Chapter 2 : American and Japanese Preparations1
As the tactical plans were taking shape, the divisions slated for the Saipan operation began training for the impending battle. Ships were summoned to Hawaii to carry the invasion force to its destination. While the Americans gathered strength for the massive effort to seize the Marianas, the enemy looked to the defenses of the Central Pacific. In Hawaii, Marines and Army infantrymen practiced landing from LVTs in preparation for the Saipan assault. At the objective, Japanese troops were working just as hard to perfect their defenses.
The Importance of Training and Rehearsals
The Marine and Army units selected to conquer Saipan underwent training in the Hawaiian Islands designed to prepare them for combat in the jungle, cane fields, and mountains of the Mariana islands. The scope of training matched the evolution of tactical plans, as individual and small unit training gave way to battalion exercises, and these, in turn, were followed by regimental and division maneuvers. The 2nd Marine Division, encamped on the island of Hawaii, did its training in an area that closely resembled volcanic Saipan. After its conquest of northern Kwajalein, the 4th Marine Division arrived at the island of Maui to begin building its living quarters and ranges—tasks which coincided with training for FORAGER. Both construction and tactical exercises were hampered by the nature of the soil, a clay which varied in color and texture from red dust to red mud. The 27th Infantry Division, on the island of Oahu, emphasized tank-infantry teamwork and the proper employment of JASCO units during amphibious operations. The XXIV Corps Artillery was in the meantime integrating into its ranks the coast artillerymen needed to bring the battalions to authorized strength, conducting firing exercises, and learning amphibious techniques.
Amphibious training got underway in March, when the 2nd Marine Division landed on the shores of Maalaea Bay, Maui. The 4th Marine Division, Corps Troops, and the 27th infantry Division received their practical instruction during the following month. The climax to the indoctrination scheduled by General Watson for his 2nd Marine Division was a “walk through” rehearsal held on dry land. An outline of Saipan was drawn to scale on the ground, the various phase lines and unit boundaries
were marked, thereby enabling the Marines to see for themselves how the plan would be executed. “Yet,” the commanding general recalled, “only a few commanders and staff officers of the thousands of men who participated in this rehearsal knew the real name of the target.”2
On 17 and 19 May, the two Marine divisions took part in the final rehearsals of Northern Troops and Landing Force. The first exercise, conducted at Maalaea Bay, saw the Marines land on the beaches and advance inland, following the general scheme of maneuver for the Saipan operation. The second rehearsal was held at Kahoolawe Island, site of a naval gunfire target range. Although the roar of naval guns added realism to the exercise, the assault troops did not go ashore. After the landing craft had turned back, shore fire control parties landed to call for naval salvos against the already shell-scarred island. The 27th Infantry Division completed its rehearsals between 18 and 24 May. The independent 1/2 and its reinforcing elements climaxed the training cycle with landings at Hanalei Bay.
The rehearsals were marred by a series of accidents en route to Maui that killed 2 Marines, injured 16, and caused 17 others to be reported as missing. In the early morning darkness of 14 May, heavy seas caused the cables securing three Landing Craft, Tank (LCTs) to part, and the craft plummeted from the decks of their parent LSTs. Only one of the boats lost overboard remained afloat. The LCTs mounted 4.2-inch mortars, weapons which would have been used to interdict the road between Garapan and Charan-Kanoa and protect the flank of the 2nd Marine Division.3
Since there was not enough time to obtain replacements for the lost mortars, Admiral Turner decided to rely on the scheduled rocket barrage by LCI(G)s for neutralization of beach defenses. He ordered those LSTs and the LCT that carried the heavy mortars and their supply of ammunition to unload upon their return to Pearl Harbor. As the mortar shells were being put ashore, tragedy struck again.
On 21 May, one of the 4.2-inch rounds exploded while it was being unloaded, touching off a conflagration that enveloped six landing ships. Navy fire-fighting craft tried valiantly to smother the flames, but, though they prevented the further spread of the blaze, they could not save the six LSTs from destruction. The gutted ships had carried assault troops as well as weapons and equipment, so losses were severe. The explosion and fire inflicted 95 casualties on the 2nd Marine Division and 112 on the 4th Marine Division. Replacements were rushed to the units involved in the tragedy, but the new
men “were not trained to carry out the functions of those lost.”4 The destroyed ships, equipment, and supplies were replaced in time for the LST convoy to sail on 25 May, just one day behind schedule. The lost time was made up en route to the objective.
Onward To Saipan
The movement of Northern Troops and Landing Force plus the Expeditionary Troops reserve from Hawaii to Saipan was an undertaking that required a total of 110 transports. Involved in the operation were 37 troop transports of various types, 11 cargo ships, 5 LSDs, 47 LSTs, and 10 converted destroyers.5 Navy-manned Liberty ships, vessels that lacked adequate troop accommodations, were pressed into service as transports for a portion of the 27th Infantry Division. LSTs carrying assault troops, LVTs, and artillery from both Marine divisions set sail on 25 May. Two days later, transports bearing the remainder of the 4th Marine Division and Headquarters, Expeditionary Troops departed, to be followed on 30 May by elements of the 2nd Marine Division. Because of the shortage of shipping, portions of XXIV Corps Artillery were assigned to the transports carrying the assault divisions. Garrison units and Expeditionary Troops reserve were the last units to steam westward.
The transports carrying the Marines sailed to Eniwetok Atoll where they joined the LST convoy. Here additional assault units were transferred from the troop ships to the already crowded landing ships for the final portion of the voyage. One observer, writing of the journey from Eniwetok to Saipan, has claimed that because of the overcrowding, “aggressiveness was perhaps increased,” for “after six crowded days aboard an LST, many Marines were ready to fight anybody.”6 By 11 June, the last of the ships assigned to stage through Eniwetok had weighed anchor to begin the final approach to the objective. Meanwhile, the vessels carrying the 27th Infantry Division had completed their last-minute regrouping at Kwajalein Atoll.
While the vessels bearing General Holland Smith’s 71,034 Marine and Army troops were advancing toward Saipan, the preparatory bombardment of the island got underway. The 16 carriers of Task Force 58 struck first, launching their planes on 11 June to begin a 3 ½-day aerial campaign against Saipan, Tinian, Guam, Rota, and Pagan—the principal islands in the Marianas group. These attacks were originally to have started on the morning of the 12th, but Vice Admiral Marc A. Mitscher, the task force commander, obtained permission to strike one-half day earlier. Mitscher felt that the enemy had become accustomed to early morning raids, so he planned
to attack in the afternoon. A fighter sweep conducted by 225 planes accounted for an estimated 150 Japanese aircraft on the first day, this insuring American control of the skies over the Marianas.
After the Grumman Hellcats departed, a member of the Saipan garrison noted in his diary that: “For two hours the enemy planes ran amuck and finally left leisurely amidst the unparalleledly inaccurate antiaircraft fire. All we could do was watch helplessly.”7 On 12 and 13 June, bombers struck with impunity at the various islands and at shipping in the area. The only opposition was from antiaircraft guns like those on Tinian which “spread black smoke where the enemy planes weren’t.” One of Tinian’s defenders glumly observed: “Now begins our cave life.”8
Admiral Mitscher’s fast battleships opened fire on 13 June, but their long-range bombardment proved comparatively ineffective. With the exception of the USS North Carolina, which a naval gunfire officer of Northern Troops and Landing Force called “one of the best-shooting ships I ever fired,”9 the new battleships tended to fire into areas or at obvious if unimportant targets, rather than at carefully camouflaged weapons positions. Neither crews of the ships nor aerial observers who adjusted the salvos had been trained in the systematic bombardment of shore emplacements. Although these battleships did not seriously damage the Japanese defenses, Admiral Spruance nonetheless believed that their contribution was valuable. The shelling by fast battleships, he later pointed out, “was never intended to take the place of the close-in fire of the old battleships] to which it was a useful preliminary.”10
Seven old battleships with 11 attendant cruisers and 23 destroyers relieved the fast battleships on 14 June to begin blasting Saipan and Tinian. The quality of the bombardment improved, but all did not go according to plan, for the neutralization of Afetna and Nafutan Points proved difficult to attain. Although aircraft assisted the surface units by attacking targets in the rugged interior, the preliminary bombardment was not a complete success. The size of the island, the lack of time for a truly methodical bombardment, the large number of point targets, Japanese camouflage, and the enemy’s use of mobile weapons all hampered the American attempt to shatter the Saipan defenses.
On the morning of 14 June, underwater demolition teams swam toward Beaches Red, Green, Yellow, and Blue, as well as toward the Scarlet Beaches, an alternate landing area north of Tanapag Harbor. This daylight reconnaissance was a difficult mission. Lieutenant Commander Draper L. Kauffman, leader of one of the demolition teams, had told Admiral Turner that “You don’t swim in to somebody’s
beaches in broad daylight,” but swim they did—in spite of Kauffman’s prediction of 50 percent casualties.11 Despite a screen of naval gunfire, which had difficulty in silencing the weapons sited to cover the waters of the Blue and Yellow Beaches, the teams lost two men killed and seven wounded, approximately 13 percent of their total strength. The swimmers reported the absence of artificial obstacles, the condition of the reef, and the depth of water off the beaches. On D-Day, members of these reconnaissance units would board control vessels to help guide the assault waves along the prescribed boat lanes. (See Map 16.)
The heavy naval and air bombardment directed against the Marianas were only a part of the preparations decided upon for FORAGER. Wake and Marcus Islands had been bombed during May in order to protect the movement of Admiral Turner’s warships and transports. Bombs thudded into enemy bases from the Marshalls to the Kuriles in an effort to maintain pressure on the Japanese. Finally, on 14 June, two carrier groups cut loose from Task Force 58 to attack Iwo Jima, Haha Jima, and Chichi Jima in the Volcano-Bonin Islands. These strikes were designed to prevent the enemy from making good his aerial losses by transferring planes from the home islands to the Marianas by way of the Bonins.
Like the attacking Americans, the Japanese defenders were completing their preparations for the Saipan landings. Fully alerted by the air and naval bombardment, the Saipan garrison realized that it soon would be called upon to fight to the death. Lieutenant General Hideyoshi Obata and Vice Admiral Chiuchi Nagumo awaited the arrival of the Marines so that they could execute their portion of the A-GO plan, which called for the destruction of the invaders on the beaches of Saipan.
The Defense of Saipan12
Saipan had long figured in Japanese military plans. As early as 1934, the year before her withdrawal from the League of Nations, Japan had begun work on an airfield at the southern end of Saipan. By 1944, this installation, Aslito airfield, had become an important cog in the aerial defense mechanism devised to guard the Marianas. A seaplane base at Tanapag Harbor was completed in 1935, and during 1940-1941 money was appropriated for gun emplacements, storage bunkers, and other military structures. On the eve of World War II, the Fourth Fleet, with headquarters at
Truk, had responsibility for the defense of the Marianas. The work of building, improving, and maintaining the island fortifications was the task of the 5th Base Force and its attached units, the 5th Communications Unit and 5th Defense Force. Logistical support of the Marianas garrison was turned over to the Fourth Fleet Naval Stores Department and the 4th Naval Air Depot, both located at Saipan. Originally the Marianas forces were to strengthen the defenses of the area and ready themselves for a possible war, but once Japan had begun preparing to strike at Pearl Harbor, the 5th Base Force received orders to lay plans for the capture of Guam.
War came, Guam surrendered, and the Marianas became a rear area as Japanese troops steadily advanced. Since Saipan served primarily as a staging area, a sizeable garrison force was not needed. In May 1943, when the Gilberts marked the eastern limits of the Japanese empire, only 919 troops and 220 civilians were stationed on Saipan. As American forces thrust westward, reinforcements were rushed into the Marianas area.
During February 1944, Kwajalein and Eniwetok Atolls, both important bases, were seized by American amphibious forces. Within the space of three weeks, Saipan became a frontline outpost rather than a peaceful staging area. That portion of the 5th Special Base Force13 located at Saipan, a contingent which now numbered 1,437 men, was too weak to hold the island against a determined assault.
After the collapse of the Marshalls defenses and the withdrawal of fleet units from Truk, the Japanese established the Central Pacific Area Fleet under the command of Vice Admiral Chiuchi Nagumo, who had led the Pearl Harbor raid, the successful foray into the Indian Ocean, and still later the ill-fated expedition against Midway. Nagumo’s headquarters, charged with the defense of the Marianas, Bonins, and Palaus, was subordinate to Admiral Toyoda’s Combined Fleet, now based at Tawi Tawi in the Philippines. The Fourth Fleet, relieved of overall responsibility for the Mandated Islands, retained control over Truk and the other eastern Carolines, as well as the isolated Marshalls outposts. (See Map I. )
Nagumo’s command, however, was an administrative organization unable to exert effective tactical control over the Thirty-first Army, the land force assigned to defend the various islands in the Marianas, Bonins, and Palaus. Initially, Nagumo was appointed supreme commander throughout this sector, but Headquarters, Thirty-first Army objected to being subordinated to a naval officer. By mid-March, Nagumo and Lieutenant General Hideyoshi Obata, the army commander, had sidestepped the issue, each one pledging himself to refrain from exercising complete authority over the other.
Instead of regarding the various island groups as an integrated theater under a unified command, the two officers, in keeping with an Army-Navy
agreement worked out by Imperial General Headquarters,14 chose to treat each island as an individual outpost, to be commanded by the senior Army or Navy officer present. At Saipan, for example, Rear Admiral Sugimura in command of the 5th Special Base Force15 was originally given control over the defense of the island, but Obata reserved the right, in case of an American attack, of either commanding in person or designating a land commander of his own choice. Thus, the compromise left the general free to assume complete charge of the ground defense of any island in immediate danger of being stormed by Americans. Obata could assume overall responsibility for troop dispositions, coastal defense batteries, antiaircraft defenses, beach defenses, and communications. The employment of aircraft and the use of radar, however, would remain beyond his jurisdiction.16
This revision of the Central Pacific command structure reflected the increasing concern with which the Japanese high command regarded the defenses of Saipan and the other islands which lay in the path of the American offensive. Between February and May, two divisions, two independent brigades, two independent regiments, and three expeditionary units were rushed to the Marianas to form the Marianas Sector Army Group of Obata’s Thirty-first Army. Naval strength in the islands was augmented by the arrival of the 55th and 56th Guard Forces17 as well as antiaircraft and aviation units.
Prowling American submarines preyed upon the convoys that carried these reinforcements westward. One regiment of the 29th Division, destined for Guam by way of Saipan, lost about half its men when a transport was torpedoed. Submarines also destroyed a vessel carrying some 1,000 reinforcements to the 54th Guard Force, the unit which had garrisoned Guam since the capture of that island in December 1941. Five of the seven transports carrying elements of Lieutenant General Yoshitsugu Saito’s 43rd Division to Saipan went down en route to the Marianas, but the ships that stayed afloat managed to rescue most of the survivors. Units in this convoy lost about one-fifth of their total complement, most of these casualties from a single regiment. Also destroyed were numerous weapons and a great deal of equipment. These successful undersea operations, strange to relate, resulted in the arrival at Saipan of some unscheduled reinforcements. About 1,500 troops, originally headed for Yap, were rescued when their transports were torpedoed and were added to the garrison of the Marianas bastion instead. Other survivors, members of units bound for the Palau Sector Army Group, also were put ashore at Saipan. In addition to these men, approximately 3,000 troops destined for garrisons on other islands of the Marianas and Carolines, were present on Saipan.18
Work on additional fortifications in the Marianas was handicapped by the
deadly submarines which destroyed vital cargos as efficiently as they claimed Japanese lives. Obata’s chief of staff acknowledged the double effect of the underwater attacks. “The special point of differentiation in the Saipan battle,” he observed late in the campaign, “is that units sunk late in May the troops intended for Yap and the Palaus] and the 8,000 men who landed on 7 June members of the 43rd Division] eventually landed not up to full combat strength ... Moreover, as they were still in the process of reorganization at the time of attack, our fighting strength on Saipan was in the process of flux.”19 Could these ill-equipped troops be put to work building obstacles and gun emplacements? The answer was an emphatic “No.” As the chief of staff pointed out, “unless the units are supplied with cement, steel reinforcements for cement, barbed wire, lumber, etc., which cannot be obtained in these islands, no matter how many soldiers there are, they can do nothing in regard to fortification but sit around with their arms folded, and the situation is unbearable.”20
The submarine campaign did not reach peak intensity in time to prevent the Japanese from building airfields throughout the Marianas. By June 1944, Guam boasted two operational fields and two others not yet completed, Tinian had three airfields with work underway on a fourth, and both Rota and Pagan were the sites of still other flight strips. At Saipan, the old Aslito airfield, now less important than the new Tinian bases, was capable of handling extensive aerial traffic. One emergency strip was built near Charan Kanoa, but another such field, begun at Marpi Point, was as yet unfinished. Work on land defenses, however, was not as far advanced as airfield construction.
The defenders of Saipan planned to defeat the invaders on the beaches, but General Obata also hoped to prepare “positions in depth, converting actually the island into an invulnerable fortress.”21 The coastal defenses sited to cover probable avenues of approach were completed. Five Navy coastal defense batteries on Saipan and one at outlying Maniagassa island guarded the approaches lying between Agingan and Marpi Points. Two of these batteries, one armed with a 120-mm and the other with a 150-mm gun, could join twin-mounted 150-mm pieces near Tanapag in engaging targets off the northwest coast. A 40-mm battery of three guns protected Marpi Point, while Magicienne Bay was blanketed by the fires of four batteries, two of them mounting 200-mm weapons. A lone battery of two 150-mm guns guarded Nafutan Point. Army and Navy dual-purpose antiaircraft weapons reinforced the fires of these batteries, as did the Army artillery units located in southern Saipan.22
Map 15: Saipan, Showing Japanese Defense Sectors
Those beaches judged best suited for amphibious landings were guarded by powerful forces backed by comparatively feeble local reserves. A short distance inland, the enemy had prepared a second line designed to contain penetrations of the coastal perimeter until a counterattack could be organized. A tank regiment shouldered the main burden of eradicating any American salient, but Obata also held out four rifle companies and two shipping companies as a general reserve to join in counterthrusts, When the Japanese commander turned his attention to the rugged interior of Saipan, he discovered himself to be short of critical building materials, vital time, and necessary engineer units. The invulnerable fortress depicted by Obata was not fully realized, but he nevertheless selected certain redoubts, most of them in forbidding terrain. If the Americans smashed the first two lines, caves, gorges, and dense thickets would have to serve as pillboxes, antitank barriers, and barbed wire.
The Japanese plan of deployment divided Saipan into four sectors, three under Army command and one nominally entrusted to the Navy. Since 25,469 soldiers and only 6,160 sailors23 were serving on the island, the division of responsibility seems equitable, but many of the naval units specialized in supply or administration, so Army troops were stationed in all areas. The northern sector, which lay beyond a line drawn across the island just south of Tanapag, was protected by two battalions of the 135th Infantry Regiment plus reinforcing elements. South of this zone, bounded on the east by a line drawn down the axis of the island and on the south by another line that stretched inland from just south of Garapan to include Mount Tapotchau, was the Navy sector, manned by a reinforced battalion from the 136th Infantry Regiment and the 5th Special Base Force. The naval unit included the recently arrived 55th Guard Force as well as the Yokosuka 1st Special Naval Landing Force, which had served at Saipan since the autumn of 1943. The central sector, defended by elements of the 136th Infantry Regiment, included that portion of Saipan that lay west of the spine of the island and north of a line drawn below Afetna Point. The remainder of the island was organized as the southern sector. Here Obata concentrated the bulk of his artillery and antiaircraft units, the 47th Independent Mixed Brigade, the 9th Tank Regiment, and the remainder of his 43rd Division, which included a general reserve, certain shipping companies, and stragglers from several miscellaneous units. (See Map 15.)
Although Saipan and her neighboring islands were heavily reinforced, Japanese planners felt that the Palaus rather than the Marianas would be Nimitz’ next objective. According to Admiral Toyoda, commander of the Combined Fleet, “while the possibility of your offensive against the Marianas was not ignored or belittled, we thought the probability would be that your attack would be directed against Palau, and that was the reason for our
adoption of the A-GO operation plan, which was to our advantage because of the shorter distance involved and would eliminate the need of tankers to some extent. ...”24
General MacArthur’s sudden descent upon Biak in the Schouten Islands off New Guinea, an operation that began on 27 May, diverted attention from both the Palau chain and the Marianas. Since Biak possessed airfields from which planes could attack American ships moving northward into the Palaus, the Japanese prepared the KON plan, a scheme for reinforcing the threatened island. The first attempts to aid the embattled garrison ended in frustration, so Toyoda decided to commit the modern battleships Yamato and Musashi, the most powerful surface units of the Japanese fleet. As this strengthened KON task force was assembling, American carriers hit the Marianas, so the enemy admiral left the reinforcement of Biak to destroyers, barges, and other small craft and ordered his forces to execute A-GO,
On 13 June, Admiral Jisaburo Ozawa led his Mobile Fleet, the A-GO striking force, from Tawi Tawi toward the Marianas. The Yamato and Musashi, with their attendant warships, steamed northward to a refueling rendezvous in the Philippine Sea, where they would join Ozawa’s armada. Nimitz’ blow at the Marianas caught the enemy somewhat off balance, for the ships dispatched toward Biak and the planes massed in the Palaus and eastern Carolines would have to be redeployed if they were to take part in the scheduled annihilation of the American expedition. The shifting of the A-GO battlefield from the Palaus northward also forced Ozawa to steam a greater distance, pausing en route to refuel at sea. Yet, an American attack on the Marianas was not unexpected. A-GO could succeed, provided the Saipan garrison held firm and the 500 land-based planes promised to augment Ozawa’s carrier squadrons actually arrived in the Marianas.
When American battleships arrived off Saipan, General Obata was absent from his headquarters on a tour of inspection of the Palaus. When he realized that Saipan was in peril, Obata tried to return, but he got only as far as Guam. Tactical command passed to General Saito of the 43rd Division. The savage pounding by naval guns and carrier planes battered the defenders but did not destroy their will to resist. One Japanese admitted that the naval bombardment was “too terrible for words,” but he nevertheless was “pleased to think” that he would “die in true Samurai style.”25 A naval officer found momentary respite from his worries when he and a few of his men paused amid the ruins to bolster their spirits with five bottles of beer.26
On 14 June, in the midst of the holocaust, Admiral Nagumo issued a warning that “the enemy is at this moment en route to attack us.” He went on to predict that American amphibious forces would land no later than July.
After pointing out that the Marianas were the Japanese first line of defense, he directed each man to “mobilize his full powers to annihilate the enemy on the beach, to destroy his plan, and to hold our country’s ramparts.”27 Along the western beaches of Saipan, members of frontline units were better informed than the admiral, for they could see the buoys which were being set out to aid in controlling the next day’s assault.
The Saipan garrison had suffered from the preliminary bombardment, but the defenders were willing to fight. If humanly possible, they would defeat the Marines on the beaches. In the meantime, Ozawa’s ships were beginning their voyage toward the Marianas. The portion of A-GO that called for aerial surface, and submarine attacks on the advancing American convoy had already gone awry. Possibly, the attackers could be wiped out before a beachhead was established. If not, merely by holding for a comparatively brief time, Saito’s men might nevertheless set the stage for a decisive sea battle.