What was the codename for the planned Allied invasion of Honshu near Tokyo in 1946?

Operation Coronet was the codename for the planned Allied invasion of Honshu near Tokyo in 1946.

Coronet was the second phase of Operation Downfall, the proposed invasion of the Japanese home islands. Planners intended to land on the Kantō Plain, the broad region surrounding Tokyo, on March 1, 1946, after the earlier Operation Olympic campaign in southern Kyūshū.

The plan called for forces to land around Sagami Bay and the Bōsō Peninsula, then advance toward Tokyo. Up to 45 U.S. divisions were associated with the projected operation, making it larger than the planned first phase and potentially larger than the Normandy landings.

Coronet was canceled when Japan surrendered in August 1945. Because the invasion never occurred, its projected troop levels and casualties remain planning estimates rather than wartime results.