What was the planned Allied invasion of Tokyo and the Kantō Plain called in 1945?

The planned Allied invasion of Tokyo and the Kantō Plain was called Operation Coronet.

Coronet was the second major phase of Operation Downfall, the proposed invasion of Japan’s home islands. Planners intended it to follow Operation Olympic, which would have attacked southern Kyushu in November 1945. Coronet was tentatively scheduled for March 1946 and would have targeted the Kantō Plain near Tokyo on Honshu.

The operation was never launched because Japan surrendered in August 1945 after the atomic bombings of Hiroshima and Nagasaki and the Soviet Union’s entry into the war against Japan. Its cancellation spared the planned invasion forces from the enormous casualties that military planners feared.

Operation Coronet is often confused with Operation Downfall because Downfall was the overall invasion plan. It is also confused with Olympic, the first phase directed at Kyushu. Operation Ketsugō was different again: it was Japan’s own defensive strategy for resisting an Allied invasion. These names describe plans that remained unrealized after Japan’s surrender.