What was the codename for the planned Allied invasion of Japan in World War II?

Operation Downfall was the codename for the planned Allied invasion of Japan in World War II.

The proposed operation had two major stages. Operation Olympic was planned as an invasion of southern Kyushu in November 1945, while Operation Coronet was planned for the Kanto Plain near Tokyo in March 1946. Together, these operations formed Operation Downfall.

The invasion plans were never carried out because Japan surrendered in August 1945. The atomic bombings of Hiroshima and Nagasaki, the Soviet entry into the war, Japan’s military situation, and the political decision to accept the Allied terms ended the need for the invasion.

Operation Downfall is often confused with Operation Overlord, the Allied invasion of Normandy in June 1944. Olympic and Coronet were not alternative names for Downfall; they were its component operations. The scale of the planned campaign helps explain why Allied leaders prepared for a potentially costly invasion even as Japan’s surrender was being negotiated.