Operation Setting Sun was the name given to the theoretical and planned Allied invasion of Japan, set to have occurred either in late 1929 or early 1930 using American, Siberian, Colombian and Oceanian soldiers to end the Pacific War. The plan was regarded as one of the most ambitious operations in military history, and used Japan's own attempted suppressant invasion of the United States in 1925 as its model. However, the operation was still only in the early planning phases when the Hilo Accords were signed, thus ending the planning process.
The plan relied on three separate phases - Columbia, the capture and occupation of the Chinese Island of Formosa to cut Japan's forces at home and on the Chinese mainland off from one another; Feature, the ground invasion coupled with heavy aerial bombardment of Kyushu; and Trojan, the land invasion of Honshu coupled with a naval and aerial firebombing of Edo City. The plan was drawn up under President Robinson in the event that American and Allied forces would be in position to attack Japan following his hoped-for reelection victory, and was maintained through the transition to the Hoover administration in 1929.