What was the Japanese defensive plan for an expected Allied invasion of the Home Islands?

Operation Ketsugo was Japan’s defensive plan for an expected Allied invasion of the Home Islands.

The Japanese high command planned to concentrate forces against the first expected landings, especially in southern Kyushu. The strategy sought to inflict such heavy losses that the Allies might accept a negotiated settlement rather than continue toward total occupation.

Japanese preparations included mobilizing civilians, stockpiling weapons, deploying aircraft for kamikaze attacks, and organizing suicide boats and underwater units. The plan reflected the leadership’s belief that a decisive homeland battle could change the political outcome even though Japan’s military position was deteriorating.

Ketsugo was never tested because the planned invasion did not occur. The corresponding Allied plan was Operation Downfall, whose first phase, Olympic, was aimed at Kyushu. The Japanese and Allied plans are often confused because both names refer to proposed operations rather than battles that actually happened.