Operation Cartwheel

Bougainville

The General Plan

by James Miller, jr.

If ever a series of offensives was conducted according to plan, it was the extremely systematic Allied moves in the Pacific that started in 1943. At the time that Allied forces were fighting in New Guinea and New Georgia, the joint Chiefs were considering the wisdom of neutralizing Rabaul, and General MacArthur and Admiral Halsey were preparing for the invasion of Bougainville.

ELKTON III had initially provided that the southern Bougainville area (Buin and Faisi) was to be invaded during the fifth month after the beginning Of CARTWHEEL, simultaneously with the conquest of New Georgia, and one month before the invasion of Cape Gloucester. (See Chart 2.) Admiral Halsey had altered the plan by managing to start his invasion of New Georgia on 30 June. In June General MacArthur, in ordering the Markham Valley-Huon Peninsula attack, directed Admiral Halsey to be ready to take southern Bougainville on orders from GHQ. (GHQ SWPA 01 34, 13 Jun 43, in GHQ SWPA G-3 Jnl, 14 Jun 43. This section is based in part on Craven and Cate, The Pacific: Guadalcanal to Saipan, pp. 245-51; Halsey and Bryan , Admiral Halsey's Story, pp. 173-74; Morison, Breaking the Bismarcks Barrier, pp. 279-84; Maj. John N. Rentz, USMCR, Bougainville and the Northern Solomons (Washington, 1948), Ch. 1; The Bougainville Campaign, MS, prepared by Hist Sec G-2, SOPACBACOM, Vol. I, Ch. 1, OCMH. None of these, however, is entirely satisfactory for they do not employ Southwest Pacific Area sources.)

At this time Admiral Halsey, planning in accordance with ELKTON III, intended to use the 3d Marine Division and the 25th Division against southern Bougainville, the 2d Marine and 3d New Zealand Divisions against Rabaul. (Rad, Comdr Third Flt to CINCSWPA, 21 Jun 43, in GHQ SWPA G-3 Jnl, 23 Jun 43.)

Before long, however, the 25th Division, sent into New Georgia, was too worn for further combat and the 2d Marine Division was ordered to invade the Gilberts instead of Rabaul. (The 25th Division stayed on Guadalcanal after the conclusion of the campaign there. It had little opportunity for rest and reorganization before moving to New Georgia.)

Tactical planning for Bougainville began in the South Pacific in July when Halsey assigned the Commanding General, I Marine ng General, I Marine Amphibious Corps, to command the ground forces. (Map 15)

His mission was the seizure of Buin, Kahili, and Tonolei Harbor on southern Bougainville and of the nearby islands in Bougainville Strait- the Shortlands, Faisi, and Ballale, where there were then an estimated twenty thousand Japanese soldiers and sailors.

Near the end of July Admiral Halsey suggested a change in plan to General MacArthur. It was based on two assumptions: first, that the objectives of the operation were denying the use of airfields and anchorage to the Japanese and securing airfields and anchorages for the Allies, as a step toward the capture of Rabaul; and second, that because terrain, strategic position, and Japanese dispositions indicated that southern Bougainville was extremely important to the Japanese, the operation would be a major one.

With the difficulties of the then bogged- down New Georgia invasion and the success of the artillery on the offshore islands against Munda both obviously in mind, he suggested that he could save men, materiel, and time by avoiding the Bougainville mainland completely. He proposed to seize the Shortlands and Ballale, to emplace artillery on the former with the mission of interdicting Kahili, to build one or more airfields in the Shortlands, and to use the anchorages there that the Japanese 8th Fleet then employed regularly. MacArthur heartily approved the scheme. (Ltr, COMSOPAC to CINCSWPA, 26 Jul 43, sub: Bougainville Opn, in GHQ SWPA G-3 Jnl, 31 Jul 43; Rad, CINCSWPA to Comdr Third Flt, 4 Aug 43, in GHQ SWPA G-3 Jnl, 4 Aug 43; COMSOPAC War Diary, 26 Jul and 4 Aug 43 entries.)

Further Change in Plan

By early September, however, Admiral Halsey had decided on a further change in plan. Several factors influenced his decision. The impressive and inexpensive success on Vella Lavella had demonstrated once more the validity of the old principle of striking soft spots, when possible, in preference to headlong assault against fixed positions. Further, reconnaissance had indicated that airdrome sites on the Shortlands were not very good. Landing in the Shortlands, which the Japanese were believed to be reinforcing, would entail heavy losses; poor beaches would impede the landing of heavy construction equipment and artillery for the neutralization of Kahili.

It was also estimated that assaulting the Shortlands-Ballale-Faisi area would require two divisions, while two more would be needed to operate on southern Bougainville proper. As the South Pacific had but four divisions--the 37th and Americal Divisions of the U.S. Army, the 3d Marine Division, and the 3d New Zealand Division--that were considered fit to fight, no more advances would be possible for months. (The 2d Marine Division was due to leave; the 25th and 43d Divisions were due for rest and rehabilitation.)

Looking for a method of neutralizing the southern Bougainville-Shortlands area without capturing it, a method that would retain enough troops for a major forward move later, Halsey acted on the advice of his principal subordinate commanders. He decided in favor of increased air effort from the New Georgia fields against southern Bougainville and Buka. Starting about 1 November, he proposed to capture the Treasury Islands and Choiseul Bay as airfield, radar, and PT base sites from which to "contain and strangle" southern Bougainville and the Shortlands.

He proposed that after the mainland of Bougainville had been reconnoitered he and MacArthur could decide whether to advance from Choiseul to Kieta on the cast coast or from the Treasuries to Empress Augusta Bay on the west if Post-CARTWHEEL plans required the establishment of positions on the mainland of Bougainville. (Ltr, Halsey to CINCSWPA, 9 Sep 43, sub: ELKTON III-S Bougainville Objectives, in GHQ SWPA G-3 Jnl, 10 Sep 43; Memo, Adm Fitch, Gen Harmon, Maj Gen Charles D. Barrett [CG I Mar Amphib Corps], and Adm Wilkinson for COMSOPAC, 7 Sep 43, no sub, ABC 384 (1-17-43) Sec 2; Halsey, Narrative Account of the South Pacific Campaign, p. 8, OCMH; Harmon, The Army in the South Pacific, p. 9, OCMH. Some advocated bypassing Bougainville completely in favor of a jump to Emirau in the Saint Matthias group northwest of Kavieng.)

This plan was consistent with ELKTON III, and varied only slightly from the July schemes approved by MacArthur. But by now, MacArthur, perhaps aware of the decision to neutralize rather than capture Rabaul, and obviously anxious to hurry Up CARTWHEEL and get started on the drive toward the Philippines, had changed his mind about the scope and nature of the operation.

Thus when Halsey's chief of staff, Rear Adm. Robert B. Carney, and his new war plans officer, Col. William E. Riley, USMC, presented the Treasuries-Choiseul plan to MacArthur at GHQ on 10 September, MacArthur was against it. With the successful airborne move to Nabzab in mind, he expressed his agreement with the principle of the bypass, but maintained that Halsey's plan would make it impossible for South Pacific aircraft to hit at Rabaul effectively before 1 March 1944. He wanted Halsey's aircraft established within fighter range of Rabaul in time to assist with the neutralization of Rabaul that would cover the Southwest Pacific's invasion of Cape Gloucester.

This would be necessary, MacArthur held, because Southwest Pacific air forces could not attack all the objectives (including Madang and Wewak) that would have to be neutralized in order to protect the invasions of Cape Gloucester and of Saidor, on the north coast of the Huon Peninsula. Southwest Pacific headquarters hoped to start Operation III (chiefly Cape Gloucester) shortly after 1 December; Cape Gloucester itself would probably be invaded between 25 December 1943 and 1 January 1944. Therefore it would be necessary for South Pacific forces to establish themselves on the mainland of Bougainville about 1 November. So important was the operation that MacArthur tacitly approved commitment of the major part of South Pacific ground forces.

Specifically, he proposed the following outline plan:

    1. 15 October-1 November, Southwest Pacific air forces would make heavy attacks against Japanese aircraft, air installations, and shipping at Rabaul;

    2. 20-25 October, South Pacific forces would occupy the Treasuries and positions on northern Choiseul in order to establish radar positions and PT boat bases;

    3. 1 November, South Pacific forces would occupy Empress Augusta Bay on the west coast of Bougainville in order to establish airfields within fighter range of Rabaul;

    4. 1-6 November, the Southwest Pacific would continue air attacks on Rabaul and would assist in the neutralization of Buka;

    5. 25 December 1943-1 January 1944, Southwest Pacific forces would seize Cape Gloucester and Saidor in order to gain control of Vitiaz and Dampier Straits and to secure airdromes for the neutralization of Kavieng. During this period South Pacific forces would neutralize Rabaul. (Ltr, MacArthur to Halsey, 11 Sep 43, no sub, and Notes for Memo on Conf Between Reps of SWPA and SOPAC, GHQ SWPA, 10 Sep 43. Both in GHQ SWPA G-3 Jnl, 11 Sep 43.).

General MacArthur stressed the importance of a landing on the mainland at another meeting on 17 September attended by General Harmon and Colonel Riley. Asked if he preferred a landing on the east or the west coast of Bougainville, he put the decision entirely in Admiral Halsey's hands.

And so on 22 September, Halsey issued warning orders which canceled all his earlier plans and assigned the units to constitute the invasion force. Admiral Wilkinson would lead it. The landing forces, under Wilkinson, were still to be under the commanding general of the I Marine Amphibious Corps. Halsey instructed Wilkinson and his units to be ready to carry out one of two plans: either they were to seize and hold the Treasury Islands and the airfield sites in the Empress Augusta Bay region on the west coast of Bougainville; or they were to seize the Treasuries and Choiseul Bay, build airfields, PT boat bases, and landing craft staging points, and in late December seize the Japanese airfield at Tenekau on the east coast of Bougainville. (Ltr, COMSOPAC to CG 1 Mar Amphib Corps, CTF 31, and CTF 33, 22 Sep 43, sub: Warning Order, in GHQ SWPA G-3 Jnl, 24 Sep 43. During this period Admiral Halsey received communications from Admiral King's office which seemed to require him to seize southern Bougainville and then Kieta and Buka. This confused the issue until Admiral Nimitz assured Halsey that the messages from King were estimates and not directives, and that Halsey was to operate under the provisions of the 28 March 1943 directive.)

Submarine Patrols

Submarines took patrols to the east coast and to Empress Augusta Bay to gather data, and South Pacific intelligence officers interviewed missionaries, traders, planters, coastwatchers, and fliers who had been shot down over Bougainville. The east coast patrol, carried by the submarine Gato, delivered an unfavorable report.

3rd MARINEs LANDING ON CAPE TOROKINA

The west coast patrol, composed of marines, debarked from the submarine Guardfish about ten miles northwest of Cape Torokina in Empress Augusta Bay. The marines were unable to examine Cape Torokina because it was occupied by the Japanese, but they took samples of soil similar to that at Torokina. When tested, it showed that Cape Torokina was suitable for airfields.

Between the sea and the mountains at Cape Torokina, which lay within fighter range of Munda, was a coastal plain of about seven square miles. It was lightly defended; Halsey estimated that there were about one thousand Japanese in the area. So forbidding were the surrounding mountains that the area was almost isolated from the strong Japanese garrisons in southern Bougainville.

Halsey and his planners estimated that if Allied forces seized Torokina the Japanese would require three or four months to bring enough heavy equipment over the mountains to launch an effective counterattack. But there were disadvantages. The heavy surf in Empress Augusta Bay, which had no protected anchorages, would make landing operations difficult. No more than 65 miles separated the cape from all the Japanese air bases on Bougainville, and Rabaul was only 215 miles to the northwest.

Admiral Halsey calculated the chances and decided on Torokina. In his words: "The conception was bold and the probability of provoking a violent air-land-surface action was accepted and welcomed on the premise that the by-products of enemy destruction would, in themselves, greatly further the over-all Pacific plan. Enthusiasm for the plan was far from unanimous, even in the South Pacific, but, the decision having been made, all hands were told to 'Get going.' (Halsey, Narrative Account of the South Pacific Campaign, p. 8, OCMH.)

Halsey informed MacArthur of his decision on 1 October. Expressing his complete agreement, MacArthur promised maximum air support from the Southwest Pacific. The invasion would be launched on 1 November. (Rad, Halsey to MacArthur,1 Oct 43, and Rad, MacArthur to Halsey, 1 Oct 43, in GHQ SWPA G-3 Jnl, 1 Oct 43.)

More Invasion of Bougainville

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