Nagasaki was struck by the second atomic bomb used against Japan in August 1945.
The United States dropped the uranium bomb Little Boy on Hiroshima on 6 August. Three days later, on 9 August, a B-29 bomber released the plutonium bomb Fat Man over Nagasaki. The second mission was originally directed toward Kokura, but cloud and smoke obscured the aiming point, so the aircraft proceeded to its secondary target, Nagasaki.
Nagasaki’s bombing occurred on the same day that the Soviet Union entered the war against Japan and invaded Manchuria. Japanese leaders were therefore confronting both the atomic attacks and a major Soviet offensive. The relationship among these events remains a major subject in historical discussions of Japan’s decision to surrender.
Japan announced acceptance of the Allied terms on 15 August, and the formal surrender document was signed on 2 September. The bombing date should not be mistaken for either of those surrender dates.