Kokura was the primary target that the B-29 Bockscar failed to bomb before attacking Nagasaki.
On August 9, 1945, Bockscar carried the atomic bomb code-named Fat Man. The mission plan designated Kokura as the primary target, but clouds and smoke obscured the city and prevented the crew from making the required visual bombing run. The aircraft then proceeded to its secondary target, Nagasaki.
Nagasaki was also partly covered by cloud, but a brief opening allowed the bombardier to identify the aiming point. Fat Man detonated over the city at about 11:02 a.m. local time. The attack occurred only three days after the bombing of Hiroshima and amid the Soviet Union’s entry into the war against Japan.
The surrender announcement followed on August 15. Historians continue to debate the relative weight of the atomic bombings, the Soviet invasion, and other factors in Japan’s decision, so the bombing sequence should not be treated as a single-cause explanation.