In the summer of 1939, a group of physicists, including several who had fled Hitler’s Germany, met to discuss their fears of Germany developing a uranium-based weapon. It was decided that the best course of action was to inform President Roosevelt immediately of their concerns.
Because Albert Einstein had a previous personal relationship with the Roosevelts and was internationally well-known for his expertise, a letter informing the President about the dangers of a nuclear chain reaction bomb was drafted for Einstein’s signature.
This August 2, 1939 letter was personally delivered to the President on October 11, 1939 (the outbreak of the war intervened) by Alexander Sachs, a longtime economic adviser to FDR. After learning of the letter’s contents, President Roosevelt told his military adviser General Edwin M. Watson, “This requires action.” The action FDR required would evolve into the Manhattan Project.