Which phase of Operation Downfall was planned to invade southern Kyūshū?

Operation Olympic was the phase of Operation Downfall planned to invade southern Kyūshū.

Olympic was scheduled to begin in November 1945. Allied forces intended to capture the southern third of Kyūshū, Japan’s southernmost main island, and use the area’s airfields to support later operations. Okinawa, captured earlier in 1945, was planned as a major staging area.

The second phase of Downfall was Operation Coronet, which was planned for spring 1946 against the Kantō Plain near Tokyo on Honshū. The two operations were designed as a sequence: Olympic would establish a foothold and air bases, while Coronet would strike toward Japan’s political center.

Japan’s surrender made both operations unnecessary. The plans were developed amid expectations that an invasion would be fiercely resisted, and estimates of possible casualties varied widely. Olympic should not be confused with Operation Overlord, the code name for the Normandy invasion, or Operation Ketsugō, Japan’s defensive plan for the expected Allied attack.