What was the codename for the planned 1946 Allied invasion of Japan’s main island, Honshu?

Operation Coronet was the codename for the planned 1946 Allied invasion of Honshu, Japan’s main island.

Coronet formed the second stage of Operation Downfall, the proposed Allied invasion of the Japanese home islands. It was intended to land in the Kanto Plain near Tokyo, following Operation Olympic’s planned invasion of southern Kyushu in November 1945.

The tentative start date for Coronet was March 1, 1946. Allied planners expected the operation to require enormous forces, including major American armies and possible British Commonwealth reinforcements.

Japan’s surrender made both operations unnecessary. Operation Olympic was the Kyushu phase, while Operation Downfall was the overall invasion plan. These names are therefore related, but they do not identify the same planned operation.