Nagasaki was hit by the second atomic bomb used against Japan in 1945.
The United States dropped the plutonium implosion bomb known as Fat Man on Nagasaki on 9 August 1945. The bomber Bockscar released the weapon, which detonated over the Urakami Valley. The blast destroyed much of the city and caused extensive deaths and injuries.
Hiroshima was bombed three days earlier, on 6 August, by the uranium gun-type weapon Little Boy. Nagasaki was not the original target for that mission: Kokura had been selected as the primary target, but cloud and smoke obscured visibility. The aircraft therefore proceeded to its secondary target, Nagasaki.
The bombings occurred alongside the Soviet Union's entry into the war against Japan. Japan announced its decision to accept the Potsdam Declaration days later, although historians continue to debate the relative importance of the atomic attacks, the Soviet invasion, and internal Japanese politics.