Operation Cartwheel

Bougainville

Forces and Tactical Plans

by James Miller, jr.

The Allies

Bougainville, the largest of the Solomon Islands, is 125 miles long on its northwest-to-southeast axis, and 30 to 48 miles wide. (This section is based on Morison, Breaking the Bismarcks Barrier, pp. 279-89; Halsey and Bryan, Admiral Halsey's Story, pp. 173-76; SOPACBACOM, The Bougainville Campaign, Vol. I, Ch. I, OCMH; Japanese Operations in the Southwest Pacific Area (Vol. II of MacArthur hist), Ch. IX, p. 216, OCMH; Southeast Area Naval Operations, in, Japanese Monogr No. 50 (OCMH), 7-8; 8th Area Army Operations, Japanese Monogr No. 110 (OCMH) pp. 85-103; 17th Army Operations, II, Japanese Monogr NO. 40 (OCMH), 95- 99; COMSOPAC Opn Plan 16-43, 12 Oct 43, in GHQ SWPA G-3 Jnl, 17 Oct 43)

Its mountainous spine comprises two ranges, the Emperor and the Crown Prince. Two active volcanoes, 10,000-foot Mount Balbi and 8,000-foot Mount Bagana, send continual clouds of steam and smoke into the skies. Mount Bagana, a stark and symmet rical cone, overlooks Empress Augusta Bay and is the most outstanding feature of the region's dramatic beauty.

The mountain range ends toward the southern part of the island, and there, on the coastal plain near Buin, the Japanese had built the airfields of Kahili and Kara. On the western coast the mountains slope down through rugged foothills and flatten out into a narrow and swampy coastal plain that is cut by many small rivers. These silt-laden streams constantly build bars across their own mouths and thus frequently change their courses.

Good harbors in varying stages of development were to be found at Buka, Numa Numa, Tenekau, Tonolei, and in the islands off the south coast. Empress Augusta Bay, exposed as it was to the open sea, was a poor anchorage. The Japanese had airfields at Buka and Bonis on either side of Buka Passage, at Tenekau, Kieta, Kara, and Kahili on the mainland, and at Ballale near the Shortlands, and had seaplane anchorages and naval bases in the Shortlands.

As on all the other islands, there were no real motor roads, only native trails near the coasts plus a few that led through the mountains.

The native population consisted of over forty thousand nominally Christian Melanesians, who were slightly darker in color than their fellows in the southern Solomons. Before the war about a hundred white missionaries, planters, traders, and government officials had lived on the island. Some of the natives, it was known, were pro-Japanese and had aided the enemy in rooting out the coastwatchers earlier in the year.

Allied intelligence agencies estimated enemy strength at about 37,500 soldiers and 2o,ooo sailors, and correctly reported that the Army troops belonged to the 17th 4rmy, commanded by General Hyakutake, who had been responsible for the direction of the Guadalcanal Campaign. ("Harukichi," listed in Miller, Guadalcanal: The First Offensive as Hyakutake's given name, is a mistranslation.)

Over 25,000 of Hyakutake's men were thought to be in the Buin-Shortlands area, with an additional 5,000 on the east coast of Bougainville, 5,000 more at Buka and Bonis, and light forces at Empress Augusta Bay. Air reconnaissance enabled the Allies to keep a fairly accurate count of Japanese warships and planes in the New Guinea-Bismarcks-Solomons area.

Admiral Halsey, in preparing his attack, was not embarrassed by too many ships. Admiral Nimitz was getting ready to launch his great Central Pacific advance in November and had removed many of Halsey's ships, leaving him but eight transports and four cargo ships, or enough shipping to carry one reinforced division in the assault. Because South Pacific commanders expected the Japanese to oppose the invasion with vigorous air attacks, they decided not to use the slow LST's for the assault. The South Pacific had one carrier force, Task Force 38 under Rear Adm. Frederick C. Sherman, consisting of the 910-foot aircraft carrier Saratoga, the light carrier Princeton, two antiaircraft cruisers, and ten destroyers. Nimitz, in response to Halsey's requests for additional cruiserdestroyer and carrier task forces, assured Halsey that Central Pacific forces would be within reach to assist if necessary, and agreed to send Halsey another carrier task force on or about 7 November. (Ltr, Adm Duncan to Gen Smith, Chief of Mil Hist, 16 Nov 53, no sub, OCMH.)

Halsey issued the basic orders for the operation on 12 October. He organized five task forces similar to those that had made up the New Georgia attack forces. They were: Task Force 31 (the attack force), under Admiral Wilkinson; Task Force 33 (South Pacific land- based aircraft), under Admiral Fitch; Sherman's Task Force 38; the cruisers and destroyers of Admiral Merrill's Task Force 39; and Captain Fife's submarines in Task Force 72.

The submarines were to carry out offensive reconnaissance in the waters of the Bismarck Archipelago, and would be supplemented in their work by Central Pacific submarines operating out of Pearl Harbor. Merrill's ships would support the invasion by operating against enemy surface ships and by bombarding Buka and the Shortlands. Halsey also planned to employ Sherman's Task Force 38 in a raid against Buka and Bonis, which lay beyond effective fighter range of the New Georgia airfields. Task Force 33 was ordered to carry out its usual missions of reconnaissance, destruction of enemy ships and aircraft, and air cover and support of the invasion force. Air Command, Solomons, which was part of Task Force 33, was making its intensive effort during October against the Japanese airfields in southern Bougainville and the outlying islands, so that these areas could safely be bypassed. Arrangements for local air support were the same as for New Georgia. The local air commander with the invasion force was designated, as a subordinate of Twining's, Commander, Aircraft, Northern Solomons, and would take command of all support aircraft as they took off from their bases.

Admiral Wilkinson's invasion force, Task Force 31, consisted of eight transports, four cargo ships, two destroyer squadrons, mine craft, almost all the South Pacific's PT squadrons, and a large force of ground troops under the Commanding General, I Marine Amphibious Corps (IMAC).

LT. GEN. ALEXANDER A. VANDEGRIFT

The ground commander was General Vandegrift, USMC, an apple-cheeked, deceptively soft-spoken Virginia gentleman, who had won distinction by his conduct of operations on Guadalcanal from 7 August 1942 until December of that year. Vandegrift was at this time slated to become commandant of the Marine Corps in Washington, but was given the Bougainville command temporarily because Maj. Gen. Charles D. Barrett, who had replaced Vogel in command of the I Marine Amphibious Corps, had met accidental death in Noum6a. Halsey's choice for the corps command fell upon Maj. Gen. Roy S. Geiger, USMC, another hero of Guadalcanal, who was then in Washington as Director of Marine Corps Aviation. Vandegrift was to exercise the command until Geiger could arrive.

Ground forces assigned to the attack included the following: I Marine Amphibious Corps headquarters and corps troops; 3d Marine Division; 37th Division; 8th Brigade Group, 3d New Zealand Division; 3d Marine Defense Battalion; 198th Coast Artillery Regiment (Antiaircraft); 2d Provisional Marine Raider Battalion; ist Marine Parachute Battalion; naval construction and communications units, and a boat pool.

In area reserve, to be committed on orders from Admiral Halsey, were the Americal Division in the Fijis; the 2d Battalion, 54th Coast Artillery (Harbor Defense) Regiment at Espiritu Santo; and the 251st Coast Artillery (Antiaircraft) Regiment in the Fijis.

Naming D Day as 1 November, the date for the invasion of Empress Augusta Bay, Halsey ordered Task Force 31 to seize and hold the Treasury Islands on D minus 5 (27 October) and establish radar positions and a small naval base. Wilkinson's main attack would be the seizure of Empress Augusta Bay on 1 November, which would be followed by the speedy construction of two airfields on sites to be determined by ground reconnaissance after the troops had landed. Task Force 31 was initially ordered to be ready to establish a PT base on northern Choiseul. This part of the plan was changed on the recommendation of Vandegrift, who argued that the Treasury landings might reveal to the Japanese the intention to invade Empress Augusta Bay. Halsey, Wilkinson, and Vandegrift decided instead to use the 2d Marine Parachute Battalion in a twelve-day raid on Choiseul which they hoped would mislead the enemy into believing that the real objective lay on Bougainville's east coast. (General Geiger described the plan of maneuver as "a series of short right jabs designed to throw the enemy off balance and conceal the real power of the left hook to his midriff at Empress Augusta Bay." He must have boxed left-handed.)

Halsey made Wilkinson, whose headquarters was then at Guadalcanal, responsible for co-ordination of all amphibious plans. Wilkinson was to command all elements of Task Force 31 until, at a time agreed upon by him and the ground commander, direction of all air, ground, and naval forces at Empress Augusta Bay would be transferred to the latter.

Wilkinson divided Task Force .31 into a northern force, which he commanded himself, for the main attack and a southern force, led by Admiral Fort, for the Choiseul raid and the seizure of the Treasuries. The assault echelon of the northern force, scheduled to land at Empress Augusta Bay on D Day, included destroyers, the transports and cargo ships, and Maj. Gen. Allen H. Turnage's 3d Marine Division, less one regimental combat team and plus supporting units. The Treasuries echelon of the southern force was made up of 8 APDs, 2 LSTs, 8 LCIs, 4 LCTs, 2 APCs, the 8th Brigade Group of the 3d New Zealand Division, the 198th Coast Artillery, A Company of the 87th Naval Construction Battalion, and communications and naval base detachments. The parachute battalion would be transported by four APD's escorted by destroyers. The 37th Division, in corps reserve, would be picked up at Guadalcanal by the northern force transports and would start arriving at Bougainville soon after D Day to help hold the beachhead.

Guadalcanal and the Russells were to serve as the main staging and supply bases. However, the shortage of shipping led the I Marine Amphibious Corps to shorten the lines by establishing a supply base at Vella Lavella.

Plans called for the Vella depot to be stocked with a thirty-day supply of rations and petroleum products, but so strained was South Pacific shipping that only a ten-day supply had been stocked at Vella Lavella by 1 November.

During the last half of October the ground units completed their training and conducted final rehearsals. The 3d Marine Division, part of which had served in Samoa in 1942 before joining the main body in New Zealand, had recently transferred from New Zealand to Guadalcanal. It completed its amphibious and jungle training there and rehearsed for Empress Augusta Bay in the New Hebrides from 16 to 20 October.

The 37th Division, returned from New Georgia to Guadalcanal in September, likewise conducted amphibious and jungle training at Guadalcanal. The 3d Marine Defense Battalion, which after serving in the Guadalcanal Campaign had been sent to New Zealand and from there back to Guadalcanal, rehearsed there. The 8th Brigade practiced landings at Efate en route to Guadalcanal from New Caledonia, and from 14 to 17 October rehearsed at Florida.

The Japanese

The Japanese fully expected Halsey to attack Bougainville and were busy preparing to meet the invasion. Imperial Headquarters' orders in September had stressed the importance of Bougainville as an outpost for Rabaul, and General Imamura had instructed General Hyakutake to make ready. This the 17th Army commander did, acting in conjunction with the commander of the 8th Fleet. The Japanese planned to use air and surface strength to smash any Allied attempt' at invasion before the assault troops could get off their transports. But if troops did succeed in getting ashore, the Japanese hoped to attack and destroy their beachheads.

Hyakutake's army consisted mainly of the 6th Division, Lt. Gen. Masatane -Kanda commanding. (This division had acquired an unsavory reputation for indiscipline by its sack of Nanking, China, in 1937). Also assigned were the 4th South Seas Garrison Unit (three infantry battalions and one field artillery battery), and field artillery, antiaircraft artillcry, and service units. Imamura was sending four rifle battalions and one artillery battalion of the 17th Division from New Britain to northern Bougainville; these were due in November. (The units attached to the Southeastern Detachment had been returned to their parent organizations. The Detachment was inactivated in December.)

Hyakutake, whose headquarters was on tiny Erventa Island near Tonolei Harbor, had disposed most of his strength to cover the Shortlands, Buin, and Tonolei Harbor, the rest to protect Kieta and Buka.

Some 26,800 men -- 20,000 of the 17th Army and 6,800 of 8th Fleet headquarters and naval base forces -- and an impressive number of guns ranging from machine guns to 140-mm. naval rifles were stationed in southern Bougainville and the islands. Over 4,000 men were at Kieta, and the arrival of the 17th Division units would bring the Buka Passage garrison to 6,000. (These figures are taken from Southeast Area Naval Operations. III, Japanese Monogr No. 50 (OCMH), 7-8. Army accounts do not give strength figures.)

The unpromising nature of the terrain on the west coast of Bougainville had convinced Hyakutake that the Allies would not attempt to land there. Consequently only a small detachment was stationed at Empress Augusta Bay. Hyakutake was aware that he would be outnumbered and outgunned in any battle, but like most of his fellow Japanese generals he placed great faith in the superior morale he believed his troops possessed.

"The battle plan is to resist the enemy's material strength with perseverance, while at the same time displaying our spiritual strength and conducting raids and furious attacks against the enemy flanks and rear. On this basis we will secure the key to victory within the dead spaces produced in enemy strength, and, losing no opportunities, we will exploit successes and annihilate the enemy." (17th Army Operations, II, Japanese Monogr No. 40 (OCMH), 95)

Pride goeth before destruction, and an haughty spirit before a fall.

More Invasion of Bougainville

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