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Organization and training
The 509th Composite Group was constituted on 9 December 1944, and activated on 17 December 1944, at Wendover Army Air Field, Utah, commanded by Colonel Paul W. Tibbets.[34] Tibbets was assigned to organize and command a combat group to develop the means of delivering an atomic weapon against targets in Germany and Japan. Because the flying squadrons of the group consisted of both bomber and transport aircraft, the group was designated as a "composite" rather than a "bombardment" unit. -
Preparations to invade Japan
Plans were underway for the largest operation of the Pacific War, Operation Downfall, the invasion of Japan, before the surrender of Nazi Germany on 8 May 1945.[7] The operation had two parts: Operations Olympic and Coronet. Set to begin in October 1945, Olympic involved a series of landings by the US Sixth Army intended to capture the southern third of the southernmost main Japanese island, Kyūshū.[8] Operation Olympic was to be followed in March 1946 by Operation Coronet, the capture of the Ka -
Choice of targets
General of the Army George Marshall, the Chief of Staff of the Army, asked Groves to nominate specific targets for bombing, subject to approval by himself and Secretary of War Henry L. Stimson. Groves formed a Target Committee in April 1945 chaired by himself, that included his deputy, Brigadier General Thomas Farrell; one of his staff, Major John A. Derry; Colonel William P. Fisher, Joyce C. Stearns and David M. Dennison from the USAAF; and scientists John von Neumann, Robert R. Wilson and Will -
Air raids on Japan
While the United States had developed plans for an air campaign against Japan prior to the Pacific War, the capture of Allied bases in the western Pacific in the first weeks of the conflict meant that this offensive did not begin until mid-1944 when the long-ranged Boeing B-29 Superfortress became ready for use in combat. Operation Matterhorn involved India-based B-29s staging through bases around Chengtu in China to make a series of raids on strategic targets in Japan between June 1944 and Janu -
Atomic bomb development
Working in collaboration with the United Kingdom and Canada, with their respective projects Tube Alloys and Chalk River Laboratories,[26][27] the Manhattan Project, under the direction of Major General Leslie Groves, of the U.S. Army Corps of Engineers, designed and built the first atomic bombs.[28] Preliminary research began in 1939, originally in fear that the Nazi atomic bomb project would develop atomic weapons first.[29] In May 1945, the defeat of Germany caused the focus to turn to use aga -
Potsdam ultimatum
On 26 July, Allied leaders issued the Potsdam Declaration outlining terms of surrender for Japan. It was presented as an ultimatum and stated that without a surrender, the Allies would attack Japan, resulting in "the inevitable and complete destruction of the Japanese armed forces and just as inevitably the utter devastation of the Japanese homeland". The atomic bomb was not mentioned in the communiqué. On 28 July Japanese papers reported that the declaration had been rejected by the Japanese go -
Leaflets
For several months, the US had dropped more than 63 million leaflets across Japan, warning civilians of air raids. Many Japanese cities suffered terrible damage from aerial bombings, some even 97% destruction. In general, the Japanese regarded the leaflet messages as truthful, however, anyone who was caught in possession of a leaflet was arrested by the Japanese government.[50] Leaflet texts were prepared by recent Japanese prisoners of war because they were thought to be the best choice "to app -
Hiroshima
At the time of its bombing, Hiroshima was a city of both industrial and military significance. A number of military camps were located nearby, including the headquarters of Field Marshal Shunroku Hata's 2nd General Army which commanded the defense of all southern Japan.[63] Field Marshal Hata's 2nd General Army was headquartered in the Hiroshima Castle and his command consisted of some 400,000 men, most of whom were on Kyushu where an Allied invasion was correctly expected.[64] Also present in H -
Post-attack casualties
According to the US Department of Energy, the immediate effects of the blast killed approximately 70,000 people in Hiroshima.[91] Estimates of total deaths by the end of 1945 from burns, radiation and related disease, the effects of which were aggravated by lack of medical resources, range from 90,000 to 166,000.[1][92] Some estimates state up to 200,000 had died by 1950, due to cancer and other long-term effects.[93] Another study states that from 1950 to 2000, 46% of leukemia deaths and 11% of
