Key Allied victories in the Pacific have been singled out as seminal turning points against the Japanese. The American Navy’s sinking of four enemy carriers at Midway crippled future Imperial Japanese Navy (IJN) initiatives on the scale mounted during the war’s initial six months.
The six-month-long, grueling Japanese defense and ultimate conquest of Guadalcanal by American land, sea, and air forces—after the initial Marine amphibious invasion of that southern Solomon island on August 7, 1942—halted the Japanese southeastward strategic advance to sever the sea lanes to the Antipodes.
What has been ignored, however, is the backbreaking series of defeats that the Japanese suffered in their attempts to defend New Georgia, Kolombangara, and Bougainville in the Central and Northern Solomons. The losses of Imperial Japanese Army (IJA) units, IJN ships, and aircraft and crews could never be replaced after the defeats suffered on these hellacious jungle islands, especially given the requisite presence of Imperial forces on the Central Pacific and New Guinea fronts.
Major General Allen H. Turnage, commanding the 3rd Marine Division, which had invaded Bougainville in November 1943, wrote, “Never had men in the Marine Corps had to fight and maintain themselves over such difficult terrain as was encountered on Bougainville.”
Major General Alexander A. Vandegrift, who commanded the 1st Marine Division on Guadalcanal and then the I Marine Amphibious Corps (IMAC) for the Bougainville landings, commented that the Bougainville “jungle [was] worse than we had found on Guadalcanal.”
Stanley Frankel, the U.S. Army’s 37th Infantry Division historian, wrote about the Japanese counteroffensive against the U.S. Army’s XIV Corps perimeter at Cape Torokina on Bougainville in March 1944: “The curtain was about to rise on one of the bloodiest, most fanatical Banzai attacks made by the Japanese in the South Pacific War … against a civilian army of battling clerks, farmers, mechanics, schoolboys, business men.”
Another Marine veteran of Guam and Iwo Jima recounted, “Of all the 28 months I spent overseas, nothing compared to Bougainville for miserable living conditions…. Bougainville had to be the closest thing to a living hell that I ever saw in my life.”
The Pacific campaigns before and after Bougainville—Guadalcanal, Tarawa, the Marshall Islands, Saipan, Guam, Peleliu, Iwo Jima, and Okinawa—seemed to be much more “headline-grabbing” amphibious operations than the largely forgotten six-month long Marine and Army efforts at Cape Torokina on Empress Augusta Bay.
Possible explanations for Bougainville being overshadowed stem from a paradigm shift in Allied strategy in the South Pacific. After the war, a Japanese intelligence officer admitted that, after the bloody frontal assaults along Papua’s northern coast at Buna during late 1942 into early 1943, the Americans had begun to display a new strategic initiative to invade Japanese-held areas where they were the least defended.
The officer said, “This was the type of strategy we hated most. The Americans, with minimum losses, attacked and seized a relatively weak area, constructed airfields, and then proceeded to cut the supply lines to troops in that area. Without engaging in a large-scale operation, our strongpoints were gradually starved out. [The] Americans flowed into our weaker points and submerged us, just as water seeks the weakest entry to sink a ship.”
Historian Stephen Taafe summed up this emerging strategy as “cutting off and isolating their strong points and, in effect, transforming them into vast jungle prison camps.”
In May 1942, before the fighting for Papua commenced, General Douglas MacArthur, the commander-in-chief of the Southwest Pacific Area (SWPA), had rashly boasted that, given three infantry divisions and two aircraft carriers, he could capture the Japanese bastion of Rabaul on the northeastern tip of the island of New Britain in the Bismarck Archipelago. The Joint Chiefs of Staff (JCS) prudently shelved this bombastic notion. In early June 1943, the JCS completed a survey, which concluded just the opposite. A direct invasion of New Britain would be too costly. Rabaul should be neutralized instead.
The next month, General George C. Marshall, the U.S. Army Chief of Staff, communicated to MacArthur that with the SWPA commander capturing Wewak on the northeast New Guinea coast and Manus in the Admiralty Islands group along with Admiral WIlliam F. “Bull” Halsey’s South Pacific Force’s eventual seizure of Kavieng on New Ireland to the north of Rabaul he believed that Rabaul could be encircled and effectively neutralized using U.S. air power.
When MacArthur persisted with his urging that Rabaul be directly invaded, Allied planners at the Quebec Conference of the Combined Chiefs of Staff in August 1943 were adamant and formalized the strategy codenamed Operation Cartwheel to neutralize Rabaul.
Rabaul was the headquarters and main supply base for both the Japanese Southeastern Army and the Southeastern Fleet and lay directly northwest of Bougainville. Air units based at Rabaul were the responsibility of the Eleventh Air Fleet. Despite extensive losses, the IJN continued to reinforce its air units with approximately 50 planes a month flown in from Truk in the Caroline Islands.
In all of New Britain, the IJA could muster more than 97,000 men. To defend the region around Rabaul in November 1943, the IJA had more than 76,000 men. There were four natural harbors there, with Simpson Harbor and its excellent docking facilities capable of handling 300,000 tons of shipping.
As Admiral Samuel Morison commented, “Tarawa, Iwo Jima, and Okinawa would have faded to pale pink in comparison with the blood that would have flowed if the Allies had attempted an assault on Fortress Rabaul.”
The Solomon Island chain is more than 500 miles long. Bougainville is one of the most northern islands in the chain, as well as the largest, 130 miles long and 30 miles wide. Bougainville’s strategic importance lay with its location just over 200 air miles from Rabaul.
Topographically, Bougainville possessed two central mountain ranges, the Emperor Range in the north and the lower, less rugged one to the south, the Crown Prince Range, with the former having two active volcanoes—Mount Balbi at over 10,000 feet and Mount Bagana. Except for some roads in the south that could accommodate wheeled transport, overland movement was limited to primitive trails through the dense jungle interior.
Most important of the island routes were the Numa Numa Trail, which extended southwest from Numa Numa on the northeast coast to Empress Augusta Bay, and the East-West Trail running northwest from Buin on the southern tip to Gazelle Harbor below Empress Augusta Bay.
The invasion of Bougainville, along with construction of airfields there, would be a major part of Operation Cartwheel. Bougainville was to be assaulted in the final phase of the bloody campaign up the Solomon Island chain. However, due to Bougainville’s proximity to Rabaul, it was heavily garrisoned by the Japanese.
Bougainville was headquarters for the Japanese Northern Solomons Defense Force with its main base at Buin located on the southeastern tip of the island, across from which were the Shortland Islands, Faisi, and Ballale. The IJA 17th Army Headquarters and the IJA 6th Division, the latter having achieved notoriety for atrocities committed in China, had 15,000 men around Buin airfield on the island’s southern tip.
There were other airfields in the south, including Kahili, Kieta, and Kara. The IJN’s Eighth Fleet had several hundred more men on Bougainville, and there were more than 10,000 Japanese troops and naval coast artillery in the Shortland Islands and nearby Ballale Island, with its airfield being an IJN operation. In the extreme northwest of the island abutting Buka passage was an airfield at Bonis.
Additionally, at the Buka airbase just to the north of Bougainville the IJA had garrisoned 5,000 men while the IJN stationed 1,000 sailors at a seaplane base. At Empress Augusta Bay on the island’s western side the IJA had stationed only a small infantry garrison.
After 15 months of Japanese occupation, Bougainville’s native Melanesian population was thoroughly pro-Japanese. The Allies were unable to ascertain current intelligence about Japanese movements because many of the coast watchers had been captured, and those still at large were unable to move around the island safely. By July 1943, all of the remaining Allied coastwatchers were evacuated from Bougainville.
The Japanese knew that a battle for Bougainville was going to be more crucial than the previous losing struggle for Guadalcanal. Also, the Japanese still retained a distinct advantage in the Solomons. Even though they had lost Guadalcanal their fighter aircraft had longer range than American planes.
Additionally, Combined Fleet Admiral Isoruku Yamamoto had been continually building up his airfields in the Northern Solomons as staging areas, as well as at Vila on Kolombangara and at Munda on New Georgia. Japanese planes could be dispatched from Rabaul to New Georgia, where they could refuel and then go on to attack the American bases at Tulagi and Guadalcanal and return the same way with emergency airfields available for damaged planes to conserve the diminishing number of skilled pilots, many of whom had been lost in air combat over Guadalcanal.
The American planes, especially the fighters, did not have the range to reach Rabaul and return to U.S. bases. Recognizing this logistical advantage, Yamamoto intended to reinvigorate his air attacks on Guadalcanal from bases on Rabaul after the Japanese evacuation from Guadalcanal in early February 1943.