What was the codename for the planned second phase of the Allied invasion of Japan in 1946?

Operation Coronet was the planned second phase of the Allied invasion of Japan in 1946.

Coronet was designed to attack Honshu, Japan’s largest island, through the Kantō Plain south of Tokyo. Planning documents tentatively scheduled the operation for March 1, 1946, after the proposed first phase, Operation Olympic, had secured southern Kyushu.

The projected assault would have been larger than Olympic. American forces planned landings near Kujūkuri Beach and Hiratsuka, followed by an advance toward Tokyo. Up to 45 U.S. divisions were assigned to the initial and follow-up stages in some plans, although exact force estimates changed as planning continued.

Japan’s surrender in August 1945 made Coronet unnecessary. The codename is sometimes mistaken for Operation Downfall, but Downfall was the overall invasion plan. Olympic and Coronet were its two component phases.