Operation Coronet was the planned second phase of Operation Downfall, the Allied invasion plan for Japan.
Coronet was scheduled for 1 March 1946 and was designed to follow Operation Olympic, the proposed invasion of southern Kyūshū. Its target was the Kantō Plain on Honshū, the main Japanese island, including the area around Tokyo. Capturing this region would have placed the Japanese capital and major transport networks under Allied control.
Operation Downfall was divided into the two stages because planners expected that the first invasion would provide bases and weaken Japan’s defenses before the larger assault near Tokyo. Allied commanders studied beaches, logistics, airfields, shipping, and possible Japanese resistance in detail.
Japan surrendered before either operation began. Coronet is therefore a planned operation rather than a battle. It should not be confused with Operation Olympic, which was the first phase, or with Operation Causeway, an earlier proposed assault on Taiwan.