What was the code name for the first planned phase of the proposed invasion of Japan?

Operation Olympic was the code name for the first planned phase of the proposed invasion of Japan.

Olympic was designed as an amphibious assault on Kyūshū, the southernmost of Japan's four main islands. U.S. planners expected the operation to begin on November 1, 1945, if Japan continued fighting. The plan included landings on several beaches and the capture of airfields needed for later operations.

Olympic was one part of Operation Downfall, the overall American plan for invading the Japanese home islands. The second phase, scheduled for March 1946, was called Operation Coronet and targeted the Kantō Plain near Tokyo.

Neither Olympic nor Coronet took place. Japan accepted the Potsdam Declaration in August 1945, following the atomic bombings of Hiroshima and Nagasaki and the Soviet Union's entry into the war. The cancellation of the invasion avoided the enormous casualties that planners expected from an assault on Japan.