While the marines and soldiers of the V Amphibious Corps were still pushing toward the east coast of Saipan, Admiral Spruance received news that was to prove even more significant than that of the capture of Aslito field. Beginning on 15 June, American submarines patrolling the waters east of the Philippine Islands sent in a series of reports on enemy ship movements that seemed to indicate strongly that the Japanese were massing a fleet and were sending it to the rescue of the beleaguered defenders of Saipan.
Spruance, like all other high-ranking U.S. naval commanders in the Pacific, had hoped that an invasion of the Marianas would bring the enemy fleet out fighting. That hope now seemed likely to be fulfilled. The Japanese Navy, like the American, had long been imbued with Alfred Thayer Mahan’s doctrine that the sine qua non of victory in naval warfare is the destruction of the enemy fleet. In their own national history, the Japanese had only to look back as far as 1905 for historical warrant for this assumption. In that year, Admiral Heigachiro Togo had met and almost annihilated the Russian Fleet at the Battle of Tsushima, thus paving the way to Japan’s victory in the Russo-Japanese War and a long-coveted place in the international sun.
In the early stages of World War II the Japanese sought to put this doctrine to test, but always fell short of complete success. In spite of the tremendous damage done to it at Pearl Harbor, the U.S. Fleet survived and recovered with remarkable rapidity. Important sea battles were won by the Japanese in the Solomons, but none of them were conclusive. At Midway the tables were turned when U.S. carrier planes repelled an attempted invasion and administered a sound drubbing to the Japanese naval forces supporting it.
By late 1943 the high command of the Imperial Navy felt that conditions were ripe for a decisive fleet engagement. Twice in the autumn of that year Admiral Mineichi Koga, Commander in Chief, Combined Fleet, sallied forth from Truk in an effort to engage the U.S. Central Pacific Fleet. Both times he failed to discover his adversary. In the end he retired to Truk and allowed most of his carrier air strength to be diverted to the Rabaul area, where two thirds of it was lost. In the spring of 1944, as American forces threatened to press farther into western Pacific waters, the Japanese prepared another plan, Operation A-GO, in the hope of forcing a major fleet engagement.
[N2-7-2 Information on Operation A-GO is derived from: Japanese Studies in World War II, 60 and 97; USSBS, Campaigns, pp. 213-72; USSBS, Interrogations, II, 316.]
On 3 May 1944 Admiral Toyoda, Koga’s successor as Commander in Chief, Combined Fleet, issued the general order for Operation A-GO. It was assumed that the next major thrust of the U.S. Fleet would be into waters around the Palaus, in the western Carolines, and that there it could be met and bested by the Japanese. Thought was given to the possibility that the Americans might move first against the Marianas rather than Palaus, but the consensus among high Japanese naval circles favored the latter alternative. Probably wishful thinking entered the picture here, for it was obviously to the advantage of the Japanese to concentrate their naval forces in the more southerly waters. The 1st Mobile Fleet, commanded by Admiral Jisaburo Ozawa, was soon to be moved to Tawi Tawi in the Sulu Archipelago, and it was to this force that major responsibility for carrying out Operation A-GO was assigned. The Japanese were already suffering a shortage of both fuel and tankers, and should Ozawa extend the range of his operations as far north as the Marianas he would take considerable logistical risks.
Before A-GO could be executed, an American thrust in another quarter caused Toyoda to change his plans. On 27 May General MacArthur’s forces invaded the island of Biak in the Geelvink Bay area of New Guinea and placed the Japanese admiral in a dilemma. If Biak were lost to the invaders, the success of A-GO could easily be jeopardized by American aircraft based on that island. On the other hand, to reinforce Biak would entail at least a temporary dispersion of forces, and of course the first principle upon which A-GO was based was that of concentration of force. Faced with this choice, the Japanese decided to accept the risks of dispersion and to dispatch some of their ships and planes to the Biak area in an effort to drive the Americans off. This decision was reflected in a new plan of operations known as KON.
[N2-7-3 Information concerning KON and its effects is derived from: Smith, Approach to the Philippines, Ch. XV; Samuel Eliot Morison, History of United States Naval Operations in World War II, Vol. VIII, New Guinea and the Marianas, March 1944-August 1944 (Boston, Little, Brown and Company, 1953), pp. 119-33]
Three times within eleven days Japanese naval forces sailed forth for Biak with troop reinforcements. The first of the expeditions turned back on 3 June, having lost the element of surprise on being sighted by American submarines and planes. The second was struck by B-25’s and suffered one destroyer sunk and three others damaged before the entire task force was chased away by American warships. The third, which included the super-battleships Yamato and Musashi, the light cruiser Noshiro, and six destroyers, all detached from the 1st Mobile Fleet, was abruptly called off on 12 June when Admiral Toyoda received definite word that Admiral Spruance’s forces were attacking the Marianas.
Thus, the American soldiers on Biak were saved from further naval harassment by the timely appearance of Central Pacific forces off the Marianas. By the same token, the invasion of Biak by Southwest Pacific forces was to prove a boon to Admiral Spruance, Japanese plans for A-GO relied heavily on the support of naval land-based planes of the 1st Air Fleet stationed in the Marianas, Carolines, and Palaus, but one third to one half of all these planes were sent to Sorong and other bases in western New Guinea in response to the invasion of Biak. There, large numbers of pilots fell prey to malaria, and most of the aircraft were lost either to U.S. action or to bad weather. By the time the U.S. Fifth Fleet showed up to meet the challenge of A-GO, the land-based aircraft available to Toyoda had been sizably reduced in number.
On 11 June the Japanese admiral received word of Mitscher’s carrier strike against Saipan and immediately suspended the KON operation, ordering the task force bound for Biak to join forces with the main body of Ozawa’s 1st Mobile Fleet. Ozawa himself sortied from Tawi Tawi two days later, and on the morning of the 15th Operation A-GO was activated. Contrary to earlier Japanese expectations, the Americans had chosen to attack the Marianas rather than the western Carolines. Hence the scene of the impending “decisive fleet engagement” could only lie somewhere in the Philippine Sea—that vast stretch of ocean between the Philippines and the Marianas.
On the evening of 15 June Ozawa’s fleet had completed its progress from Tawi Tawi up the Visayan Sea and through San Bernadino Strait into the Philippine Sea. On the next afternoon it was joined by the KON force that had been diverted from Biak. Both fleets were sighted by American submarines, and it was apparent that the Japanese were heading in a northeasterly direction toward the Marianas.
[N2-7-4 The following account of the Battle of the Philippine Sea is derived from CINCPACCINCPOA
Opns in POA—Jun 44, Annex A, Part VII; Morison, New Guinea and the Marianas, Chs. XIV-XVI.
The Philippine Sea was so named as the result of a recommendation made by Admiral Nimitz in 1944, at the time of operations against the Marianas. The name was officially approved by the U.S. Board on Geographic Names in March 1945. The Philippine Sea applies to that area limited on the north by Japan, on the east by the Bonins and the Marianas, on the south by the Carolines, and on the west by the Philippines, Formosa, and the Ryukyu Islands.]
Altogether, Ozawa had mustered 5 carriers, 4 light carriers, 5 battleships, 11 heavy cruisers, 2 light cruisers, 28 destroyers, and 430 carrier-based combat aircraft. He was outnumbered by the Americans in every respect except in heavy cruisers. Spruance had at his disposal 7 carriers, 8 light carriers, 7 battleships, 8 heavy cruisers, 13 light cruisers, 69 destroyers, and 891 carrier-based planes. The mammoth American fleet was divided into four carrier task groups under Admiral Mitscher, Commander, Task Force 58. Mitscher was in tactical command, but his major tactical decisions had to be approved by Spruance as Commander, Fifth Fleet.
By the morning of 18 June all four American carrier groups had rendezvoused and were steaming in a southwesterly direction toward the approaching enemy. Spruance had ordered: “Action against the enemy must be pushed vigorously by all hands to ensure complete destruction of his fleet,” but had added the precautionary note, “Task Force 58 must cover Saipan and our forces engaged in that operation.”
That night Admiral Mitscher learned the full meaning of this qualification when his superior ordered him to change course to the east and maintain it until daylight. Mitscher protested but was overruled. Admiral Spruance was fearful that Ozawa might attempt an end run under cover of darkness and put the Japanese fleet between him and Saipan. The Fifth Fleet commander was unwilling to jeopardize the landing operations even if it meant a delay in closing with the enemy fleet. Actually, no such end run was contemplated by the Japanese commander, but Spruance had no way of knowing that at the time.
On the morning of the 19th, after the American carriers had turned west again, Ozawa’s planes, which were lighter and less well armed and therefore capable of greater range than their American rivals, delivered the first blow. In four separate raids lasting for almost five hours Japanese planes roared over the horizon in a futile effort to knock out Mitscher’s mighty fleet. Out of all the American surface vessels present, only one was hit—the battleship South Dakota, which lost 27 men killed and 23 wounded, but was not seriously damaged. For the rest, the raids were broken up and the raiders destroyed or turned back by the combined might of American ships’ fire and planes, chiefly the latter. Later that afternoon American strikes on Guam and Rota, which had been ordered for the morning, were resumed. By evening the “Great Marianas Turkey Shoot” was over with disastrous results to the Japanese. Out of 430 carrier planes, Ozawa lost 330.
Some went down under the fire of American ships and planes; others were destroyed on Guam and Rota; and still others were counted as operational casualties. Against this, only twenty-four American planes were shot down and six lost operationally. The same day, two Japanese carriers, Shokaku and Taiho (Admiral Ozawa’s flagship) were sunk by American submarines operating well to the south of Mitscher’s fleet.
That night Ozawa changed course to the northwest hoping to put distance between himself and the American fleet and to allow himself opportunity to refuel. Mitscher held to a westerly course in the belief that it would bring him across the track of his enemy. However, he could not send out night air patrols because none of his carrier aircraft were equipped with search radar, and not until late the following afternoon was aerial contact finally made with the Japanese fleet, which was now heading in the general direction of Okinawa. Mitscher immediately launched a twilight air attack that succeeded in destroying about 65 of Ozawa’s remaining 100 aircraft, sinking the carrier Hiyo, hitting another carrier and a battleship, and damaging two fleet oilers to the extent that they had to be scuttled. American plane losses came to 100, mostly incurred through crashes when the returning planes tried to land on their carriers after dark. Personnel casualties were not so heavy, coming to only 49.
Thus ended the Battle of the Philippine Sea. Mitscher would have detached his battleships, cruisers, and destroyers to pursue and destroy the fleeing enemy, but Spruance refused to break up the fleet. It would have made no difference anyway since Ozawa was by now too far away to be overhauled.
Despite the escape of six carriers and their escorts, the Imperial Navy had suffered a severe blow—one from which it never recovered. In the opinion of Samuel Eliot Morison, the Battle of the Philippine Sea “decided the Marianas campaign by giving the United States Navy command of the surrounding waters and air. Thus, the Japanese land forces on Saipan, Tinian, and Guam were doomed, no matter how bravely and doggedly they fought.”
There can be no doubt of the decisive influence of the sea battle on the ultimate outcome of the land campaigns in the Marianas. On the other hand, the immediate effects were not altogether beneficial from the point of view of the troops fighting ashore on Saipan. On first getting word of the approach of the Japanese Fleet, Admiral Spruance had detached from Admiral Turner’s attack force five heavy cruisers, three light cruisers, and twenty-one destroyers to supplement Task Force 58.
This left Turner without adequate fire support for his transport shipping, which was still in the process of unloading at Saipan. Consequently, most of the transports retired well to the eastward of Saipan on the night of 17 June and remained away from the Saipan area until the Battle of the Philippine Sea was over. The withdrawal of these transports naturally interrupted unloading and imposed additional strains on the already overburdened logistical program on Saipan.
No aspect of an amphibious landing against a hostile shore presents more complex problems than that of transporting supplies from ship to shore and allocating them at the proper time and place and in the proper amounts to the troops that need them. Similarly, no phase of an amphibious operation is so likely to become disorganized and even disorderly. Ordinarily, the assault landing craft and vehicles move from ship to shore in scheduled wave formations and in a fairly methodical fashion. Once ashore the troops deploy and eventually move inland according to prearranged plan. Supplies, on the other hand, cannot move off the beach under their own power. More often than not they are dumped at the water’s edge in a haphazard fashion by landing craft whose naval crews are primarily interested in putting out to sea again. The supplies stay at the shore line until shore parties can segregate them in some order on the beaches or until mechanical transportation comes ashore to haul them in to inland dumps. To the casual observer at least, the pile up and congestion of supplies at the shore line during the first phase of a normal amphibious assault presents a picture of total chaos.
To be sure, in a well-conducted amphibious operation the chaos is often more apparent than real, but even under the best conditions the problem of ship-to-shore supply is a complicated one and not easy of solution. At Saipan it was further complicated by local circumstances, which were formidable, although not unique. On the first day unloading was hampered by heavy artillery and mortar fire on the beaches that did not cease altogether until three days later. Hydrographic conditions were unfavorable to a steady movement of supplies and equipment in to the beaches. The uncertain naval situation made it necessary for the transports to retire to seaward each of the first three nights. Finally, for the next five days and nights most of the transports stayed at sea awaiting the outcome of the Battle of the Philippine Sea.
Enemy harassment of the beaches and the unfavorable hydrographic conditions offshore were of course felt most seriously by the two Marine divisions during the first two days of the operation. Sporadically, enemy fire caused all unloading work to be suspended as shore parties took cover. The beaches on the flanks of the landing area were completely inaccessible to boats of any kind. LST’s and LCT’s could ground on the abutting reef, but supplies from that point to shore had either to be manhandled or transferred to LVT’s and DUKW’s. Some landing craft could reach shore at the interior beaches by way of the narrow channel off Charan Kanoa, but at low tide its use was restricted to those of the most shallow draft, and at all times it was congested because both assault divisions were using it.
Inevitably, too, along the six thousand yards of beach there was some mix-up of supplies in spite of the elaborate organization to supervise the unloading of the transports and the movement of supplies to the troop units to which they were allocated. In accordance with standard amphibious doctrine, this task was shared by naval beach parties and ground force shore parties. The beach parties supervised the unloading of the transports and the progress of landing craft and vehicles to the shore line. Also, they marked channels and controlled traffic in the lagoon. In command of these operations was a force master who had under him two transport group beachmasters, one for each Marine division, each of whom in turn commanded two transport division beachmasters, one for each assault regiment. All of these naval officers were landed as soon as satisfactory lateral communications had been established, and each was provided with a communication team of one officer, five radiomen, and five signalmen.
Paired with the naval beach-masters and working in close co-ordination with them were the Marine and Army shore party commanders whose job it was to control traffic on the beaches themselves, receive the supplies as they were landed, and distribute them to the appropriate troop units. Each Marine division was authorized a shore party of 98 officers and 2,781 enlisted men. The 2nd Marine Division based its shore party organization on the pioneer battalion of its engineer regiment. Nine teams were organized under three shore party group headquarters. The organization of the 4th Marine Division’s shore party differed somewhat in that two shore party groups were set up, each with three teams. These were drawn from personnel of the 121st Naval Construction Battalion as well as from the pioneer battalion of the division engineering regiment.
Each of the three Army regiments had its own shore party battalion—the 152nd Engineers for the 165th Infantry, the 34th Engineers for the 105th, and the 1341st Engineers of the 1165th Engineer Group for the 106th Infantry.
Notwithstanding this system of interlocking and parallel controls, the first two days of the operation frequently saw supplies of the 2nd Marine Division being dumped on the beaches of the 4th Division and vice versa. When the 27th Division began to land the situation rapidly deteriorated. On the night of 16 June the 165th Infantry commenced to come ashore over Blue Beach 1 in the zone of the 4th Marine Division. Next day the 105th Infantry followed. Few, if any, preliminary plans had been made by higher headquarters to cover the details of landing the reserve division, and the division itself, in its initial planning, had made no provision for a landing in this particular area. Hence, the process of getting the troops and supplies ashore inevitably became a makeshift proposition. Colonel Charles Ferris, Division G-4, set up an on-the-spot system of controls, but was unable to persuade either the Navy beachmaster or the senior shore party commander at corps headquarters to agree to routing cargo to any single beach or to order the transports’ boats to report to a single control craft in the channel so that an accurate record could be kept of items discharged. The result was that the 27th Division’s supplies were landed over several beaches, and the Army troops had to scramble and forage to get what they needed.
On 18 June all ships carrying troops and supplies of the 27th Division retired eastward of the island to await the outcome of the Battle of the Philippine Sea. To add to the division’s difficulties, the 152nd Engineers, which had been assigned as the shore party for the 165th Infantry, was detached and assigned to corps, leaving only the 34th Engineers to perform shore party functions for the two Army regiments that landed. By the morning of the 19th the supply situation within the division had become critical. True, there was enough food and water on hand for immediate needs, but only by dint of borrowing K rations from Marine dumps and capturing the water cisterns on Aslito field.
The quantities of Class II, III, and IV (organization equipment, fuel and lubricants, miscellaneous equipment) supplies on hand were almost negligible. Small arms ammunition would last four days, but there were only about 600 rounds of 155-mm. ammunition available for each battalion and 1,200 rounds per battalion of 105-mm. ammunition, most of the latter borrowed from the Marines. Of the division’s vehicles, there were on shore only three 2-1/2-ton cargo trucks, twenty-three 3/4-ton weapon carriers, and forty-nine DUKW’s. Not until 20 June did the ships carrying the troops of the 106th Regiment return to Saipan, and not until the 27th were the division’s supplies and equipment fully unloaded.
The 27th Division was not alone in suffering an interruption to the flow of its supplies and equipment because of the Battle of the Philippine Sea. The hasty withdrawal of the naval transports on the 18th made an orderly discharge of any cargo over the proper beaches impossible. Priorities were assigned to rations, ammunition, and fuels, and other items had to be neglected. Moreover, in order to dispatch the cargo ships with all possible speed out of the danger area, it was necessary to permit them to unload over the beach that was the handiest. Thus, it was impossible to prevent a division’s supplies from being scattered among all the dumps. The only advantage enjoyed by the two Marine divisions in this respect lay in the three full days they had had to unload their cargo before the general exodus of naval shipping, but this was at least partly offset by the fact that for most of the time their landing beaches were under fire.
Meanwhile, during the period when most of the transports were cruising east of Saipan, shore parties were furiously at work improving the beach approaches and eliminating obstacles to a more rapid delivery of supplies across the reef. Twelve pontoon sections had been hauled to Saipan lashed to the sides of LST’s, and others came later, side-carried by ships of the first garrison echelon. By 18 June naval Seabees had floated three of these and commenced construction of a causeway pier off Charan Kanoa, which was increased in length as fast as additional sections could be obtained from LST’s on their return from retirement to sea. Next day the 34th Engineer Battalion opened up Yellow Beach 3 just north of Agingan Point by blowing two channels through the reef to permit small boats to discharge on the shore during high tide. The battalion also rigged up a crane on an overhanging point off the beach to enable it to unload matériel directly from landing craft into trucks waiting on a level above the beach itself. On 21 June the 1341st Engineer Battalion removed all the mines from White Beach 1 below Agingan Point and prepared access roads from the beach. Naval underwater demolition teams searched for anti-boat mines and blew landing slips in the offshore reef for LST’s and LCT’s.
One factor that eased the 27th Division’s unloading problems was that a large percentage of its supplies had been palletized before embarkation from Oahu. Unlike the two Marine divisions, which were skeptical of the process, the 27th Division had responded enthusiastically to General Holland Smith’s administrative order that 25 to 50 percent of all supplies and two to five units of fire be palletized. In fact, the Army division had palletized almost 90 percent of all its supplies and had reason to be grateful for its own forehandedness. Securing the matériel to wooden pallets permitted a more rapid unloading of landing craft at the beaches, released working parties that otherwise would have been engaged in the arduous labor of transferring cargo from landing craft into trucks, and reduced the number of men at the landing beaches in positions exposed to enemy fire. In the opinion of Holland Smith, “These advantages were clearly manifest at Saipan when palletized supplies of the 27th Division were handled as against un-palletized supplies of the 2nd and 4th Marine Divisions.”
Not all of the logistical difficulties that beset the fighting troops were due to unloading difficulties. Some shortages can be traced back to the point of embarkation and are attributable to insufficient shipping. This was particularly true in the case of motor transportation. There was simply not enough space aboard the transports assigned to the operation to stow all of the vehicles of the three infantry divisions and of the XXIV Corps Artillery. General Smith’s headquarters cut the table of organization and equipment allowances, and his own allowances were reduced again because of inadequate shipping space. In the end, out of all motor transport vehicles allowed by corps, only 94 percent of the ambulances, 83 percent of the trucks, 71 percent of the trailers, and 75 percent of the tractors could be embarked from Oahu. Although these cuts were distributed more or less equally among all the units involved, the 27th Division suffered somewhat less than the others, being able to carry with it 86 percent of its trucks, 99 percent of its trailers, and 99 percent of its tractors. However, this advantage was more than offset when, after arrival on Saipan, corps headquarters commandeered thirty-three of the Army division’s 2-1/2-ton trucks and refused to return them even as late as 6 July.
As a partial compensation for the shortages in standard types of motor transportation, a substantial number of DUKW’s was provided for the Saipan operation more than had hitherto been used in the Central Pacific. All together, 185 of these vehicles were embarked. Each infantry division had a DUKW company attached, as did XXIV Corps Artillery. The DUKW’s initial function was to land the artillery. This had entailed some modification both of the DUKW’s bodies and of the 105-mm. howitzer wheels. After the landing phase, the amphibian trucks were used continually throughout the campaign, chiefly for hauling ammunition from shipboard or supply dumps to artillery emplacements and as prime movers for 105-mm. howitzers. In the opinion of General Holland Smith’s G-4 officer, Colonel Anderson, GSC, “the DUKW was the outstanding single type of equipment employed in this operation.”
Later, as the fight in the central and northern part of Saipan progressed, one other serious supply shortage manifested itself. The heavy demand for artillery support and close-in infantry support by 81-mm. and 60-mm. mortars created an unexpected drain on the mortar ammunition supply. Previous experience in the Central Pacific had seemed to indicate that a total of seven units of fire would be sufficient for Saipan, but this proved to be too low an estimate, and on the basis of experience in the Marianas ten units was recommended for future operations. The initial fault in not loading enough ammunition aboard the assault ships was compounded by the fact that resupply ships were frequently not vertically loaded, thus making it difficult for the troops to get their ammunition ashore when they needed it. Also, the first ammunition resupply ship was late in arriving in the area, and many of these vessels withdrew at night because of threatened air attacks, thus making a build-up of reserves impossible.
The extent to which these shortages and delays, avoidable and unavoidable, affected the course of the battle on Saipan cannot definitely be determined. The shortages and delays were real enough, but the fact that they were reported in such detail by supply officers and others might be taken to be as much in evidence of the wealth of matériel to which Americans in combat were accustomed as of any real privation suffered on Saipan. The records show no single instance wherein any infantry or artillery unit had to cease fire for want of ammunition or became completely immobilized for lack of transportation. On the other hand, it can be assumed that any defects in a supply system automatically impede the progress of ground troops. It is highly probable that had more supplies been on hand and had they reached the front lines in a more expeditious fashion, the combat troops would have been able to move against the enemy with greater force and speed.
Post landing Naval Gunfire Support On Saipan, as elsewhere in the island warfare typical of the Pacific, one of the most effective weapons in support of the infantry proved to be ships’ fire. Naval vessels ranging in size from LCI gunboats to old battleships, and mounting guns of calibers from 20-mm. to 14 inches, cruised the 27 1st Amphibian Truck Company for the 2nd Marine Division; 2nd Amphibian Truck Company for the 4th Marine Division; Provisional DUKW Company (from Quartermaster Company) for the 27th Division; 477th Amphibian Truck Company for XXIV Corps Artillery.
coasts of the island prepared at all times to support the troops on call, lay down preparatory fire, illuminate the night with star shells, and perform a host of other duties. True, the configuration and terrain of Saipan imposed some natural limitations on the fullest exploitation of this support. Naval guns have a flat trajectory and the mountains and hills of the volcanic island often masked fire from the sea. Also, the reefs fringing many parts of the island kept the larger vessels from approaching within optimum range for direct fire at some targets.
On the other hand, many of the enemy’s guns and installations were emplaced in defilade in valleys that ran perpendicular to the shore line on the east and west coasts, and against these naval gunfire could be particularly effective. The caves along the shore line offered ideal hiding places for enemy troops and were also ideal targets for ships firing from the sea, especially for the vessels of more shallow draft.
In general, two types of controls were set up to permit the co-ordination between troops and ships so necessary to efficient operations of this sort. For close support missions it was customary each day to assign a certain number of vessels to each infantry battalion in the assault—usually two or three destroyers. During the entire course of the operation 2 old battleships, 2 heavy cruisers, 3 light cruisers, and 39 destroyers delivered call fires at various times. Attached to each battalion was a shore fire control party consisting of naval and ground force personnel furnished by the 1st, 2nd, and 295th Joint Assault Signal Companies, which were attached, respectively, to the 4th Marine Division, the 2nd Marine Division, and the 27th Infantry Division. These parties were in direct radio communication with their supporting ships and from their positions on shore would request fire missions and spot the results.
This system of control was generally employed for two types of missions. First were the close support missions fired sometimes within fifty yards of friendly troops. Destroyers’ five-inch guns were usually used for this purpose, and the bulk of all five inch ammunition (139,691 rounds) was consumed in this fashion. How effective it was is doubtful.
Admiral Turner’s final opinion was, “Field Artillery is much better qualified for this type of fire by reason of its greater accuracy and smaller burst patterns.” The second type of mission usually controlled by shore fire control parties was night illumination. Star shells were fired on request of the infantrymen to prevent infiltration, to help stop counterattacks, and to keep enemy activity to their immediate front under surveillance. Unfortunately, there were not enough of these projectiles on hand to satisfy the wants of the troops, and after the first night a quota of six per hour per ship had to be imposed except during emergencies.
Except for these two types of missions, request for all other sorts of ships’ fire on ground targets originated from the naval gunfire officer of the Northern Troops and Landing Force. His headquarters was set up ashore near those of the corps air officer and the corps artillery officer and the three worked in close co-ordination so as to avoid duplication of effort and waste of ammunition.
Under the naval gunfire officer’s supervision, all deep support fire missions were arranged, including preparation fires, deliberate and methodical destruction fires, counterbattery, harassing, and interdiction fires, and fires on targets of opportunity. Since these missions were not controlled by shore fire control parties, it was considered necessary to fix definite safety limits and to specify safe lines of fire. Preparation fires were not brought closer than 1,500 yards from the nearest friendly troops. Deliberate and moderate destruction fires, fires on targets of opportunity, and counterbattery, harassing, and interdiction fires were usually confined to areas 2,500 yards from the front line. On the whole these various missions were executed far more effectively than were close support fires, and it was in this field that naval gunfire won its laurels at Saipan. Other chores ably performed by the support ships were the guarding of Saipan against amphibious reinforcements from Tinian, neutralization of the airfields at Marpi Point and Ushi Point, Tinian, and destruction of enemy cave positions along the seacoast that were inaccessible to anything but the 40-mm. fire of LCI gunboats.
The testimony of prisoners of war captured on Saipan leaves no doubt of the impression made on the Japanese by American naval gunfire. Major Takashi Hiragushi, 43rd Division intelligence officer, testified, “the most feared of . . . [American] weapons was the naval shelling which managed to reach the obscure mountain caves where . . . CP’s were located.”
A captured Japanese lieutenant declared that the greatest single factor in the American success was naval gunfire. When asked how he distinguished between naval gunfire and land-based artillery, he laughed and said that it was not difficult when one was on the receiving end. Everyone in the hills “holed up” and waited when a man-of-war started to fire. Other Japanese prisoners of war, when interrogated on the matter, were in almost unanimous agreement. Perhaps the highest testimonial of the efficacy of this particular weapon came from General Saito himself when he wrote on 27 June, “If there just were no naval gunfire, we feel with determination that we could fight it out with the enemy in a decisive battle.”
Close Air Support
Once the assault troops had landed on Saipan and established their beachhead, the role of aircraft for the remainder of the operation was twofold. First, and most important, it was to keep the battlefield isolated from the inroads of enemy air and surface craft. Second, it was to support the advance of the ground troops in somewhat the same manner as naval gunfire and artillery.
After the Battle of the Philippine Sea no serious threat of enemy air intervention remained, and except for occasional nuisance raids the troops on Saipan could enjoy virtual immunity from that quarter. Thereafter, the planes of Mitscher’s Task Force 58 were employed on occasional troop support missions, while Admiral Turner’s escort carriers provided the aircraft for combat air patrols and antisubmarine patrols. Once Aslito airfield was captured. He was mistakenly identified as Major Kiyoshi Yoshida, 31st Army intelligence officer and put into operation, these duties were shared by P-47’s of the 19th and 73rd Fighter Squadrons, Seventh Air Force.
Whether in deep support or close support, the planes assigned to assist the ground forces flew three types of missions—bombing, rocketing, and strafing. Of these, the first was the least effective in knocking out comparatively small targets such as gun installations. After the initial softening up of the landing beaches, bombing missions were ordinarily employed against enemy troop concentrations, supply dumps, and buildings. The first extensive use of aircraft rockets in the Central Pacific was on Saipan. The rockets proved to be the most valuable weapon for support aircraft, in spite of the fact that there was insufficient training in its use and that no delay fuzes were available. The most common technique for close support missions was strafing, which was not only effective against the enemy but safer for friendly troops.
Troop requests for close air support were radioed by air liaison parties attached to each regiment and battalion. The requests were filtered through division and corps headquarters, each of which had the opportunity of rejecting them before final decision was made by the Commander, Support Aircraft, Captain Richard F. Whitehead, USN, who was aboard Admiral Turner’s flagship. Once a strike was ordered, it would be controlled either by Captain Whitehead himself, by the support aircraft commander on Holland Smith’s stall, by the air co-ordinator (who was a group or squadron leader from one of the participating carriers and was on station over the island at all times during daylight hours), or by the flight leader assigned to the particular mission.
Air liaison parties on the ground had no direct radio communication with the planes and were therefore unable to coach the pilots into their targets. Targets were designated in a variety of ways. Sometimes the infantry marked them with white phosphorus mortar shells. At others, planes flew dummy runs and waited to execute their missions until battalion air liaison parties notified the Commander, Support Aircraft, who in turn notified the flight leader if the runs were made on the correct area. Fluorescent panels were used to mark the front lines of the troops.
The highly centralized system of close air support control used at Saipan had the advantage of reducing to a minimum the danger of duplication of missions and of planes bombing and strafing within friendly lines. On the other hand, it was time consuming to a degree that was highly unsatisfactory to the troops. The time lag between requests for and execution of an air strike was sometimes more than an hour and seldom less than a half hour.
One reason for the delay was the difficulty of co-ordinating air with the other supporting arms. No single co-ordinating agency had been established before the invasion of Saipan. This created no especially difficult problem when it came to coordinating air and naval gunfire, since by mutual agreement naval gunfire was lifted in certain areas when requested by the Commander, Support Aircraft, and air attacks were stopped on the request of firing ships. On the other hand, the co-ordination of air and artillery presented a more difficult problem because of the higher ordinates of artillery pieces, their rapid rate of fire, and the lack of central control for the four separate artillery units. For these and other reasons, close air support was the least satisfactory of the three supporting arms.
Artillery support was of course provided by the three divisions’ organic pieces, as well as by the twenty-four 155-mm. guns and twenty-four 155-mm. howitzers of XXIV Corps Artillery, which was commanded by General Harper. Corps artillery commenced to land and go into position on 18 June, and by 22 June all four battalions were ashore and firing. The two 155-mm. howitzer battalions and one of the gun battalions were emplaced 1,500 to 2,000 yards south of Charan Kanoa on the low, flat, plain adjacent to Yellow Beaches, while the other gun battalion was emplaced on the higher ground just southwest of Aslito airfield.
Initially, all battalions faced north on Saipan except for Battery B, 531st Field Artillery Battalion, which was positioned to fire on Tinian. On 27 June the front lines had advanced to an extent calling for a forward displacement of the heavy battalions of the corps, and by the 28th all had been displaced to positions northeast of Magicienne Bay. On 7 July the 225th Field Artillery Battalion displaced again, this time to the northeastern edge of Kagman Peninsula. In addition to supporting the troops on Saipan, XXIV Corps Artillery had the job of guarding the back door to Tinian. Observation posts overlooking the southern island were manned twenty-four hours a day, and various harassing and destructive missions were fired on Tinian airfields and other targets on that island throughout the Saipan operation.
For the most part corps artillery was assigned the job of delivering deep support fires for the advancing troops, and a minimum safety band of 1,500 yards in front of the infantry was established. The division’s batteries engaged in night harassing fires, preparation fires in advance of the daily infantry jump-offs, fires on targets of opportunity, and call fires at the request of the troops. On several occasions division artillery fired rolling barrages. Close liaison was maintained between corps and each division artillery headquarters by liaison officers numbering as many as three per division. A similar system was maintained by the divisions themselves. Each light artillery battalion had a command liaison officer with its supported infantry regiment, and usually the Marine and Army artillery units exchanged liaison officers to co-ordinate fires near division boundaries. Primary means of communication was by wire, although this was not altogether satisfactory because the large number of tracked vehicles used on Saipan made maintenance of wire lines difficult As a substitute, all corps liaison officers were provided with truck-mounted radios.
Altogether, the four artillery units were to fire about 291,500 rounds before the end of the battle for Saipan. Of these, 37,730 can be attributed to the corps artillery. In spite of this considerable volume of fire, there were certain limiting factors to the optimum employment of artillery. Chief among these was terrain.
After the major portion of southern Saipan had been secured and the main American attack reoriented to the north, General Holland Smith disposed almost all of his field artillery to support the northward thrust. True, one battery of 155-mm. guns (later increased to three) was pointed to the south against Tinian, but all the remaining pieces were ordered to direct their fire against the Mount Tapotchau-Death Valley-Kagman Peninsula line and beyond.
The terrain in this central part of Saipan presented several problems to the gunners. XXIV Corps Artillery was assigned the general mission of deep support, which meant that most of its targets were located in the northern half of the island. Since Mount Tapotchau lay athwart the line of sight between ground observers and these targets, corps artillerymen had to rely entirely on air spotters. Six L-4 liaison planes were assigned for this purpose, and by the end of the operation each of the pilots and his accompanying air observer had put in approximately a hundred hours in the air over enemy territory.
A more serious problem faced the artillerymen of the three divisions whose mission was to fire in close support of the advancing troops. In the center of the island, just east of Mount Tapotchau, lay Death Valley, which ran north and south along the axis of the attack. Since most of the enemy’s guns and mortars in this area were sighted into the valley from the hills and cliffs on either side, they could not easily be reached by American artillery firing from the south. This was one reason for the slow progress made by infantrymen up the center corridor of the island. Furthermore, since the troops on the right and left pushed on more rapidly than those in the center, the front line became more and more bent back in the middle. The unevenness of the line made the adjustment of artillery fire all the more difficult Nevertheless, in spite of the fact that Saipan was far from an artilleryman’s paradise, the main body of Holland Smith’s troops during the attack to the north did at least have continuous artillery support. Not so those troops of the 27th Division that were left to clean out the Japanese who were holed up on Nafutan Point, the southeastern tip of the island. Except for tanks, naval gunfire, and, later, antiaircraft guns, the infantrymen assigned to this mission would have to depend entirely on their own weapons.
SOURCE: Campaign in the Marianas; BY: Philip A. Crowl (United States Army Center of Military History)