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President Franklin Roosevelt's note to Vannevar Bush giving Bush the tentative go-ahead to build the atomic bomb.A TENTATIVE DECISION TO BUILD THE BOMB
Washington, D.C.(1941-1942)
Events > Early Government Support, 1939-1942

Vannevar Bush moved swiftly to take advantage of the positive MAUD Report.  Without waiting for Arthur Compton's latest committee to finish its work confirming the MAUD Committee's conclusions, Bush on October 9, 1941, met with President Franklin D. Roosevelt and Vice President Henry A. Wallace (who had been briefed on uranium research in July).  Bush summarized the British findings, discussed cost and duration of a bomb project, and emphasized the uncertainty of the situation.  He also received the President's permission to explore construction needs with the Army.  Roosevelt instructed him to move as quickly as possible but not to go beyond research and development.  Bush, then, was to find out if a bomb could be built and at what cost but not to proceed to the production stage without further presidential authorization.  Roosevelt indicated that he could find a way to finance the project and asked Bush to draft a letter so that the British government could be approached "at the top.

Vannevar Bush and Arthur Compton, 1940Compton reported back on November 6, just a month and a day before the Japanese attack on Pearl Harbor on December 7, 1941, brought the United States into World War II. Compton’s committee concluded that a critical mass of between 2 and 100 kilograms of uranium-235 would produce a powerful fission bomb and that for $50-100 million isotope separation in sufficient quantities could be accomplished.  Although the Americans were less optimistic than the British, they confirmed the basic conclusions of the MAUD Committee and convinced Bush to forward their findings to Roosevelt under a cover letter on November 27.  Roosevelt did not respond until January 19, 1942; when he did, it was as commander-in-chief of a nation at war.  The President's handwritten note read, "V. B. OK -- returned -- I think you had best keep this in your own safe FDR" (above).   

S-1 Committee, Bohemian Grove, September 13, 1942.By the time Roosevelt responded, Bush had set the wheels in motion.  He put Eger V. Murphree, a chemical engineer with the Standard Oil Company, in charge of a group responsible for overseeing engineering studies and supervising pilot plant construction and any laboratory-scale investigations.   And he appointed Harold Urey, Ernest Lawrence, and Compton as program chiefs.  Urey headed up work including diffusion and centrifuge methods and heavy-water studies.  Lawrence took electromagnetic and plutonium responsibilities, and Compton ran fission chain reaction and weapon theory programs.  Bush's responsibility was to coordinate engineering and scientific efforts and make final decisions on recommendations for construction contracts.  In accordance with the instructions he received from Roosevelt, Bush removed all uranium work from the National Defense Research Committee.  From this point forward, broad policy decisions relating to uranium were primarily the responsibility of the Top Policy Group, composed of Bush, James Conant, Vice President Wallace, Secretary of War Henry L. Stimson, and Army Chief of Staff George C. Marshall.   A high-level conference convened by Wallace on December 16 put the seal of approval on these arrangements.  Two days later the S-1 Committee gave Lawrence $400,000 to continue his electromagnetic work.  

Werner Heisenberg, the leader of the German atomic bomb program.With the United States now at war and with the fear that the American bomb effort was behind Nazi Germany's, a sense of urgency permeated the federal government's science enterprise.  Even as Bush tried to fine-tune the organizational apparatus, new scientific information poured in from laboratories to be analyzed and incorporated into planning for the upcoming design and construction stage.  By spring 1942, as American naval forces slowed the Japanese advance in the Pacific with an April victory in the battle of the Coral Sea, the situation had changed from one of too little money and no deadlines to one of a clear goal, plenty of money, but too little time.  The race for the bomb was on.  

To view the next "event" of the Manhattan Project, proceed to "1942: Difficult Choices."


Sources and notes for this page.

The text for this page was adapted from, and portions were taken directly from the Department of Energy's Office of History and Heritage Resources publication: F. G. Gosling, The Manhattan Project: Making the Atomic Bomb (DOE/MA-0001; Washington: History Division, Department of Energy, January 1999), 9-10.  The quotations for this entry are from the History Office publication: Richard G. Hewlett and Oscar E. Anderson, Jr., The New World, 1939-1946: Volume I, A History of the United States Atomic Energy Commission (Washington: U.S. Atomic Energy Commission, 1972), 46, 48-49.  The photograph of Vannevar Bush and Arthur Compton is courtesy the Lawrence Berkeley National Laboratory.  The note from Roosevelt to Bush is available on the National Archives microfilm collection M1392, Bush-Conant File Relating to the Development of the Atomic Bomb, 1940-1945 (Washington: National Archives and Records Administration, 1990), reel #1/14.  Click here for more information on the photograph of the S-1 Uranium Committee.  The photograph of Werner Heisenberg is courtesy the National Archives; it is reprinted in Jeremy Bernstein, ed., Hitler's Uranium Club: The Secret Recordings at Farm Hall (Woodbury, NY: American Institute of Physics, 1996). 

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