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 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 2d 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.
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.
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.
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.
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 2d 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
1. Unless otherwise noted, the material in this chapter is derived from: TF 51 OpRpt; TF 56 OpRpt; TG 52.2 OpRpt; NTLF OpRpt; 2d MarDiv OpRpt Phase I, FORAGER (incl a six-part narrative, four-part SAR, and SplCmts), dtd 11Sep44, hereafter 2d MarDiv OpRpt; 4th MarDiv OpRpt; 27th InfDiv Op Rpt; CominCh, The Marianas; Crowl, The Marianas; Hoffman, Saipan; Morison, New Guinea and the Marianas. A complete file of CinCPac-CinCPOA and JICPOA translations is available from OAB, NHD.
2. LtGen Thomas E. Watson ltr to Dir Div PubInfo, dtd 9Jun49, quoted in Hoffman, Saipan, p. 31. No copy of this letter has been found.
3. The arming and employment of these mortar craft was a project jointly developed by Admiral Hill and the CinCPac gunnery staff. Their intended mission was "cruising back and forth along a lighted buoy line close to the beach between Charan-Kanoa and Garapan and maintaining a constant barrage on the road connecting those two points throughout the first two or three nights after the landing." Hill comments Saipan.
4. MajGen Louis R. Jones ltr to HistBr, HQMC, dtd 8Feb50, quoted in Hoffman, Saipan, p. 34. No copy of this letter has been found.
5. The concentration of such an armada was a tribute to Navy planners, for the movement toward Saipan coincided with or immediately followed landings at Biak in the Schouten Islands, the sailing of the convoy that would carry Southern Troops and Landing Force to Guam, and the invasion of France.
6. Hoffman, Saipan, p. 34n.
7. CinCPac-CinCPOA Item No. 10,238, Diary of Tokuzo Matsuya.
8. CinCPac-CinCPOA Item No. 11,405, Diary of an Unidentified Japanese NCO.
9. LtCol Joseph L. Stewart ltr to CMC, dtd 9Jan50, quoted in Hoffman, Saipan, p. 36. No copy of this letter has been found.
10. Adm Raymond A. Spruance ltr to CMC, dtd 17Jan50, quoted in Hoffman, Saipan, p. 37. No copy of this letter has been found.
11. Cdr Francis D. Fane and Don Moore, The Naked Warriors (New York: Appleton-Century-Crofts, Inc., 1956), p. 88.
12. Additional sources for this section include: CinCPac-CinCPOA Items Nos, 9,159, Organization of CenPac AreaFlt, n.d., 10,145, Thirty-first Army Stf, TransRpt, dtd 18Mar44, 10,638, O/B for Thirty-first Army, 1942-1944, n,d., 10,740, Location and Strength of Naval Land Units, c. Apr44; HqFEComd, MilHist See, Japanese Research Div, Monograph no. 45, Imperial General Headquarters Army Section, mid-1941--Aug45; HistSec, G-2, GHQ, FEComd, Japanese Studies in WW II Monograph no. 55, Central Pacific Operations Record, Apr-Nov44; Northern Marianas GruO A-4 (with maps), dtd 24May44 in 4th MarDiv RepTranslations made on Saipan, hereafter 4th MarDiv Translations.
13. On 10 April 1942, the 5th Base Force was reorganized and redesignated the 5th Special Base Force. Chief, WarHistOff, DefAgency of Japan, ltr to Head, HistBr, G-3, HQMC, dtd 9Mar63.
16. CinCPac-CinCPOA Item No. 12,058, Thirty-first Army Stf Diary, 25Feb44-31Mar44.
17. Japanese comments Saipan, op cit.
19. NTLF G-2 Rpt, p. 65, in NTLF OpRpt.
20. CofS, Thirty-first Ar, Rpt of Defenses of Various islands, dtd 31May44, in NTLF Translations of Captured Documents (FMFPac File, HistBr, HQMC ) .
21. Japanese Monograph No. 55, op. cit.
22. CinCPac-CinCPOA Items Nos. 12,250, Army and Navy AA, Dual Purpose, and Coastal DefBtrys on Saipan, n.d., 12,251, Order of Change of Location of Army AA Btrys on Saipan, dtd 10May44, and 12,252, Dispositions of Navy Dual Purpose and Coastal Def Btrys on Saipan and Tinian, dtd 15May44.
23. Crowl, The Marianas, p. 454. These revised figures will be used in preference to the estimates made by NTLF during the Saipan battle.
24. USSBS Interrogation, Adm Soemu Toyoda, IJN, II, p. 316.
25. CinCPac-CinCPOA Item No. 10,051, Extracts from the Diary of an Unidentified Soldier.
26. CinCPac-CinCPOA Translations and Interrogations, No. 29, Item B-1938, Diary of a Naval Officer, Jun-Jul44.
27. ComCenPacFlt memo, dtd 14Jun44, in NTLF Translations.