Operation Olympic was the planned Allied invasion of southern Kyushu if Japan had not surrendered in 1945.
Olympic was the first stage of Operation Downfall, the broader proposed invasion of the Japanese home islands. It was scheduled for November 1945 and aimed to seize the southern part of Kyushu, Japan’s southernmost main island. Allied planners expected captured airfields there to support a later assault.
The second stage, Operation Coronet, was planned for the Kantō Plain near Tokyo and was tentatively scheduled for spring 1946. Olympic and Coronet together would have required enormous numbers of troops, ships, aircraft, and supplies.
The invasion plans were canceled after Japan surrendered. The decision followed the atomic bombings of Hiroshima and Nagasaki, the Soviet declaration of war, and the Soviet invasion of Japanese-held Manchuria. Because the operation never took place, casualty estimates for it remain projections rather than battlefield totals.