S-1 Executive Committee

The S-1 Executive Committee laid the groundwork for the Manhattan Project by initiating and coordinating the early research efforts in the United States, and liaising with the Tube Alloys Project in Britain.

In the wake of the discovery of nuclear fission in December 1938, the possibility that Nazi Germany might develop nuclear weapons prompted Leo Szilard and Eugene Wigner to draft the Einstein–Szilárd letter to the President of the United States, Franklin D. Roosevelt, in August 1939. In response, the Advisory Committee on Uranium was created at the National Bureau of Standards under the chairmanship of Lyman J. Briggs to determine the feasibility of nuclear weapons. In June 1940, the National Defense Research Committee (NDRC) was created to coordinate defense-related research, and the Advisory Committee on Uranium became the Uranium Committee of the NDRC. In June 1941, Roosevelt created the Office of Scientific Research and Development under the leadership of Vannevar Bush (OSRD), at it incorporated the NDRC, now under James B. Conant. The Uranium Committee became the Uranium Section of the OSRD, which was soon renamed the S-1 Section for security reasons. By May 1942, it was felt that the S-1 Section had become too unwieldy, and in June 1942, was replaced by the smaller S-1 Executive Committee.

The feasibility of nuclear weapons was demonstrated by the British MAUD Committee, and its results were shared with the Advisory Committee on Uranium by the Tizard Mission. The S-1 Section coordinated research into nuclear weapons in United States, in cooperation with the British Tube Alloys project. The United States Army created the Manhattan District in June 1942, and took over responsibility for the development of nuclear weapons from the S-1 Executive Committee in September 1942. The OSRD's research and development contracts were terminated as they lapsed, and production contracts were terminated and transferred to the Army. Although the S-1 Executive Committee remained as an advisory body, it became inactive. The OSRD and NDRC continued to influence the Manhattan Project through the participation of Bush and Conant in the Military Policy Committee that controlled what became the Manhattan Project.