What was the Allied codename for the planned invasion of Japan before its surrender?

Operation Downfall was the Allied codename for the planned invasion of Japan before its surrender. It was a proposed two-stage campaign intended to force Japan’s capitulation through landings and operations on the Japanese home islands.

The first stage, Operation Olympic, was planned for the invasion of Kyūshū. The second stage, Operation Coronet, was intended to attack the Kantō Plain near Tokyo. Downfall was never carried out because Japan surrendered before the invasion began.

Planning for Downfall shaped Allied expectations about the war’s possible cost, but the atomic bombings of Hiroshima and Nagasaki, the Soviet declaration of war on Japan, and Japan’s internal decision to surrender changed the course of events. Olympic and Coronet therefore remained plans rather than completed operations.