors would have to be designed, constructed, and operated to produce the necessary elements, and then effective detonation devices would also have to be designed, constructed, tested and operated. The undertaking of a bomb project was a massive commitment and allocation for a nation-state, particularly in a time of war and competing demands and resources allocations.

In February 1940, two refugee scientists in Great Britain, Otto Frisch and Rudolph Peierls, essentially worked out the theoretical operation of a uranium fission bomb. They sent a memorandum of their findings to the Committee on the Scientific Survey of Air Defense, the most important committee of the British government charged with using science for war efforts. Recognizing the supreme importance of the issue, the British government immediately sought to protect itself and keep the memorandum secret by sending the memorandum to a select committee of top British scientists. For over a year, the best minds in British science on the dourly codenamed Maud Committee examined and tested the Frisch-Peierls theoretical model of an atomic bomb, and concluded that their conceptual method would work as a practical weapon. In early September 1941, the British government had decided to go forward with fast-tracked research and development, and if the results were promising, to then attempt building a bomb, preferably with plants located in North America, far away from Luftwaffe bombers. But the Maud committee had also previously decided in the spring to share their knowledge with the Americans in order to build and solidify their relationship. In spring 1941, Britain was fighting on alone and financially supported by American Lend-Lease aid. Any British decision to actually build a British bomb had to consider that Britain did not have the financial reserves, industrial plant, and distance from war needed for such a massive undertaking. Canada or America would have to be brought into any British effort to build the bomb; and only America truly had the necessary resources and conditions for such a project to succeed.

In terms of an American bomb project, the issue had first drawn the attention of President Franklin D. Roosevelt when Albert Einstein wrote the president a letter in August 1939 outlining his concerns that Germany might pursue such a weapon, and with it Hitler might become invincible. With Germany’s invasion of Poland and the outbreak of the European war in September 1939, the emissary selected to bring Einstein’s letter, the economist Alexander Sachs of Lehman Corporation, was unable to see Roosevelt until October 11, 1939. At the meeting, Roosevelt famously declared to his aide General Edwin “Pa” Watson, “This requires action,” but he then assigned study of the issue of a fission bomb to Lyman Briggs at the Bureau of Standards. Briggs was a trained scientist, but he had spent nearly forty years as a career government bureaucrat and was accustomed to worn ways of doing business. He was not familiar with the private world of foundations and philanthropy which had funded scientific research in America, and did not reach out to those institutions. He could not envision the new relationship which government would have to pioneer with the American scientific and technological community, and hence the atomic bomb project gained little momentum under the leadership of the Briggs Committee. The Briggs Committee had spent only $6,000 for the purchase of graphite needed to study fission. This is where matters stood in the late spring of 1940.

It was at this stage that other leadership began to emerge. The initial mover was Dr. Arthur Compton, a Nobel Laureate physicist for his work on cosmic rays. Compton knew that private interests would have to be engaged in any serious fission research (the Rockefeller Foundation had recently given a grant for over a million dollars for the cyclotron construction at the University of California laboratory run by Dr. Ernest Lawrence, an experimental physicist and fellow Nobel Laureate). Compton also recognized that progress and a realistic chance of success would have to be shown to engage the interest of the U.S. military, and hence gain deeper government support and commitment to the project. Aware of the scientific progress and fearful that Germany’s physics community might be working on the problem of building a bomb, Compton began to reach out to a small group of like-minded leaders in the American scientific community, including a man familiar with the scientific, technological, and Washington cultural worlds: Dr. Vannevar Bush.

Dr. Vannevar Bush and his Differential Analyzer in 1931

Vannevar Bush had received a joint doctoral degree in engineering from Harvard and the Massachusetts Institute of Technology in 1917. He then worked for the National Research Council, applying science to warfare, during the Great War. He joined the faculty at MIT, became a Dean and Vice President of engineering there, founded the industrial American Appliance Corporation (named Raytheon today), developed an analog computer, worked on defense contract work, and in 1939 accepted the presidency of the Carnegie Institute in Washington from which post he administered grants to promising scientific research. Bush took the lead on pushing the project. Through his persuasive powers and contacts with Roosevelt’s aid Harry Hopkins, he received an appointment with the President on June 12, 1940. His incisive and informed nature helped build trust between him and the President; Roosevelt liked that Bush was clear and concise in his analysis of the situation and direction that needed to be taken, and his serious and businesslike demeanor. Bush emerged from the meeting with Roosevelt with a new National Defense Research Committee, under which the Briggs Committee would pursue research, and organized with Bush himself installed as chairman.

Bush did not wish to establish government laboratories. Rather, his genius was at building networks and contracting with existing institutions (not individuals) for research, allowing for a flexibility of approach by government, and in which scale and complexity of research needs and construction could be calibrated. As an example to come, the laboratory eventually built at Los Alamos remains to this day a branch of the University of California. He stood out in his abilities compared to other scientific entrepreneurs in America, however, because of his unique understanding of the Washington DC political culture. He was an experienced and expert witness at Congressional and military hearings, and understood how to establish working relations with serious Washington players: generals, admirals, and Secretary of War Henry Stimson. Most importantly, Bush understood in 1940-41 that in a nation headed towards war, the best way to accomplish anything was by establishing and maintaining Presidential trust and executive authorization.

Still, even though the project now had a driven and competent political advocate and administrator, momentum and the ultimate outcome depended upon scientific progress. This was slow. For the scientists, the intellectual attempt to completely understand the fission process necessary to create a weapon was a daunting task when there was no fissionable material for experiments. The best scientific minds were still not directly involved or hired. In addition, as Hitler’s Luftwaffe and the Royal Air Force battled in the skies over the summer 1940, advancing radar was seen as the most immediate, pressing scientific need in the war. But in the winter of 1940, two events emerged from the University of California laboratory of Ernest Lawrence which engaged his interest deeply into an atomic project. First was the discovery by Glenn Seaborg of man-made plutonium; second, Lawrence realized his own cyclotron might become a processor for separating and accumulating U-235. Lawrence directly contacted Bush and began to urge a greater effort in building a bomb, but the situation was still unclear about whether such an effort was justified.

It was against this backdrop in the spring of 1941 that the British Maud Committee began sharing its results with American scientific consultants. That April Bush received reports from Kenneth Bainbridge, a young American physicist just returned from Britain who had been invited to sit in on Maud Committee meetings. This alerted Bush to lack of American progress under Briggs. He requested a review committee from the National Academy of Sciences to address his concerns with two focus points: could a bomb project succeed, and could it be done in time to affect the outcome of the war?

The National Academies review did not give Bush the clarifications he wished for. Although it did prophetically predict that an atomic bomb could be built by 1945, the two reports also ranked atomic bombs as third on the list of military priorities, and strongly urged more knowledge, but no course of action. Part of the reason the review did not produce Bush’s desired results appears to be a personal misunderstanding between the main players. The Nobel physicists Arthur Compton and Ernest Lawrence were the chairs of the National Academy review, but the engineer Bush and his closest colleague, President of Harvard James Bryant Conant (a chemistry Ph.D. very skeptical that a bomb could be made at this time), apparently were wary of the enthusiasm the physicists showed for their own field and knowledge. They felt that not enough engineering or chemical work had been done to flesh out the physical case. Bush was cautious. He did not want to inform President Roosevelt that a major effort and financial commitment should be made unless more convincing scientific evidence and consensus could be had.

But the Maud Committee continued to share its information with American scientists. In July, Bush was visited by Charles Lauritsen, an eminent American engineer and physicist at the California Institute of Technology, who was brought to London for consultation with the British government. Bush respected Lauritsen, who told Bush that the British thought a bomb could be built in two years, and he believed it. Shortly afterward, the Maud Committee forwarded their report to Bush through the London office of the NDRC. He found the report creditable. And in a final change, Bush’s closest colleague James B. Conant, previously a skeptic that a bomb was feasible, became a convert after a discussion with Harvard physical chemist George Kistiakowsky, who believed that a U-235 explosion was achievable. In science as in politics, the personal reputations, trust and judgment of other respected colleagues often supplies the final decisive element beyond the factual evidence.


Vannevar Bush and James Bryant Conant after the Trinity shot, Alamogordo, NM, July 16, 1945


By early September 1941, the Maud Committee was recommending that Britain build a bomb if possible, but also recognized that serious obstacles in money, technology, distance and war would hamper the British effort. The irony of the Maud Committee was that it did not persuade the British government to make a British bomb, but was instrumental in persuading the American government to follow this path. At that same time, Vannevar Bush was convinced that an atomic bomb could be built, and that the effort must be made for the war effort. He asked for an appointment to see President Franklin D. Roosevelt on October 9, 1941.

We have no document signed by Franklin Roosevelt from this meeting. The only documentation that exists is a memo from Vannevar Bush to James B. Conant. In it, Bush tells his colleague what was decided: that a vastly intensified research effort should be made, and that decisions on costs, construction, staffing and other issues would be decided by the President in the future. Bush would report to a six-man committee that would include the three men in the room, plus Conant as Bush’s deputy, and the civilian and military heads of the War department (Secretary of War Henry Stimson and General George Marshall). The committee never met; in reality, Bush reported directly to the President, who relegated nuclear policy as a sphere where only the political executive of the nation could make political and military decisions regarding the use of atomic weaponry. The looming war and the need for secrecy were also of paramount importance, and would have serious consequences in history. The decision to pursue a bomb, to build one in the quickest manner possible, had been taken, but these circumstances of war and secrecy would eliminate potential voices and policy alternatives when the bomb was ready four years later. By taking this step, in the future ever more powerful bombs could be built. But these issues lay in the future, to be dealt with there or unforeseen.

What was immediately unforeseen in October 1941 was whether the United States would be drawn into the Second World War. If the world situation continued to worsen (and by October 1941 with Hitler deep in Russia, astride Europe, Britain alone, and a menacing Japan many were pessimistic about the future) could the bomb project be halted? In the necessity to win the war, this possibility was remote. The United States was undertaking a task which once begun, could only be moved forward to an eventual completion. After meeting with the President on October 9, Vannevar Bush wasted no time: he immediately informed James B. Conant that he wanted new specific reports done on the critical mass and destructive effect of a U-235 bomb. The Japanese attack on Pearl Harbor on December 7, 1941, removed the last barriers on the project politically, as the United States joined the war. And the scientific progress that would be made on the atomic project would be so encouraging that when Bush next reported to Roosevelt in early 1942, the reality was that the President’s authorization for pushing on was a foregone conclusion.

President Franklin D. Roosevelt alone in his White House study

The Second World War was the indispensable historical framework that determined the manner of how the atomic bomb was created, especially the narrow window of events in 1939-1941. If either physical discoveries or political events had kept pace with each other in a different historical rhythm, it is unlikely that a bomb could have been built. In peacetime, scientists would have insisted upon the free exchange of knowledge with international colleagues and resisted the demands of secrecy which wartime national governments imposed. In peacetime, such a monumental industrial and financial commitment as the Manhattan Project could not be kept secret. In peacetime, there would be domestic political consequences for governments which pursued the bomb; there would international complications with other governments as well. The heavy encroaching storm clouds of war framed the decision faced by Roosevelt. The necessity of waging supreme war against an implacable Adolf Hitler provided the proactive reason to build the bomb. The lack of countervailing reasons meant there was no reason not to pursue the bomb. And in an atmosphere of wartime urgency and secrecy, there would be no domestic political opposition within. The decision made by President Franklin D. Roosevelt to pursue an atomic bomb on October 9, 1941, launched a great scientific journey, ushered in a transformed political and military world, and opened the door to the Nuclear Age we live in today.


Dr. Keith Huxen is the Senior Director of Research and History at the National World War II Museum.

dividing bar

2 Responses to “FDR Approves Building an Atomic Bomb: 70th Anniversary October 9, 1941”

julius eisenberg,md says:

my congratulations to dr.huxton for his admirable history of the
genesis of the atomic bomb.

truly,i read it with bated breath,as i might a novel(although i knew
the ending!(:-)).

i particularly appreciate the clarity of the reporting and who said what to whom.

previously, i had bits and pieces of unconnected information,as most
readers might:now i have a good sense of how all of this unfolded.

as a ww2 veteran and supporter of the museum,thank you.i would hope
it is widely available to our visitors.

Leave a Reply

  • (Your email address will not be published.)
dividing bar