What was the Allied plan for a full-scale invasion of Japan if the country refused to surrender in 1945?

Operation Downfall was the Allied plan for a full-scale invasion of Japan if Japan refused to surrender in 1945. It was the proposed campaign for occupying the Japanese home islands and consisted of two major stages.

The first stage, Operation Olympic, called for landings on Kyushu, Japan’s southernmost main island, in November 1945. The second, Operation Coronet, was planned for the Kanto Plain near Tokyo in March 1946. Together, these operations would have required enormous Allied forces and were expected to produce severe casualties on both sides.

Operation Downfall was never carried out because Japan surrendered in August 1945. Planning for the invasion nevertheless influenced Allied military preparations, including the buildup of troops, ships, aircraft, and supplies in the Pacific. The atomic bombings of Hiroshima and Nagasaki, the Soviet declaration of war, Japan’s worsening military position, and the emperor’s intervention changed the course of events before Olympic could begin. Olympic and Coronet are therefore parts of Downfall, not alternative names for the entire plan.