Kokura was the primary target before Nagasaki on the Bockscar mission of August 9, 1945.
B-29 Bockscar carried the Fat Man bomb and approached Kokura first. The crew needed visual conditions to identify the target, but clouds and smoke obscured the city. Smoke from nearby fires, including the previous day’s raid on Yahata, contributed to the poor visibility.
After several attempts, the aircraft left Kokura and flew to Nagasaki, the mission’s secondary target. A break in the cloud cover allowed the crew to make a visual approach there, despite limited fuel. Fat Man was released over the Urakami Valley at 11:02 a.m. local time.
The phrase “Kokura’s luck” is often used for this event, but it is a later popular expression rather than the name of an official operation. Kyoto was considered during target planning but was removed from the final list.