What was the planned first phase of Operation Downfall called?

The planned first phase of Operation Downfall was called Operation Olympic.

Operation Downfall was the proposed Allied invasion of Japan’s home islands if Japan did not surrender. Olympic was scheduled for November 1945 and would have targeted southern Kyūshū, Japan’s southernmost main island. Allied planners intended to use captured positions there to support a later attack farther north.

The second phase was Operation Coronet, planned for spring 1946 against the Kantō Plain near Tokyo on Honshū. Together, Olympic and Coronet formed the overall Downfall plan.

Japan’s surrender made the invasion unnecessary. The atomic bombings of Hiroshima and Nagasaki, the Soviet entry into the war against Japan, and Japan’s decision to accept the Allied terms all contributed to the cancellation of Downfall. Because the invasion never occurred, its casualty estimates remain hypothetical rather than recorded battlefield totals.