What was the planned spring 1946 Allied operation to invade the Kantō Plain called?

The planned spring 1946 Allied operation to invade the Kantō Plain was called Operation Coronet.

Coronet was the second stage of Operation Downfall, the proposed invasion of Japan. Planners expected it to follow Operation Olympic, which was scheduled for November 1945 against southern Kyushu. Coronet would have attacked the Kantō Plain on Honshu, the main Japanese island, near Tokyo.

The plan depended partly on airfields captured during Olympic. Those bases would have supported the later assault and advance toward the political center of Japan. Operation Downfall was intended to be an enormous amphibious campaign, potentially larger than the Normandy landings.

Coronet was canceled because Japan surrendered before the invasion could begin. Japan’s decision followed the atomic bombings, the Soviet entry into the war against Japan, and the resulting political crisis within the Japanese government. Operation Ketsugō, the Japanese plan for defending the home islands, was the opposing strategy—not an Allied operation.