As the weary Marines finally tried to get some sleep, all along their irregular line of foxholes, two things were very clear to them: they had forced a precarious beachhead in the teeth of bitter enemy fire, and a long, tough battle obviously lay ahead.
While the thoughts of the riflemen focused on survival and the immediate ground in front of them, the senior command echelons saw the initial success of the landings as a culmination of months of planning, training, and organization for a strategic strike on a crucial Japanese stronghold. The opportunity for this sprang from earlier Central Pacific victories.
The Marine conquest of Tarawa in the Gilbert Islands in November 1943, followed by the joint Marine-Army capture of Kwajalein and Eniwetok atolls in the Marshall Islands in January-February 1944, had broken the outer ring of Japanese defenses and set the stage for succeeding operations.
These earlier victories had moved up the entire American operational timetable for the Central Pacific by three valuable months. After discussions of various alternatives (such as an attack on the vast Japanese base at Truk), the Joint Chiefs of Staff had settled on the next objective: the Mariana Islands. There were to be three principal targets: Saipan, Tinian, and Guam. It was a daring decision, for Saipan was 1,344 miles from the Marshalls and 3,226 miles from Hawaii, but only 1,250 miles from Japan. Furthermore, the islands were linchpins in the revised inner defense line which the Japanese felt they absolutely had to hold after their previous losses in the Central and Southwest Pacific.
Saipan represented a whole new kind of prickly problem for an American assault. Instead of a small, flat coral islet in an atoll, it was a large island target of some 72 square miles, with terrain varying from flat cane fields to swamps to precipitous cliffs to the commanding 1,554-foot-high Mount Tapotchau. Moreover, the Japanese considered it “their own territory,” in spite of the fact that it was legally only a mandate provided by the terms of the Versailles Treaty following World War I. The fact that Japan held the islands led it to install a policy of exclusion of all outsiders and the start of military construction, forbidden by the treaty, as early as 1934.
Attacking a formidable objective such as Saipan called for complex planning and much greater force than had previously been needed in the Central Pacific. An elaborate organization was therefore assembled. Admiral Raymond A. Spruance was in overall command of the force detailed to invade the Marianas as well as the naval units needed to protect them. Admiral Turner was in command over the amphibious task force, while Marine Lieutenant General Holland M. Smith was to direct the landing forces on Saipan and then on the neighboring island of Tinian. (A similar command structure, but with different combat units, was set up for the attack on Guam to the south.)
The operation plan for Saipan, code-named Forager, called for an assault on the western side of the island, with the 2d Marine Division on the left and the 4th Marine Division on the right. The Army’s 27th Infantry Division was in reserve, ready to be fed into the battle if needed. While each of the two Marine divisions had previously fought as a complete unit, the 27th had experienced only two minor landings (at Makin and Eniwetok islets) for some of its regiments and battalions.
The intensive training for these three divisions took place in the Hawaiian Islands with Major General Harry Schmidt’s 4th Marine Division on Maui, Major General Thomas E. Watson’s 2d Marine Division on the “Big Island” of Hawaii, and Army Major General Ralph C. Smith’s 27th Infantry Division on Oahu. As Lieutenant Chapin described it:
(These) months were busy, hard-working ones. The replacements that arrived to fill the gaps left by Namur’s casualties (in the Kwajalein battle) had to be trained in all the complexities of field work. Most of these replacements were boys fresh from boot camp, and they were ignorant of everything but the barest essentials. Week after week was filled with long marches, field combat problems, live firing, obstacle courses, street fighting, judo, calisthenics, night and day attacks and defenses, etc. There were also lectures on the errors we’d made at Namur. Added emphasis was placed on attacking fortified positions. We worked with demolition charges of dynamite, TNT, and C-2 [plastic explosive], and with flame throwers till everyone knew them forward and backward.
The month of May 1944 brought final maneuvers and practice landings for all three divisions. The operation plan looked neatly and efficiently organized on paper. In practice it looked different to that lieutenant: