World War Two: Gilberts and Marshalls (1); Pacific Objective’s 1943-44

In November 1943 American forces successfully invaded the Gilbert Islands, which the Japanese had wrested from British control shortly after the attack on Pearl Harbor almost two years earlier. Thus the United States initiated the great westward drive across the Central Pacific that would eventually bring Allied forces to the very doorstep of the Japanese homeland. This drive would constitute the northern or upper part of a two-pronged movement against the heart of Japanese military and economic power in the Pacific.

The lower prong would be represented by General Douglas MacArthur’s steady progress up the Solomon Islands, up the northern coast of New Guinea, and into the Philippine Islands. But it was to the Central Pacific route, westward from Hawaii through the myriad islands and atolls of Micronesia, that the American strategic planners had assigned the “main effort” in the war against Japan. Along this path U.S. naval, ground, and air forces under command of Admiral Chester W. Nimitz were to begin a series of amphibious assaults of size and scope unparalleled in the history of oceanic warfare.

Prewar Plans

There was nothing new in the idea that the United States would have to seize strategic island bases in the Central Pacific in the event of a war against Japan. Throughout the 1920’s and 1930’s strategic planners in Washington had prepared a series of plans, designated the ORANGE plans, to provide for that contingency. All of these chose the Central Pacific as the main avenue of approach for a decisive move against the prospective enemy. The first ORANGE plan, approved by the Joint Army and Navy Board in 1924, conceived of an offensive war against Japan that would be essentially naval in character.

By cutting the Japanese Empire’s sea routes, and by air and naval operations, Japan, it was believed, could be isolated. The plan further provided that troops from the continental United States would be assigned to seize and hold islands in the Central Pacific, including the Marshall group, and that large bodies of troops would be dispatched to reinforce the Philippines.

Between 1925 and 1938 this original ORANGE plan was revised many times. In the final revision it was decided that the Philippines could be defended by their peacetime garrison plus whatever other local forces were available, without reinforcements from the United States. But none of the changes affected one basic aspect of the plan—U.S. naval forces would move westward through the islands of the Central Pacific to establish naval dominance in the western waters of that ocean.

The ORANGE plans had been prepared on the assumption that only the United States and Japan would be at war. By 1941 this assumption was no longer valid. The emergence of the Rome-Berlin-Tokyo Axis, the American decision to support Great Britain in her struggle against Germany and Italy, and the growing realization that the United States was likely to become involved in war against the Axis caused American and British officials to prepare tentative plans for combined action.

The last American plan made before 7 December 1941 was prepared on the assumption that the United States and Britain would be allied and at war with a combination of enemy powers and was designated RAINBOW 5. Although never formally approved by President Franklin D. Roosevelt, it was the plan put into effect at the outbreak of war between the United States and the Axis Powers. In the belief that Germany was the major enemy and would have to be defeated first, RAINBOW 5 declared the Atlantic-European theater to be the main area of operations. In the Pacific and the Far East the Allies would assume a role primarily defensive, although limited naval offensive measures were to be undertaken at the earliest possible moment.

Specifically, the U.S. Army was to help defend the Hawaiian and the Philippine Islands, and to help hold the entrance to Manila Bay. The U.S. Navy’s role in the Pacific was naturally more extensive. The Navy was to conduct raids, defend such American bases as Wake, Guam, Midway, and Samoa, “prepare to capture” the Japanese Mandated Islands and establish a fleet base at Truk, maintain the line of communications between the United States and the Philippines, and establish naval superiority in the western Pacific. Thus, with the assignment to the U.S. Navy of the task of seizing the Japanese Mandated Islands, including Truk, the role of the Central Pacific in the forthcoming war was reaffirmed.

Pacific Organization and Early Strategy

The success of Japan’s offensive moves in late 1941 and the first months of 1942 did not completely invalidate all Pacific provisions of RAINBOW 5, but it did postpone any attempt to carry out the offensive provisions in the early part of 1942.

By May 1942 the Japanese had seriously weakened the U.S. Pacific Fleet, had seized the Philippines, Wake, Guam, and the Gilberts, had captured Malaya, Burma, and the Netherlands Indies, and had installed themselves in the Bismarck Archipelago-New Guinea-Solomon’s area. They held an enormous perimeter of bases that included the Kurils, the Marianas, Wake, the Marshalls, Rabaul in New Britain, the Netherlands Indies, and Malaya, with outposts in the Gilberts, the Solomon’s, and New Guinea. They apparently expected the United States to grow war-weary launching attacks against these strong positions, and to give up the fight and agree to a negotiated peace.

But by mid-1942 the Japanese had overreached themselves. Confident after their first successes, they decided to capture positions in the Aleutians, the Fijis, Samoa, New Caledonia, and Midway, enlarge their holdings in New Guinea, and then to expand the main perimeter to include the newly won bases as well as the Gilberts. Seizure of Port Moresby in New Guinea and of the Fijis, Samoa, and New Caledonia would have cut the line of communications between the United States and Australia. Thus isolated, Australia could not be used as a base for Allied counteroffensives.

Frustrated in their attempt to take Port Moresby by the Allied Coral Sea victory in early May 1942, the Japanese turned to Midway and the Aleutians and met with disaster. Although they did obtain footholds in the Aleutians, their effort against Midway was a costly failure. In the Battle of Midway, 3-4 June 1942, the U.S. Pacific Fleet destroyed four large aircraft carriers plus hundreds of planes and many of their best-trained pilots. Thus crippled, the Japanese Combined Fleet was no longer capable of offensive action. The time had come for the Allies to seize the initiative. The groundwork had already been laid since the U.S. Joint Chiefs of Staff (JCS), who had been assigned responsibility for the strategic direction of the war in the Pacific, had already organized the Pacific theater and undertaken measures to initiate at least limited offensives.

The Joint Chiefs on 30 March 1942, with the approval of President Roosevelt and the Allied governments concerned, had organized the Pacific theater into two great commands—the Southwest Pacific Area and the Pacific Ocean Areas.

 The Southwest Pacific Area, under General MacArthur, consisted principally of Australia, New Guinea, the Bismarck Archipelago, the Netherlands Indies, the Philippines, and adjacent waters. The Pacific Ocean Areas included nearly all the rest of the Pacific Ocean. It encompassed virtually everything south of the Bering Strait, west of continental United States, north of the South Pole, and east of the Southwest Pacific Area and China. The Pacific Ocean Areas was divided into three commands: the North Pacific, which stretched north of latitude 42° north; the South Pacific, which lay south of the equator and east of the Southwest Pacific; and the Central Pacific, lying between the equator and latitude 42° north. Major islands and groups in the Central Pacific were the Hawaiian Islands, Wake, part of the Gilberts, the Marshalls, the Caroline’s, the Marianas, the Bonins, the Ryukyus, Formosa, and the Japanese home islands.5

Commander in Chief, Pacific Ocean Areas, with headquarters at Pearl Harbor, was Admiral Nimitz, who concurrently served as Commander in Chief, U.S. Pacific Fleet. By the terms of his orders from the Joint Chiefs of Staff, Nimitz commanded virtually all Allied forces in his areas. He directly commanded the Central and North Pacific Areas, but according to his instructions he appointed a subordinate as Commander, South Pacific Area.

After October 1942 this post was held by Admiral William F. Halsey, Jr. Missions assigned Nimitz and MacArthur were practically the same. They were to hold bases essential to the security of the U.S.-Australia line of communications, support operations that would contain the Japanese, support the defense of North America, protect necessary sea and air communications, and prepare for major amphibious offensives.

The first offensive moves of the Allies in the Pacific were undertaken in accordance with the basic Allied strategy for the conduct of the war—Germany would be defeated first and, pending the defeat of the German forces, the Allies would defend in the Pacific. But it had long been agreed that the Commonwealth of Australia and the Dominion of New Zealand, valuable as integral economic and political units of the British Commonwealth of Nations and as bases for future operations, would not be allowed to fall to the enemy. It was therefore necessary that the Allies hold the British Pacific possessions and retain control of the vital lines of communications to them. In early 1942 a substantial number offerees were sent from the United States to Australia and the bases along the line of communications. Defense of that line was also a primary mission of the U.S. Pacific Fleet.

Thus, when that fleet thrashed the Japanese at Midway, the Joint Chiefs’ next move was clear. With the Japanese infiltrating southward from Rabaul through the Solomon’s and New Guinea toward the line of communications and Port Moresby, General George C. Marshall, Chief of Staff, U.S. Army, and Admiral Ernest J. King, Commander in Chief, U.S. Fleet, and Chief of Naval Operations, on 2 July 1942 ordered the South and Southwest Pacific forces to advance through the Solomon’s and New Guinea to seize Rabaul and remove the enemy threats. Forces of the two areas moved promptly to the attack, and in the lengthy Guadalcanal and Papua Campaigns, which dragged on until early 1943, succeeded in halting the enemy’s southward advance.

By February 1943 the armed forces of the two areas were still far from capturing Rabaul, but they had insured the safety of the line of communications between the United States and the British Pacific dominions. With the Japanese on the defensive, the supply lines fairly safe, and Allied air and surface strength on the increase, the Joint Chiefs of Staff could consider the possibility of further offensive operations in the Pacific, especially in the areas under Nimitz’ immediate command.

The Casablanca Conference

While the Guadalcanal and Papua Campaigns were slowly drawing to a close, American and British planners met once more to decide, among other things, a future course of operations for the Pacific theater. The meeting was convened in Casablanca, French Morocco, in January of 1943. In attendance were President Roosevelt with the U.S. Joint Chiefs of Staff and Prime Minister Winston S. Churchill accompanied by the British Chiefs of Staff.

At Casablanca, although the British and Americans were agreed on such larger issues as the necessity for beating Germany first, there were some points of disagreement that had to be settled before the Allied program for 1943 could be determined. The British were generally reluctant to go immediately as far in the Pacific as the Americans desired.

The position taken by the American representatives was that, having seized the the initiative from Japan the previous August at Guadalcanal, it would be unwise to relinquish it and allow the Japanese to dig in too strongly or to mount a counteroffensive. Throughout the conference they continually stressed the importance of keeping constant pressure on Japan. The British, on the other hand, expressed their opposition to greater efforts in the Pacific at that time. They reminded their American colleagues of the extreme importance of beating Germany first, and in that connection of giving substantial aid to the Soviet Union. The Japanese, they suggested, should be contained by limited offensives until Germany fell.

The most articulate spokesman for the American position was Admiral King, who introduced the question of a Central Pacific offensive to the Combined Chiefs in the afternoon of 14 January. He began his discussion with an analysis of the strategic situation in the Pacific, where, he declared; the Allies were engaging the enemy on four fronts: the Alaska-Aleutians area, the Hawaii-Midway line, the South and Southwest Pacific Areas, and the China-Burma-India theater. After pointing out that the object of the Guadalcanal and Papuan operations was to secure the approaches to northeast Australia, and that Rabaul was the key to the situation there, he brought forward the problem of where to go after Rabaul was captured by the Allies.

The Philippine Islands, King advocated should certainly be a major objective, although he was not prepared at that time to rule out completely the possibility of driving through the Aleutians against the Japanese home islands. As between the East Indies and the Philippines, the latter was preferable since an attack on the Indies would be a frontal assault against a strong position, whereas the Philippines could be taken on the flank. Although King did not make the point explicitly, implicit in his analysis was the fact that seizure of the Philippines would cut off Japan from the vast riches of the Indies, especially oil, since the Philippines squarely blocked the sea routes between Japan and the Indies.

With the Philippines as a major objective, King argued, the next problem was the selection of a route of approach. He did not definitely commit himself on that point, though from his analysis it appears that he favored the Central Pacific. For years, he observed, the Naval War College had been studying the question of how to recapture the Philippines in the event they were taken by the enemy. Three routes of approach had been considered: an approach from the north to Luzon via the Aleutians; a southern route that was outflanked by enemy bases; and a direct route through the Central Pacific. The direct thrust, King declared, would necessitate “establishing a base in the northwestern Marshalls and then proceeding to Truk and the Marianas.” Later in the meeting he spoke strongly in favor of taking Truk and the Marianas. Both Admiral King and General Marshall re-emphasized the importance of keeping the Japanese under pressure by retaining the initiative, for, as King warned, there was always the danger that the Japanese might mass their remaining aircraft carriers for another great strike at either Midway or Samoa.

Three days later the American representatives at Casablanca submitted a more detailed proposal for immediate operations in the Pacific. Again arguing that it was essential that the Japanese be kept under “continual pressure sufficient in power and extent to absorb the disposable Japanese military effort,” they proposed that the following steps be taken:

  1. Seizure and consolidation of positions in the Solomon’s and in eastern New Guinea up to the Huon Peninsula, and of the New Britain-New Ireland area;
  2. Seizure of Kiska and Agattu in the Aleutians;
  3. Seizure of the Gilberts, Marshalls, and Caroline’s (including Truk) after the capture of Rabaul;
  4. Occupation of New Guinea as far as the Dutch border as an extension of the Truk operation; and
  5. Operations in Burma to keep China in the war and to intensify attacks by China-based planes against shipping.

Increases in Allied forces for the Pacific and Burma in 1943 would partly depend on what the Japanese did, but the reinforcements were planned: 250,000 air and ground troops, 500 planes, the larger portion of new U.S. warships, 1,250,000 tons of shipping, and reinforcements to the British Eastern Fleet for Burma.

Once more the British objected on the ground that Pacific operations might divert enough Allied strength to jeopardize the fight against Germany. Again both King and Marshall rose to defend the American position. To the British suggestion that the Allies confine their Pacific operations in 1943 to Rabaul and Burma alone, King replied that there were resources available to include the Marshalls as well. The month of May might find Rabaul in Allied hands, he argued, and since the Burma campaign would not begin until November, combat forces would remain idle in the interim unless they could be re-employed in the Marshalls. General Marshall was able to allay the British worries that Pacific offensives would cut into operations against Germany by proposing that the Gilberts-Marshalls-Caroline’s invasions be undertaken “with the resources available in the theater.” The British finally assented, and there were no more disagreements at Casablanca over Pacific strategy.

Thus, for their Pacific program for 1943, the Allies decided to “make the Aleutians as secure as may be,” to advance northwest from Samoa to protect the line of communications to Australia, and to mount diversionary operations against the Malay Barrier. They decided to advance directly west “as practicable” through the Central Pacific toward the line Truk-Guam, particularly against the Marshall Islands, in conjunction with operations against Rabaul, whose capture in 1943 was practically taken for granted. The advance through the Central Pacific would not be allowed to prejudice the recapture of Burma, nor would there by any northward advance from Rabaul toward Truk and Guam unless sufficient forces were available to complete the task and follow up.

As far as Pacific strategy was concerned, the U.S. Joint Chiefs of Staff had accomplished much at Casablanca. They had expounded in some detail the significance of Pacific operations to their British colleagues, and had secured approval of at least a start on the drive across the Central Pacific in 1943. The possibility of beginning the advance was of course closely connected with MacArthur’s and Halsey’s operations against Rabaul.

MacArthur’s Strategic Plans

At his headquarters in Brisbane, General MacArthur had been preparing for the recapture of Rabaul for some time, and by February 1943 had completed a detailed, comprehensive plan known as ELKTON. In addition, he and his staff were considering ways and means to accomplish the ultimate defeat of Japan. Looking far into the future, they concluded that the recapture of Rabaul would gain “important, but not decisive advantages” that would help future operations but would not adversely affect Japan’s war economy. In order to strike a great blow at the enemy’s capacity to wage war, MacArthur and his planners reasoned, Japan should be cut off from the Netherlands Indies with its great quantities of oil, tin, and rubber. If the Allies seized the Philippines and developed air and naval bases there, Japan could be denied access to the Indies. Thus far MacArthur’s conclusions agreed with those expressed by the U.S. Chiefs of Staff at Casablanca. But there was one major difference—the route of approach.

Whereas the Joint Chiefs had clearly intimated that the Philippines were to be approached through the Central Pacific, MacArthur concluded that a drive through the Marshalls and Caroline’s would have to be made without land-based air support, would be slow, would cost heavily in naval power and shipping, and would “require a re-orientation of front.” Since according to his reasoning the Central Pacific route was unwise, MacArthur desired that after he and Halsey had captured Rabaul, Southwest Pacific forces should advance west along the north coast of New Guinea and thence into Mindanao in the southern Philippines. Neutralization of the Palaus and seizure or neutralization of various islands in the Banda and Arafura Seas would protect the flanks of the advance. This long-range plan prepared by General MacArthur’s headquarters was designated RENO.

 In March 1943 representatives of the Central, South, and Southwest Pacific Areas convened in Washington to meet with the Joint Chiefs and Joint Staff Planners in a series of sessions known as the Pacific Military Conference. This conference paid only slight attention to the Central Pacific; its primary purpose was to decide what should be the next immediate steps in the South and Southwest Pacific theaters. The Joint Chiefs of Staff were not at this time apprised of MacArthur’s RENO plan, but they were given the full details of ELKTON.

 ELKTON contemplated a drive against Rabaul along two axes—through New Guinea and New Britain on the west and through the Solomon’s to New Ireland on the east—to culminate in a converging assault on Rabaul. But to execute ELKTON would have required 22 2/3 divisions and 45 groups of aircraft. The South and Southwest Pacific Areas together had a total of only 15 2/3 trained divisions and less than half enough aircraft. Some reinforcements could be provided, but the everlasting scarcity of troop transports and cargo ships prevented reinforcement on anything like the scale required by ELKTON. As a result, the Joint Chiefs decided not to try to take Rabaul in 1943. Cutting the objectives for 1943 in half, they ordered MacArthur and Halsey to take Woodlark Island and Kiriwina (Trobriand Islands) in the Solomon Sea, to seize the Lae-Salamaua-Finschhafen-Madang area of New Guinea, to capture western New Britain, and to drive through the Solomon’s to southern Bougainville.[NOTE GM-1616A]

[NOTE GM1-14: GHQ SWPA, ELKTON Plan for the Seizure and Occupation of the New Britain-New Ireland-New Guinea Area, 12 and 28 Feb 43 versions. A copy of the 12 February ELKTON is in OCMH files; a copy of the 28 February version is in G-3 files. For a more detailed treatment, see John Miller, jr., CARTWHEEL: The Reduction of Rabaul, a forthcoming volume in this series.]

[NOTE GM-1616A: GHQ SWPA, ELKTON Plan for the Seizure and Occupation of the New Britain-New Ireland-New Guinea Area, 28 Feb 43; Notes on Pacific Conf Held in March 1943, DRB AGO; JCS 238/5/D, 28 Mar 43, Directive: Plan for Opns for Seizure of the Solomon Islands-New Guinea-New Britain-New Ireland Area. In the end, Rabaul was never assaulted, but was neutralized by air action. For a fuller discussion of these and related points see Miller, CARTWHEEL.]

 Thus, the Pacific Military Conference of March settled for the time being the immediate future in MacArthur’s and Halsey’s theaters of operation. By curtailing the list of objectives to be captured in 1943, the conference also indirectly gave impetus to the Central Pacific drive since any addition to the total shipping, manpower, and equipment that might be made available to the Pacific in the future would not have to be sent to bolster the capture of Rabaul. Instead, it could be assigned to Nimitz’ Central Pacific theater. It remained for the Combined Chiefs of Staff to come to a final decision at their next meeting in respect to forthcoming operations in the Central Pacific and to determine which of the two theaters, MacArthur’s or Nimitz’, should be allocated priority in the drive against Japan.

The Washington Conference and the Strategic Plan for the Defeat of Japan

In May 1943 President Roosevelt and the Joint Chiefs of Staff met once more with Prime Minister Churchill and the British Chiefs of Staff, this time in Washington. The purpose of the Washington conference, which is generally known by its code name TRIDENT, was to re-examine Allied strategy for 1943 in the light of changes in the situation since the meeting at Casablanca. Little had developed in the Pacific since early February, and the conference concerned itself primarily with the European bomber offensive, the cross-Channel attack, possible operations after the seizure of Sicily, and the Burma-China-India theater. But the conference was called upon to consider a tentative plan for the war in the Pacific drawn up after Casablanca by the highest American strategists.

This plan, prepared by the U.S. Joint Chiefs of Staff and their subordinate committees and submitted to the Washington conference on 20 May 1943, was entitled “The Strategic Plan for the Defeat of Japan.”Strategic Plan” was actually a misnomer. It was not a plan according to strict military definition, for it gave no estimates of enemy strength and dispositions, did not mention the types and numbers of Allied forces that would be required to accomplish the missions it described, said nothing about command or commanders, and did not establish time schedules. Nevertheless, although more of a set of ideas than a plan, the “Strategic Plan” became the cornerstone of Pacific strategy for the remainder of 1943 and for 1944. Furthermore, it diverged widely from MacArthur’s strategic concepts as expressed in RENO.

The plan as it stood in May 1943 involved operations by China, Great Britain, and the United States. It also apparently encompassed action by the Pacific dominions of the British Commonwealth of Nations, although these were not mentioned by name.

The ultimate objective of all operations was naturally the unconditional surrender of Japan. It was then thought that securing unconditional surrender might require an Allied invasion of the Japanese home islands, although the U.S. Chiefs of Staff and their subordinates agreed that control of the sea, especially of the western Pacific, might bring about unconditional surrender without invasion, and even without an air offensive. If invasion proved necessary, it could not be successful unless the Japanese will to resist had been seriously weakened.

Undermining the enemy’s powers of resistance and his desire to keep fighting by a large, sustained air offensive against the home islands was regarded as the best method. The possibility of employing air bases in the Kuril Islands, Formosa, and Siberia to mount the offensive was discussed, but it was agreed that China offered the best sites. (The Marianas were not mentioned as a possible base for B-29’s, whose capabilities had been briefly discussed at Casablanca) China would thus have to be maintained, and United States and British forces would need to fight their way to China in order to secure a good port, preferably Hong Kong.

The two Allies would, according to the plan, get to China by three general routes: through Burma; through the Strait of Malacca and the South China Sea to Hong Kong from the west; and from the east across the Pacific and through the Celebes Sea to Hong Kong. The British, assisted by the Americans and Chinese, would recapture Burma, and would make the drive through the Strait of Malacca to Hong Kong by a series of amphibious operations. The Chinese would help capture Hong Kong and with American aid would seize and defend the necessary air base sites. Meanwhile, United States forces would be driving through the Celebes Sea to Hong Kong. Then China, Great Britain, the United States, and apparently the Pacific dominions would join forces in a grand air bombardment of Japan. Nothing was said about the invasion of Japan beyond the statement that it might be necessary. Although exact timing was not discussed, it was then generally thought that the final advances would not be undertaken before the fall of Germany, and might last until 1948.

The next problem dealt with by the plan was that of the selection of the route and methods by which U.S. forces would approach Hong Kong from the east. Here was one of the basic strategic decisions of the Pacific war. United States forces, it was decided, were to advance westward from Pearl Harbor through the Central Pacific, and through the South and Southwest Pacific Areas to open a line of communications to the Celebes Sea, recapture the Philippine Islands, secure control of the northern part of the South China Sea, and join in the descent upon Hong Kong. The main effort in the westward advance would be made in the Central Pacific, a subsidiary effort through the South and Southwest Pacific. This choice of the Central Pacific as the most advantageous route of advance was dictated by several considerations. It was much shorter and less roundabout than the southern route and would not require as many ships, troops, and supplies.

It was far more healthful than the pest-ridden jungles of the Solomon’s and New Guinea. Through the Central Pacific, the Allies could strike the enemy’s most vulnerable flank and isolate Japan from her overseas empire. Furthermore, if Allied fleets destroyed or contained the enemy fleet, they could then strike directly from the Pacific against the Japanese home islands, without relying exclusively on aerial bombardment from fields in China.

The Japanese could deploy only limited air and ground forces in the islands and atolls of the Central Pacific, whereas on the southern route only the availability of troops, planes, and ships would limit the size of the Japanese forces. The Allies, on the other hand, were under no such handicap because of their superiority in carrier-based air power. In the absence of land-based aircraft, carrier-based planes could support amphibious operations against island fortresses.

A successful drive through the Central Pacific would outflank the Japanese in New Guinea, whereas operations along the northern New Guinea coast would neither eject them from nor outflank them in the Central Pacific, and the Japanese would retain relative freedom of naval maneuver. And, as Admiral King had pointed out at Casablanca, an Allied drive exclusively along the southern route would expose flanks and rear to enemy attacks. Whereas an attack through New Guinea into the Philippines or the Indies would be a head-on push against large islands containing positions closely arranged in depth, one directed through the Central Pacific would strike at vulnerable positions separated from one another by vast ocean reaches, and thus not quite so well placed to support one another. Seizure of the Marshalls and Caroline’s would give the Allies control of much of the Pacific and place them in position to isolate Japan from the Philippines-Indies salient, perhaps by the seizure of Formosa. Further, the great American naval shipbuilding program would be largely wasted if the southern route were used, and certainly the U.S. Pacific Fleet could best be used in long-range offensives.

But if all these factors favored the Central Pacific as the area where the “main effort” against Japan should be launched, other considerations argued for continuing the South-Southwest drive at least as a secondary effort in support of the principal offensive. In the first place, it was believed that Australia would doubtless object to a redirection of all offensive effort to the Central Pacific. Besides, the oil fields of the Vogelkop Peninsula of New Guinea, then in Japanese hands, might be of some use to the Allies. Furthermore, Allied forces in the South and Southwest Pacific Areas were already in close contact with the Japanese, and shifting them all to the Central Pacific would waste time and shipping. Finally, and most important, was the fact that twin drives along the central and southern axes would provide more opportunities for mutual support, and by preventing the Japanese from being able to guess the time and place of forthcoming advances would keep them strategically off balance. For these reasons, then, American strategic planners decided to make the twin drives, with the main effort through the Central Pacific.

On 20 May the “Strategic Plan for the Defeat of Japan” was submitted to the Combined Chiefs of Staff. It was accepted as a “basis for combined study and elaboration of future plans.” Next day Admiral King spoke to the Combined Chiefs at some length to explain the American proposals. He reverted to many of the statements he and Marshall had made at Casablanca regarding routes across the Pacific, the importance of the various Allied lines of communications, and the necessity for maintaining constant pressure on the Japanese communication lines and recapturing the Philippines. In pursuit of these goals, Rabaul, Truk, and the Marianas were important intermediate objectives. The Marianas, which King stated were an important base on the Japanese lines of communications, he regarded as a key to success.

Two days later the Combined Chiefs of Staff approved a lengthy paper containing the U.S. Joint Chiefs’ proposals for Allied objectives in the Pacific and Far East in 1943 and 1944. This paper, based on the “Strategic Plan,” repeated previous arguments and provided estimates of forces required and forces actually available for particular operations.

Offensives in 1943 and 1944 should aim at the following:

  1. Conduct of air operations in and from China;
  2. Conduct of operations in Burma designed to increase the movement of supplies to China;
  3. Ejection of the Japanese from the Aleutians;
  4. Seizure of the Marshalls and Caroline’s;
  5. Seizure of the Solomon’s, the Bismarck Archipelago, and enemy-held New Guinea; and
  6. Intensification of operations against the Japanese lines of communications.

It was estimated that capture of the Bismarck Archipelago, which would secure the line of communications to Australia and help provide access to the Celebes Sea, would require perhaps seven divisions of which five would be amphibious units. If Rabaul were effectively neutralized by air bombardment, perhaps only five—three amphibious—would be needed. Assuming that Allied forces could capture western New Britain and southern Bougainville by December 1943, the Joint Chiefs concluded that the Bismarck Archipelago operations would not be completed before April 1944.

Seizure of the Marshalls, it was agreed, was essential to an extension of the line of communications to the Celebes Sea, and would also shorten and secure the routes to Australia. From the Marshalls, land-based aircraft could help support naval surface operations against the enemy’s communication lines, and there was always the possibility that an Allied push into the Marshalls would force the Japanese fleet to come out fighting. The Marshalls operation would require two reinforced amphibious divisions, four heavy bombardment and two fighter groups of land-based planes, and aircraft from four standard and four auxiliary aircraft carriers, in addition to four battleships, three more auxiliary carriers, twelve cruisers, sixty-three destroyers, twenty-four attack transports, forty-four tank landing ships (LST’s), plus landing craft. Garrison forces would include one reinforced division, 10 defense battalions, 545 planes, and 18 motor torpedo boats. The entire operation, from the initial invasion to the time the assault troops were withdrawn and readied for the invasion of the Caroline’s, would last six and three-fourths months. Capture of the Caroline’s would be a much larger affair. Possession of this enormous string of atolls would help give the Allies control of the Central Pacific, provide them with a major fleet base at Truk, and put them in position to push on to the southwest or to threaten the Japanese archipelago directly. Truk and Ponape, as well as various other atolls, would have to be captured; air raids against Guam and Saipan in the Marianas would be necessary. It was agreed that the Caroline’s should be approached through the Marshalls even if Rabaul were in Allied hands.

No specific time limit was set, but the Combined Chiefs of Staff agreed that the proposed Caroline’s campaign would be lengthy. And it would require, they estimated, 3 reinforced amphibious divisions, 2 heavy bomber groups, 10 carriers of the Enterprise and Essex classes, 7 auxiliary carriers, 4 modern battleships, 9 old battleships, 31 cruisers, 108 destroyers, 20 submarines, 45 attack transports, 15 attack cargo ships, 6 LSD’s (landing ships, dock), 3 headquarters ships (AGC’s), and miscellaneous auxiliaries. To garrison the islands would take two reinforced divisions and three defense battalions, plus aircraft.

Controlling factors would include amphibious equipment and availability of divisions with amphibious training. There were then two Marine divisions (the 1st and 2nd, in the Southwest and South Pacific Areas, respectively) that were ready to go, with the 3rd Marine Division in the South Pacific supposed to be ready for combat by 15 July. The 4th Marine Division in California was expected to complete its training before the end of the year. Since transferring divisions from the South and Southwest Pacific to the Central Pacific would take many ships that were urgently needed elsewhere, it was agreed that two more Marine divisions and two more Army amphibious divisions were required in the Pacific.

As far as naval forces were concerned, the picture was bright. The huge fleet could be provided, the Combined Chiefs asserted, and they concluded that the forces listed would be sufficient to carry or simultaneous operations in the Central and South Pacific Areas in 1943 and 1944.

The final resolutions of the conference, as approved by President Roosevelt and Prime Minister Churchill, established the Allied objectives for the remainder of 1943 and part of 1944, and allotted certain forces for reaching those objectives. All decisions reached at Casablanca that did not square with the Washington resolutions were canceled. The Americans and British restated their determination to force the unconditional surrender of the Axis at the earliest possible date. They decided to “maintain and extend unremitting pressure” on Japan to reduce her war-making power and to gain new bases with the expectation that Britain, the United States, and all Allied Pacific powers (including the Soviet Union if possible) would direct all their resources to force the surrender of Japan soon after Germany’s defeat.

The program for the Pacific and Far East was ambitious and complicated. Using as a basis the U.S. “Strategic Plan for the Defeat of Japan,” the Combined Staff Planners were to prepare an “appreciation leading to a plan for the defeat of Japan,” including an estimate of the necessary forces. Recapture of Burma in 1943 was considered impossible, but preliminary operations were to be started, air operations intensified, and the flow of supplies to China augmented.

In the Pacific, the objectives recommended by the Joint Chiefs—ejection of the Japanese from the Aleutians, seizure of the Marshalls and Caroline’s, seizure of the Solomon’s, Bismarck Archipelago, and Japanese-held New Guinea, and intensification of operations against the Japanese lines of communication—were all accepted. Unlike Casablanca, the Washington decisions included estimates offerees required, concluding on the cheering note that the Allies had enough of everything, granted that the rate of losses, especially in shipping, did not markedly increase.

By 1 January 1944, according to existing plans, one Marine and three Army divisions would be in the Central Pacific; the South Pacific would have two Marine, five U.S. Army, and one New Zealand divisions; the Southwest Pacific, four U.S. Army infantry, one U.S. Army airborne, one Marine, and eleven Australian Army divisions, of which three would be available for offensive operations. According to the Joint Chiefs’ estimates of 12 May two more divisions were thus needed for the Marshalls, two more for the Caroline’s, and three additional for New Guinea.

Thus the Washington conference of May 1943, although not primarily concerned with Pacific strategy, made important decisions regarding the conduct of the Pacific war. By approving in a general way the “Strategic Plan for the Defeat of Japan,” it set the pattern of strategy for the duration of the war against Japan. By authorizing the drive through the Marshalls and Caroline’s and approving allocation of the required forces, it determined the course of Admiral Nimitz’ operations for about a year.

With the selection of the classic Central Pacific route, the Joint Chiefs now faced the tasks of deciding on exact objectives and of picking the precise units for the forthcoming drive across the Pacific. In May 1943, while the Washington conference was under way, naval forces from Nimitz’ command and the 7th Infantry Division from the Western Defense Command recaptured Attu. The Japanese evacuated Kiska shortly before the landing of a joint U.S.-Canadian force there in August. The Aleutians were thus free of Japanese.

SOURCE: Seizure of the Gilberts and Marshalls: BY; Philip A. Crowl, & Edmund G. Love

World War Two: Gilberts and Marshalls (2); Targets and Tactical Planning



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