Operation Coronet was the planned second stage of Operation Downfall, aimed at the Kantō Plain near Tokyo. It was intended to follow Operation Olympic, the proposed invasion of southern Kyūshū.
Coronet was tentatively scheduled for 1 March 1946. Allied forces would have landed on beaches near the Kantō Plain, including areas on the Bōsō Peninsula and Sagami Bay, then advanced toward Tokyo. The operation was expected to require a very large concentration of American ground forces, with British Commonwealth reinforcements also considered.
The plan was canceled when Japan surrendered in August 1945. Because Coronet never occurred, its projected troop numbers, objectives, and casualty estimates remained planning figures rather than battlefield results. This distinction matters: many popular accounts describe predicted losses as though they were actual casualties.
Coronet's name is sometimes confused with Olympic, but the two had different targets and stages. Olympic focused on Kyūshū, while Coronet focused on the Tokyo region of Honshu. Together, they formed the main land-invasion concept within Operation Downfall.