Which planned operation targeted Japan's Kanto Plain near Tokyo in 1946?

Operation Coronet was the planned Allied invasion of Japan's Kanto Plain near Tokyo in 1946. It was intended to be the second major phase of Operation Downfall, following the proposed invasion of Kyushu.

Coronet was tentatively scheduled for 1 March 1946, known as Y-Day in the planning documents. U.S. forces expected to land on beaches near the Kanto Plain, including areas around Sagami Bay and the Boso Peninsula, then advance toward Tokyo.

The operation was designed to use airfields and staging areas captured during Operation Olympic. Coronet would have required enormous reinforcements and was projected to be larger than the initial Kyushu operation. Plans included major U.S. Army and Marine formations, with possible British Commonwealth participation.

Coronet never took place because Japan surrendered in August 1945. The name is often confused with Downfall: Downfall was the overall invasion plan, while Coronet was its proposed second phase. Operation Ketsugo was Japan's defensive response to the expected invasion.