Timeline of The Manhattan Project - 1945

1945

• January: Brigadier General Thomas Farrell is named Groves' deputy.
• January 7: First RaLa test using exploding bridgewire detonators.
• January 20: First stages of K-25 are charged with uranium hexafluoride gas.
• February 2: First Hanford plutonium arrives at Los Alamos.
• April 22: Alsos Mission captures German experimental nuclear reactor at Haigerloch.
• April 27: First meeting of the Target Committee.
• May 7: Nazi Germany formally surrenders to Allied powers, marking the end of World War II in Europe; 100-ton test explosion at Alamogordo, New Mexico..
• May 10: Second meeting of the Target Committee, at Los Alamos.
• May 28: Third meeting which works to finalize the list of cities on which atomic bombs may be dropped: Kokura, Hiroshima, Niigata and Kyoto.
• May 30: Stimson drops Kyoto from the target list.
• June 11: Metallurgical Laboratory scientists under James Franck issue the Franck Report arguing for a demonstration of the bomb before using it against civilian targets.
• July 16: the first nuclear explosion, the Trinity nuclear test of an implosion-style plutonium-based nuclear weapon known as the gadget at Alamogordo; USS Indianapolis sails for Tinian with nuclear components on board.
• July 19: Oppenheimer recommends to Groves that gun-type design be abandoned and the uranium-235 used to make composite cores.
• July 24: President Harry S. Truman discloses to Soviet leader Joseph Stalin that the United States has atomic weapons. Stalin feigns little surprise; he already knows this through espionage.
• July 25: General Carl Spaatz is ordered to bomb one of the targets: Hiroshima, Kokura, Niigata or Nagasaki as soon as weather permitted, some time after August 3.
• July 26: Potsdam Ultimatum is issued, threatening Japan with "prompt and utter destruction".
• August 6: B-29 Enola Gay drops Little Boy, a gun-type uranium-235 weapon, on the city of Hiroshima, the primary target.
• August 9: B-29 Bockscar drops a Fat Man implosion-type plutonium weapon on the city of Nagasaki, the secondary target, as the primary, Kokura, is obscured by cloud and smoke.
• August 12: The Smyth Report is released to the public, giving the first technical history of the development of the first atomic bombs.
• August 14: Surrender of Japan to the Allied powers.
• August 21: Harry K. Daghlian, Jr., a physicist, receives a fatal dose (510 rems) of radiation from a criticality accident when he accidentally dropped a tungsten carbide brick onto a plutonium bomb core. He dies on September 15.
• September 4: Manhattan District orders shutdown of S-50 liquid thermal diffusion plant and the Y-12 Alpha plant.
• September 8: Manhattan Project survey group under Farrell arrives in Nagasaki.
• September 17: Survey group under Colonel Stafford L. Warren arrives in Nagasaki.
• September 22: Last Y-12 alpha track ceases operating.
• October 16: Oppenheimer resigns as director of Los Alamos, and is succeeded by Norris Bradbury the next day.