In Operation Downfall, the planned Allied invasion Operation Olympic targeted Kyūshū.
Olympic was intended to seize the southern part of Kyūshū beginning on 1 November 1945. Allied planners hoped to use the captured area as a staging ground for the later invasion of Honshū, Japan’s largest island. That second operation, called Coronet, was planned for the Kantō Plain near Tokyo.
The operation would have involved a very large naval and ground force. Fourteen U.S. divisions and a division-equivalent force were scheduled for the initial landings, supported by an armada including aircraft carriers, battleships, and hundreds of destroyers and destroyer escorts.
Kyūshū was chosen partly because its southern regions offered locations for airfields and landing beaches. Japanese defenses were strengthened as planners recognized the likely invasion zones. Japan’s surrender in August 1945 ended the need for Olympic, so the planned landings never occurred. Kyūshū instead became an important part of postwar Japan without serving as an Allied battlefield.