What was Japan’s planned defensive operation against an Allied invasion of its home islands in 1945?

Operation Ketsugō was Japan’s planned defensive operation against an Allied invasion of its home islands in 1945.

Japanese leaders expected the Allies to attack the home islands after the capture of Okinawa. Ketsugō was designed as a decisive national defense, with Japanese forces attempting to inflict such heavy losses that the United States might abandon unconditional surrender and accept an armistice or negotiated settlement.

The plan focused especially on Kyūshū, where Japanese intelligence correctly anticipated likely landing areas. Japan intended to concentrate troops, aircraft, naval forces, and civilians in a desperate defense. Propaganda campaigns called for a mass national struggle, while military planners prepared for widespread use of kamikaze aircraft and improvised weapons.

Operation Ketsugō was never executed because Japan surrendered before the planned Allied invasion. The corresponding Allied plan, Operation Downfall, had two phases: Olympic against southern Kyūshū and Coronet against the Kantō Plain near Tokyo. The surrender made both invasion operations unnecessary.