What was the Allied plan for a full-scale invasion of Japan that was canceled after Japan surrendered?

Operation Downfall was the Allied plan for a full-scale invasion of Japan that was canceled after Japan surrendered. It was designed for a two-stage assault on the Japanese home islands.

The first stage, Operation Olympic, was scheduled to land on southern Kyushu in November 1945. The second, Operation Coronet, was planned for the Kanto Plain near Tokyo in spring 1946. The proposed campaign would have required enormous naval, air, and ground forces and was expected to produce severe casualties on both sides.

Downfall was never executed. Japan’s surrender followed the atomic bombings of Hiroshima and Nagasaki, the Soviet Union’s entry into the war against Japan, and the resulting political crisis in Tokyo. Because the invasion plans were abandoned, later casualty estimates are hypothetical rather than recorded battlefield totals. Operation Downfall is therefore an important example of a major military operation that shaped wartime planning without ever taking place.