Operation Causeway was a US military plan for a massive invasion of Taiwan in the final days of the Pacific War. To occupy Taiwan, the US 10th Army was formed as the main landing force in June 1944, with General Chester William Nimitz in command. The targets were Southern Taiwan and Amoy, from which the Allied forces could bomb Japan, support the China theatre, and cutoff sea and air traffic between Japan and Southeast Asia. The operational plans were drawn during the months from July to September. The Allied forces needed were estimated to be over 560,000 troops. This essay examines the history of Operation Causeway, including the formation of 10th Army, the military objectives, the scale and components of forces, the landing plans, and the reasons why the operation was eventually abandoned.