The powerful forces of the United States Navy (USN), Marine Corps, and Army advanced inexorably against Imperial Japan in 1944. Following massive interdiction of Japanese merchant shipping by American submarines and multiple naval victories, the Americans stood poised to liberate the Philippines, then move on to locations closer to the Japanese home islands.
In early 1944, arguments raged over the best approach to the "strategic triangle" created by Formosa, Luzon, and China. Finally, on March 12th, the Joint Chiefs of Staff – consisting of Admirals William D. Leahy and Ernest J. King, and Generals George C. Marshall and Henry H. "Hap" Arnold - issued a directive picking the next target: "[T]he most feasible approach to the Formosa-Luzon-China area is by way of Marianas-Carolines-Palau-Mindanao area, and that the control of the Marianas-Carolines-Palau area is essential to the projection of our forces into the former area, and their subsequent effective employment therefrom."
The Americans' plans focused on three islands near the southern end of a 15-island, north to south aligned island chain: Saipan, Tinian, and Guam. These islands, relatively large, offered space for the construction of large air bases within strategic bomber range of Japan itself, as well as closer targets.
The Japanese also recognized the strategic importance of the Mariana Islands, and Saipan in particular, given its location just 1,272 miles from Tokyo itself. This would place the Japanese capital well within the 3,250 mile range of the Boeing B-29 Superfortress. With these facts in their possession and the Marianas as one of the Americans' most logical next choices, the Japanese worked to move both reinforcements and materials for new fortifications to the southern Marianas in early 1944.
With that, the stage was set for the kind of deadly amphibious operations that would take place not only on the Marianas but also Iwo Jima and Okinawa after it.
