Which Japanese operation planned the defense of the home islands against an Allied invasion in 1945?

Operation Ketsugō was Japan’s plan to defend the home islands against the expected Allied invasion in 1945. Japanese leaders anticipated attacks on Kyushu and prepared for an all-out national defense.

The plan was developed in response to Operation Downfall, the Allied proposal to invade Japan. Its first expected target was Kyushu, where Operation Olympic was scheduled to land in November 1945. Japanese commanders recognized the likely invasion areas and concentrated forces, aircraft, boats, and civilians for resistance.

Ketsugō was never tested in battle because Japan surrendered before Olympic began. It is sometimes confused with Downfall, but the names referred to opposing plans: Downfall was the Allied invasion concept, while Ketsugō was Japan’s defensive strategy. The planned conflict also helps explain why casualty estimates for an invasion varied so widely and why the surrender decision was historically consequential.