Operation Causeway

Operation Causeway was a planned United States invasion of Formosa (Taiwan) during World War II. Formosa was a Japanese colony since the nineteenth century. It was seen as a possible next step in the planned Allied advance across the Pacific after the capture of the Marianas in summer 1944.

Proposal and purpose
According to the planners, Formosa would have provided a suitable base for the strategic bombing campaign against Japan as well as a staging area for the foreseen invasion of the Japanese home islands. Its planned capture was also seen as a symbolic demonstration of American support for the continued participation of China in the war against Japan.

Support and opposition
Admiral Ernest J. King, Chief of Naval Operations, was a high-profile supporter of the Formosa plan. He was opposed by General Douglas MacArthur, commander-in-chief of the South West Pacific Area, who pushed for the invasion of Luzon in the Philippines and argued for bypassing Formosa. Admiral Raymond Spruance, commanding the Fifth Fleet, concurred with MacArthur that Operation Causeway was unrealistic without further significant reinforcements in the Pacific theater; instead, Spruance proposed the capture of Iwo Jima and Okinawa, the latter an island smaller than Formosa and therefore not requiring additional troops diverted from Europe.

Rejection
At a high-level meeting in Pearl Harbor in July 1944, President Roosevelt conferred with General MacArthur and Admiral Chester W. Nimitz, Commander-in-Chief of the Pacific Fleet. Both commanders balked at Operation Causeway and advised the president accordingly. Instead MacArthur's plan for the invasion of Luzon and Spruance's proposals were put into operation. Causeway was not rejected at the Pearl Harbor Conference in July 1944, although McArthur opposed it and Nimitz was at best lukewarm. ‘In San Francisco, Spruance recalled, [Admiral Ernest J.] King continued to argue the case for CAUSEWAY, “but finally gave in and said he would recommend [Luzon-Iwo Jima-Okinawa] to the Joint Chiefs of Staff in Washington, which he did.” On October 3, the JCS issued new directives sending MacArthur into Luzon in December 1944, the marines into Iwo Jima in January 1945, and a large combined navy-army-marine force into Okinawa in March 1945. That fixed the sequence of major operations for the last year of the Pacific War.’  [Twilight of the Gods: War in the Western Pacific, 1944-1945 (Vol. 3) (The Pacific War Trilogy) by Ian W. Toll, published 2020.]