Operation Coronet was planned to invade the Kanto Plain near Tokyo.
Coronet was the second stage of Operation Downfall, the proposed Allied invasion of Japan. It was scheduled for spring 1946 after Operation Olympic had captured positions on Kyushu. The Kanto Plain offered access to Tokyo and the surrounding political, industrial, and population centers of eastern Honshu.
The plan called for a large amphibious assault around the Kanto region, supported by forces from the United States and the British Commonwealth. Its scale would have made it one of the largest military operations ever planned. Japan's surrender in August 1945 canceled both Coronet and Olympic before either could begin.
The Kanto Plain should not be confused with the Nobi Plain around Nagoya or the Osaka Plain farther west. It is Japan's largest plain and includes Tokyo and much of the surrounding metropolitan region. In the context of Operation Downfall, the phrase “near Tokyo” is the key geographic clue.