Kokura was the original target of the Fat Man bomb before the mission diverted to Nagasaki.
On August 9, 1945, the B-29 Bockscar carried Fat Man toward Kokura, an industrial city in northern Kyushu. The crew made several attempts to locate the aiming point, but cloud cover and smoke prevented the required visual bombing run.
Because the aircraft had limited fuel, the crew proceeded to the secondary target, Nagasaki. A break in the clouds eventually allowed the bomb to be released. The weapon detonated over the Urakami Valley, north of the city’s intended aiming point, rather than directly over central Nagasaki.
Kokura’s near-miss later became a memorable example of how weather, smoke, fuel, and operational decisions shaped the atomic missions. The city was not spared because of a formal cancellation known at the time as “Kokura’s luck”; the diversion resulted from immediate flight conditions and mission constraints.