With the fighting on Eniwetok Atoll ended, U.S. forces in the Central Pacific were now free to consolidate the gains achieved by the capture of the three key positions in the Marshalls group. Three tasks remained before them. First, a host of undefended and lightly defended atolls and islands in the area had to be occupied. Secondly, air and naval bases had to be constructed to support the continued drive across the Central Pacific. Finally, the bypassed strongholds of Wotje, Mille, Jaluit, Maloelap, and Truk had to be kept under constant aerial bombardment to assure their neutralization.
Mop-up in the Marshalls
The job of occupying the various atolls and islands that the Japanese had chosen not to fortify fell largely to the 22nd Marine Regimental Combat Team, with a slight assist from the 111th Infantry Regiment. First to be occupied were the atolls of Wotho, Ujae, and Lae, lying immediately to the westward of Kwajalein. A detachment of about 350 marines from the 1st Battalion, 22nd Marines, accompanied by eight amphibian tractors, all loaded aboard an LST, landed unopposed on Wotho Atoll on 8 March and subsequently encountered twelve Japanese, the crew of a plane that had recently crash landed on the reef. All twelve committed suicide. Two days later the same force landed without opposition on Ujae, where it discovered six enemy operators of a weather station that had previously been bombed out by American planes. Five of the Japanese committed suicide; the sixth was taken prisoner. On 13 March a landing was made on Lae Atoll. No Japanese were on the island and the natives reported that none had ever been there. The same proved to be true of Lib Island southwest of Lae.
Next to fall under American control were a number of atolls lying southeast of Kwajalein. The job of occupying these was assigned to two groups of about 325 troops each from the 3rd Battalion, 22nd Marines, to which were attached seven amphibian tractors, all loaded on an LST. Both groups of this force proceeded in company to Ailinglapalap Atoll for the first phase of their operation. Before any landing in force was attempted, a native was picked up who revealed that the crews of two Japanese picket boats, numbering about forty men and equipped with four machine guns and numerous rifles, were on the main island of the atoll. On the night of 20 March and the following morning, the entire force of marines, numbering about 650, was landed without opposition. The Japanese were discovered drawn up in a prepared position, which was successfully assaulted. Thirty-seven of the enemy were killed, two taken prisoners and two or three escaped. The marines suffered three wounded. The escaped enemy were pursued around the island for a while, but the hunt was finally abandoned as futile and the marines returned to their LST to proceed to the next objective. One group went on to Namu Atoll, where it landed without opposition on 24 March. There, were found seven Japanese including one woman and four children, all of whom voluntarily surrendered. The second group proceeded to Namorik Atoll and landed on 26 March.
Natives reported one unarmed Japanese on the atoll but after extensive patrolling failed to locate him, the search was finally abandoned as a waste of time.
To a detachment from the 2nd Battalion, 22nd Marines, fell the task of securing the group of atolls and islands lying northeast of Kwajalein. Aerial reconnaissance and the interrogation of natives indicated that Ailinginae and Rongerik Atolls were uninhabited, so the marines were ordered not to investigate them unless it should be subsequently discovered that Japanese had fled to these places after other atolls in the northern group had been captured. The first of these to be visited was Bikini, later to become famed as the site of postwar U.S. experiments with the atomic bomb.
It was invaded on 28 March, and the five Japanese located on the atoll committed suicide. Three days later unopposed landings were made on Rongelap Atoll, where eleven Japanese were reported but none discovered. The same day a detachment from the 3rd Battalion, 22nd Marines, landed on Ailuk Atoll and discovered no enemy there. Within a few days the same force had invested the Mejit Islands and Likiep and Utirik Atolls, netting a small bag of enemy stragglers. Finally, late in April, Company I of the 111th Infantry Regiment completed the occupation of the lesser Marshalls by capturing Ujelang Atoll, which lies about 140 nautical miles southwest of Eniwetok. The landing was made without opposition on 22 April and eighteen Japanese were flushed out and killed. Thus ended the American occupation of the Marshall Islands with the exception of Wotje, Mille, Jaluit, and Maloelap, which were left to “wither on the vine” subject to constant harassment by American planes and ships.
Building the Marshalls Bases
Immediately after Majuro Atoll was occupied, naval Seabees went ashore on Dalap Island to commence construction of an airstrip.2 When this was completed in March, it measured 4,800 by 445 feet and was thereafter constantly in use for raids against Mille, Wotje, Maloelap, and Jaluit. A naval base was established on the atoll to support two Marine dive bomber squadrons, half of a Marine patrol squadron, and temporary staging for one Army fighter group flying out of Makin against the bypassed Marshalls. In addition, Majuro provided a fleet anchorage (without shore-based facilities), medical facilities for the fleet, and a loran transmitting station.
Repair ships and submarine and destroyer tenders, together with tankers and supply ships, rode at anchor in the lagoon to supply the needs of whatever elements of the fleet passed through. Majuro, along with Eniwetok and Kwajalein, was to serve as a primary staging base for the American forces when they attacked the Marianas from June through August of 1944.
On Roi-Namur the 121st Naval Construction Battalion went ashore on 5 February, only three days after the island was declared secured. A day later it was joined by the 109th Naval Construction Battalion, and Seabees set to work immediately repairing and enlarging the Japanese airstrip on Roi. Progress was temporarily interrupted on 13 February when a flight of enemy bombers launched a heavy attack against Roi, setting fire to a bomb dump.
Altogether the Seabees suffered 157 personnel casualties, and the 109th Battalion lost 75 percent of its material and 35 percent of its equipment. Nevertheless work continued, and on 15 May the field on Roi was commissioned, with a hundred planes based there. Long before the final commissioning of the field, it was in daily use as a base for strikes against Wotje, Jaluit, and Kusaie, and subsequently it became one of the primary bases for raids against Truk. In March the 74th and 107th Naval Construction Battalions went ashore on Kwajalein Island, where they rebuilt the Japanese runway into a 6,300-foot coral surfaced strip with two 80-foot taxiways and 102 hard stands for heavy bombers.
In addition, water-front facilities were developed to provide for minor fleet repairs, the Japanese pier reaching into the lagoon was restored, a 250-ton pontoon drydock was assembled, and a 2,000-ton floating dock was provided. On nearby Ebeye other Seabees developed a seaplane base, which was completed by April. Kwajalein Island was to become the primary base for Army bombers flying against Truk. On Eniwetok Atoll Seabees began repairs and construction work late in February. By 5 March the airstrip on Engebi was able to accommodate three Army medium bombers (B-25’s), which went into action against enemy shipping at Kusaie five days later.
By 20 March a 6,000-foot airstrip had been completed on Eniwetok Island as well. Parry Island was used as a small-boat repair base and a seaplane base, the ramp and facilities for servicing seaplanes being ready for use early in May. Eniwetok Atoll thereafter served as an advanced fleet anchorage without shore-based facilities, as well as an air base capable of handling two heavy seaplane patrol squadrons, two fighter squadrons, one half of a night fighter squadron, one scout bomber squadron, two heavy bomber squadrons, and one photographic squadron. From May through October 1944, Army squadrons staging through Eniwetok and Navy and Marine squadrons based there flew continuous sorties against Truk and Ponape. In addition, Navy bombers staging through Eniwetok delivered low level bombing and strafing attacks against Wake, and daily reconnaissance of Wake was conducted by seaplanes based on Parry.
Neutralizing the Bypassed Atolls
From February 1944 until the close of the war, that area of the middle Pacific containing the Gilberts, Marshalls, and eastern Caroline’s became virtually an American lake through which ships and troops passed freely with little danger of enemy interception. The reason, of course, was that the capture of key bases in the Marshalls and the establishment of airfields thereon made it possible for the superior American air arm to keep the atolls still remaining in Japanese hands under constant surveillance and bombardment. By the time of the capture of Kwajalein, Japanese aircraft in the eastern Marshalls (Mille, Wotje, Jaluit, and Maloelap) had been either completely destroyed by Army and Navy aircraft or evacuated.
Thereafter, the main effort of American aircraft was to prevent these bases from being reinforced and rehabilitated and to bomb out and starve out the enemy abandoned there. After mid-March, when the base at Majuro was completed, Army medium bombers flew regular flights out of Tarawa and Makin, bombed two of the bypassed islands, landed at Majuro for rearming and refueling, and then bombed the other two targets on the way home. At the same time ten fighter squadrons and two bomber squadrons of the 4th Marine Air Base Defense Wing at Kwajalein flew a steady series of sorties against the same islands. After June 1944, Marine flyers assumed sole responsibility for these targets.
In March two heavy bomber groups of the Seventh Army Air Force moved onto Kwajalein for the primary purpose of conducting bombing raids against Truk. In conjunction with planes of the Thirteenth Army Air Force based in the South Pacific, bombers of the Seventh, flying out of Kwajalein and staging through Eniwetok, kept Truk effectively neutralized from April 1944 until the end of the war.
Tactical and Strategic Consequences of the Marshalls Operation
Writing soon after the capture of the Marshalls, General Holland Smith reported, “Recommendations made and acted upon . . . as a result of the Gilberts offensive proved sound. In the attack of coral atolls, very few recommendations can be made to improve upon the basic techniques previously recommended and utilized in the Marshalls . . .” As a matter of fact, after the capture of Eniwetok it was found unnecessary to seize any more well-defended atolls in the Pacific. Thereafter, all major landing operations were conducted against larger island masses ranging in size from such small volcanic islands as Iwo Jima and Ie Shima to such comparatively large land masses as Luzon and New Guinea.
In the latter phases of the Pacific war, then, many new problems presented themselves on which the experience in either the Gilberts or the Marshalls had no particular bearing. Large bodies of troops of corps and army size had to be maneuvered over relatively vast areas of land. Campaigns were to be measured in months, not days. The burden of supply, transportation, and medical care and evacuation were correspondingly increased. Tactical aviation assumed a new role. On Luzon and again at Okinawa, fighter and bomber planes were to be used extensively in close support of ground troops that had penetrated far inland from their original beachheads.
Fleet tactics, too, underwent considerable revision. Continuous attrition of Japanese naval and air strength plus the mighty build-up of American naval power freed the U.S. Fleet from the cautious hit-and-run tactics it had been compelled to resort to as late as February 1944. For the most part thereafter, the fleets that struck succeeding objectives in conjunction with landing forces came prepared to stay at least until all serious ground resistance had been eliminated. In the Marianas, the Palaus, the Philippines, Iwo Jima, and, finally, Okinawa, the U.S. Fleet stayed close offshore of the land targets for prolonged periods of time, ready to render constant support to ground troops as they pressed forward toward their objectives. And this in spite of the growing menaces of the Japanese Kamikaze (suicide) Corps, which mounted steadily from October 1944 to May 1945.
Yet notwithstanding these changes the progress of the war in the Pacific was to bring about, one aspect of most of the subsequent campaigns remained basically unchanged—the technique of the amphibious landing. Insofar as this phase of Pacific warfare was concerned, Holland Smith’s generalization that “very few recommendations can be made to improve upon the basic techniques previously recommended and utilized in the Marshalls” proved quite valid. The techniques that had been perfected in the capture of tiny atolls in the Central Pacific proved applicable, and were in fact applied, with only minor variations in most of the subsequent island landings as U.S. and Allied forces worked their way closer and closer to the heart of the Japanese Empire.
In the Marshalls operations some important innovations were made in the techniques and equipment of American amphibious assault procedure. The amphibious headquarters ship, which had already seen action in the Mediterranean theater, was first introduced into the Pacific at Kwajalein, where it conclusively demonstrated its value. For the first time there also, infantry landing craft were equipped with both 40-mm. guns and rockets and were effectively employed to lay down a last-minute barrage just before the troops landed. Underwater demolition teams demonstrated their ability to swim close to shore into the very teeth of the enemy under the protective cover of naval fire. The DUKW saw its first action on any large scale at Kwajalein and proved its immense value as a cargo and artillery carrier. At Eniwetok naval star shells were for the first time extensively employed to illuminate areas behind friendly lines and thereby impose a serious check on the standard Japanese tactic of night infiltration.
With the conclusion of the Marshalls operation, the standard pattern of American amphibious landings was set and was thereafter followed with a high degree of consistency by U.S. forces whenever they attacked an enemy beachhead in the Pacific. A few new items of equipment and a few new techniques were to be evolved that would improve still further on this pattern, but they introduced no major changes.
After February 1944, standard procedure called for as heavy and as prolonged preliminary naval and aerial bombardment of the beachhead as conditions permitted. Where feasible, this was supplemented by the emplacement of land-based field artillery on islands near the main landing beaches before the principal landings were made. Underwater demolition teams searched the shore line and the shallow water offshore for obstacles and mines and detonated them where necessary. Just before the landings, a last-minute preparatory fire was delivered by shallow-draft vessels of various types firing a variety of missiles from 20-mm. shells up through 4.5-inch rockets. The assault troops, boated insofar as possible in amphibian tractors, landed in waves and pressed the attack forward, followed by waves of tanks, artillery, and supplies and equipment, which were carried in amphibian tractors, amphibian trucks, and landing craft and ships of all sorts and sizes. Naval and land-based aircraft kept the enemy under continuous pressure and naval ships, where possible, supplied close and deep support to the troops as they advanced forward.
Some of these elements of force were omitted in subsequent island landings in the Pacific, especially in the various amphibious operations on the New Guinea coast, where enemy opposition was relatively light and such a preponderant display of power was unnecessary. But most of the techniques were employed in the major landings and all of them were used with brilliant success at Tinian and Okinawa. By the close of the Marshalls campaign, the basic pattern for the Pacific style of amphibious assault was set and any subsequent deviations therefrom were minor.
Strategically speaking, the easy capture of main bases in the Marshalls, coupled with the successful raid on Truk, was of utmost significance in its influence on the course of the future conduct of the war in the Pacific. First, the combined operations against the Marshalls and Truk served to confirm and reinforce the opinions already held by the Joint Chiefs of Staff and other strategic planners that the Central Pacific drive offered the most profitable route by which Allied forces could deliver a death blow against the Japanese Empire. Second, the strike against Truk revealed that base to be far weaker than had originally been supposed by most American planners and led to the final decision to bypass it altogether.
Finally, the economy of force with which the Marshalls had been taken and the removal of Truk from the list of prospective targets made available to Admiral Nimitz a large body of trained troops that could now be employed to accelerate the Central Pacific drive to a far greater degree than had originally been planned. In the spring of 1943, the Joint Chiefs of Staff had decided that the main effort in the war against Japan should be made along the Central Pacific axis, with a simultaneous but subsidiary effort to be launched through the South and Southwest Pacific. This decision had been reached in spite of the strong recommendations by General MacArthur that his own theater be given paramount consideration in Pacific planning.
The quick victories in the Marshalls confirmed the original judgment of the Joint Chiefs and strengthened their resolution to continue the main pressure along the Central Pacific axis. Two questions, however, called for immediate solution. The first was whether to launch the next attack in Admiral Nimitz’s theater against the Marianas. The second was whether or not to bypass Truk, keeping it neutralized from the newly acquired bases in the Marshalls and letting it “wither on the vine.”
The feasibility of an attack against the Marianas had long been discussed and debated among members of the Joint Chiefs of Staff, their subordinate committees, andtheater staffs in the Southwest and Central Pacific. Admiral King had firmly declared that the capture of the Marianas was the “key to success” in the Pacific war, and he was supported in that opinion by the Army Air Forces representative on the Joint Chiefs of Staff, General Henry H. Arnold, who wanted the Marianas as bases for B-29 raids against the Japanese homeland.
In the meetings of the Combined Chiefs of Staff held in Cairo in November and December 1943, the King-Arnold argument was accepted by the Allied strategic planners. The advance westward through the Central Pacific, through the mandated islands to the Palaus, and north to the Marianas was approved. Again, it was stated that Central Pacific operations were to have priority over those of the Southwest Pacific.
On the basis of the Combined Chiefs’ decision, Admiral Nimitz had issued a tentative plan of operations on 13 January 1944, designated GRANITE. Initial landings in the Marshalls were to be undertaken on 31 January. Late in March a carrier strike against Truk was to be executed, and in May amphibious landings were to be made in the western Marshalls. Landings on Truk and Mortlock in the Caroline’s would be initiated on 1 August. If Truk were bypassed, the Palaus would be invaded instead on approximately the same date. Amphibious operations against the Marianas were to begin about 1 November.
The early successes in the Marshalls operation and the successful carrier raid against Truk of 17-18 February enabled Admiral Nimitz to step up this program considerably. He became more convinced than ever of the feasibility of bypassing Truk and so recommended to the Joint Chiefs of Staff. He advocated instead an invasion of the Marianas on 15 June, to be followed by the seizure of Ulithi Atoll, about 360 miles southwest of Guam; the capture of Yap Island, a Japanese air base 100 miles southwest of Ulithi; and the capture or neutralization of the Palaus, about 300 miles still farther to the southwest. Woleai, in the Caroline’s, 360 miles due south of Guam, should also be captured, he recommended, to assure the neutralization of Truk and to protect the lines of communication from the Marianas to Yap and Ulithi.
With these and other recommendations in hand, the Joint Chiefs of Staff issued on 12 March a new operational directive for action in the Pacific during 1944. General MacArthur was ordered to cancel the proposed Kavieng operation and complete the neutralization of Rabaul with the minimum of forces. Following the development of Manus Island in the Admiralties as an air and fleet base, he was to occupy Hollandia on or about 15 April and conduct operations along the New Guinea coast preparatory to an invasion of the Palaus and Mindanao, southernmost of the Philippines.
Admiral Nimitz was ordered to cancel his plans for seizing Truk and expedite the neutralization of Truk and other islands in that immediate area. Nimitz was also to conduct carrier strikes against the Marianas, the Palaus, the Caroline’s, and other profitable targets. The Marianas were to be invaded on 15 June 1944, after which Central Pacific forces were to move to the Palaus.
Thus, with the successful conclusion of the campaign in the Marshalls, it became possible to launch the drive against the Marianas at a far earlier date than had originally been anticipated. Truk was to be bypassed and kept neutralized by aircraft operating chiefly out of the newly seized Marshalls bases. These bases were also to be put to good use in staging fleet elements that would later be used not only against the Marianas but also against the Palaus and the Philippines themselves.
Most important, the early and quick capture of the Marshalls released a volume of manpower for early employment against the Marianas. Originally, Admiral Nimitz had allocated the task of seizing Eniwetok to the 2nd Marine Division and two regimental combat teams of the 27th Infantry Division. When it was found possible to employ the reserve force initially assigned to Kwajalein for this task, the 2nd Marine Division and the two regimental combat teams of the 27th Division were immediately set upon the task of training for the forthcoming Marianas campaign. The decision to bypass Truk freed still more ground forces for future operations.
In January 1944, Nimitz had earmarked three Marine divisions, two Army divisions, and an independent Marine regiment for the capture of Truk and adjacent atolls.10 Three of these divisions (the 2nd and 4th Marine Division and the 27th Infantry Division) were now free to be trained for employment in the invasion of Saipan. Two others, the 3rd Marine Division and the 77th Infantry Division, as well as the 22nd Marine Regiment, were to be used against Guam. With the quick termination of the capture of the main Japanese bases in the Marshall Islands, the drive of U.S. forces through the Central Pacific against Japan was greatly speeded up. Any previous doubt as to where would lie the “main effort” against the enemy was permanently dispelled. “Thus,” to quote Admiral Nimitz again, “we get on with the war.”
SOURCE: Seizure of the Gilberts and Marshalls: BY; Philip A. Crowl, & Edmund G. Love (United States Army Center of Military History)