The order to attack Japanese cities with atomic bombs was issued on July 25, 1945, by acting U.S. Army Chief of Staff Thomas Handy to Gen. Carl Spaatz, commander of the U.S. Strategic Air Forces, to "deliver (the) first special bomb as soon as weather will permit after about Aug. 3, 1945. ... The target list: 'Hiroshima, Kokura, Niigata and Nagasaki.' "
Further attacks on the above targets were authorized to proceed as soon as additional atomic bombs were delivered. The order explicitly confirmed that Chief of Staff George Marshall and Secretary of War Henry Stimson had approved it. U.S. President Harry Truman, of course, provided the ultimate authorization for dropping the bombs.
Before the above order to attack was given, the U.S. Air Force had started practicing to use the atomic bombs from around mid-July through early August in Japan, dropping 49 mock bombs with conventional explosives, each weighing 6.5 tons, the same as the one used on Nagasaki, on 18 prefectures. The training was to learn the necessary trajectory for the real thing.
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