Operation Coronet was the planned second stage of Operation Downfall, aimed at Japan's Kanto Plain near Tokyo.
Coronet was tentatively scheduled for March 1, 1946, after Operation Olympic had captured southern Kyushu and established additional bases. The proposed landings would have taken place at beaches on the Boso Peninsula and Sagami Bay, followed by an advance toward Tokyo.
Planning envisioned a very large force. Up to 45 U.S. divisions were assigned to the initial landing and follow-up, making Coronet larger than Olympic. By comparison, the initial Normandy landings in 1944 used twelve divisions. These figures describe plans, not forces that actually fought.
Japan surrendered before Olympic began, so Coronet was canceled. The name is sometimes confused with Downfall, which referred to the entire invasion plan, or Olympic, which referred specifically to the earlier Kyushu phase.