The Manhattan Project: Making the Atomic Bomb

Bush Reports to Roosevelt

Without waiting for Compton's committee to finish its work, Bush went to see the President. On October 9 Bush met with Roosevelt and Vice President Henry A. Wallace (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." ¹⁹

Compton reported back on November 6, just one month and a day before the Japanese attack on Pearl Harbor on December 7, 1941, brought the United States into World War II (Germany and Italy declared war on the United States three days later). Compton's committee concluded that a critical mass of between two 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" ²⁰

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