What was the Allied operation planned to invade southern Kyushu if Japan had not surrendered?

Operation Olympic was the Allied operation planned to invade southern Kyushu if Japan had not surrendered.

Olympic formed the first stage of Operation Downfall, the proposed Allied invasion of Japan’s home islands. It was scheduled for November 1945 and aimed to capture the southern third of Kyushu, Japan’s southernmost main island. Allied planners intended to use Okinawa as a staging area and to seize airfields for later operations.

The second stage of Downfall was Operation Coronet, planned for the Kanto Plain near Tokyo in spring 1946. Because Japan surrendered in August 1945, neither operation was carried out.

Operation Olympic should not be confused with Operation Downfall, which was the overall invasion plan, or Operation Ketsugō, Japan’s defensive plan for resisting an Allied landing. Estimates of casualties for a possible invasion varied widely, but the projected fighting was expected to be extremely costly for both sides.