The Manhattan Project Decision
How FDR launched the most secret and consequential weapons program in history, transforming a scientific warning letter into the atomic age.
Einstein's Letter
On August 2, 1939, Albert Einstein signed a letter to President Roosevelt warning that recent research in nuclear physics made it conceivable that 'extremely powerful bombs of a new type may be constructed,' and that Germany might be pursuing this technology. The letter, largely drafted by physicist Leo Szilard, recommended that the US government establish a systematic relationship with nuclear researchers and secure uranium supplies.
Roosevelt's response was characteristically pragmatic. He appointed an Advisory Committee on Uranium, but initial progress was slow. It was not until the MAUD Committee report from Britain in 1941 — which concluded that an atomic bomb was both feasible and could be built in time to affect the war — that the American effort accelerated dramatically. In December 1941, just days before Pearl Harbor, Roosevelt formally authorized what would become the Manhattan Project.
The scale of Roosevelt's commitment was staggering. The Manhattan Project eventually employed over 125,000 people and cost nearly $2 billion (approximately $30 billion today). It was managed by the Army Corps of Engineers under General Leslie Groves, with scientific leadership provided by J. Robert Oppenheimer at the Los Alamos laboratory in New Mexico. The secrecy was so complete that Vice President Truman did not learn of the project's existence until after Roosevelt's death.