What invasion plan was prepared for a possible Allied attack on Japan’s home islands in 1945?

Operation Downfall was the planned Allied invasion of Japan’s home islands in 1945.

The overall plan had two major stages. Operation Olympic would have invaded southern Kyushu in November 1945, while Operation Coronet would have targeted the Kanto Plain near Tokyo in March 1946. Together, these operations were called Operation Downfall.

The plan was never carried out because Japan surrendered after the atomic bombings, the Soviet Union’s declaration of war, and intense internal debate within the Japanese government. Allied leaders expected the invasion to be extremely costly because Japan was preparing military and civilian defenses throughout the home islands.

Operation Downfall is often confused with Operation Olympic, but Olympic was only the first phase of the larger plan. It is also distinct from Operation Overlord, the Allied invasion of Normandy in June 1944. The cancellation of Downfall prevented the planned land campaign against Japan from taking place.