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Ideas of New Weapon are Rised
Leó Szilárd and Eugene Wigner drafted the Einstein–Szilárd letter, which warned of the potential development of "extremely powerful bombs of a new type" -
First Concpets Designs For the Atom Bomb
Compton asked the theoretical physicist J. Robert Oppenheimer of the University of California, Berkeley, to take over research into fast neutron calculations—the key to calculations of critical mass and weapon detonation—from Gregory Breit, who had quit on 18 May 1942 because of concerns over lax operational security -
American and British Teamwork
The British and Americans exchanged nuclear information but did not initially combine their efforts. Britain rebuffed attempts by Bush and Conant in 1941 to strengthen cooperation with its own project, codenamed Tube Alloys -
First Meeting Held To Detirmine Feasiblity of Manhattan Project
The S-1 Committee held its first meeting on 18 December 1941 "pervaded by an atmosphere of enthusiasm and urgency" in the wake of the attack on Pearl Harbor and the subsequent United States declaration of war upon Japan and then on Germany -
Manhattan Project Starts
The Chief of Engineers, Major General Eugene Reybold, selected Colonel James C. Marshall to head the Army's part of the project in June 1942. Marshall created a liaison office in Washington, D.C., but established his temporary headquarters on the 18th floor of 270 Broadway in New York, where he could draw on administrative support from the Corps of Engineers' North Atlantic Division -
Bomb Weapon Design
Work on an alternative method of bomb design, known as implosion, had begun earlier at the instigation of the physicist Seth Neddermeyer. -
Weapon Design
In 1943, development efforts were directed to a gun-type fission weapon with plutonium called Thin Man -
Bombings of Japan
Little Boy explodes over Hiroshima, Japan, 6 August 1945
Fat Man explodes over Nagasaki, Japan, 9 August 1945 -
Manhattan Project Abolished
Military aspects were taken over by the Armed Forces Special Weapons Project (AFSWP).[296] Although the Manhattan Project ceased to exist on 31 December 1946, the Manhattan District would remain until it too was abolished on 15 August 1947