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

Operation Downfall was the Allied code name for the planned invasion of Japan.

The plan was divided into two major phases. Operation Olympic called for an invasion of Kyushu, Japan’s southernmost main island, in November 1945. Operation Coronet was planned for March 1946 and would have targeted the Kantō Plain near Tokyo on Honshu.

Downfall was never carried out because Japan accepted the Allied terms in August 1945 and formally surrendered in September. The atomic bombings of Hiroshima and Nagasaki, the Soviet entry into the war against Japan, and Japan’s internal decision to accept surrender all occurred before Olympic began.

The planned invasion helps explain why Allied leaders prepared for a potentially enormous campaign even after Germany had surrendered. Estimates of casualties varied widely, and historians continue to debate how much weight each factor carried in Japan’s decision. Operation Olympic and Operation Coronet were components of Downfall, not alternative names for the whole plan.