Second Sino-Japanese War. On 6 and 9 August , the United States detonated two atomic bombs over the Japanese cities of Hiroshima and Nagasaki , respectively. The bombings killed between , and , people, most of whom were civilians, and they remain the only use of nuclear weapons in an armed conflict.
Japan surrendered to the Allies on 15 August, six days after the bombing of Nagasaki and the Soviet Union's declaration of war against Japan and invasion of Japanese-occupied Manchuria.
The Japanese government signed the instrument of surrender on 2 September, effectively ending the war. This undertaking was preceded by a conventional bombing and firebombing campaign that devastated 64 Japanese cities, including an operation on Tokyo. The war in the European theatre concluded when Germany surrendered on 8 May , and the Allies turned their full attention to the Pacific War. By July , the Allies' Manhattan Project had produced two types of atomic bombs: " Little Boy ", an enriched uranium gun-type fission weapon , and " Fat Man ", a plutonium implosion-type nuclear weapon.
The Allies called for the unconditional surrender of the Imperial Japanese armed forces in the Potsdam Declaration on 26 July , the alternative being "prompt and utter destruction".
The Japanese government ignored the ultimatum. The consent of the United Kingdom was obtained for the bombing, as was required by the Quebec Agreement , and orders were issued on 25 July by General Thomas T. Handy , the acting chief of staff of the United States Army , for atomic bombs to be used against Hiroshima, Kokura , Niigata , and Nagasaki. These targets were chosen because they were large urban areas that also held militarily significant facilities.
