In Operation Downfall, what was the code name for the planned 1946 invasion of Japan’s Kanto Plain?

Operation Downfall called the planned 1946 invasion of Japan’s Kanto Plain Operation Coronet.

Coronet was intended as the second stage of the Allied invasion plan for Japan. Its target was the Kanto Plain on Honshu, the country’s largest island and the region containing Tokyo. The operation was tentatively scheduled to begin on March 1, 1946.

The plan depended on the earlier capture of southern Kyushu in Operation Olympic. Airfields and supply bases seized during Olympic would have supported the much larger drive toward Tokyo. Coronet was expected to require an enormous force, including American armies and planned British Commonwealth reinforcements.

The proposal was canceled after Japan accepted the Allied surrender terms in August 1945. Coronet is therefore a planned operation, not a battle that occurred. Its parent plan, Operation Downfall, is sometimes mistakenly treated as an executed campaign.