|Bougainville Campaign (1943–45)|
|Part of the Pacific Theatre of World War II|
United States Army soldiers hunt Japanese infiltrators on Bougainville in March 1944.
| United States
Colony of Fiji
|Empire of Japan|
|Commanders and leaders|
| William F. Halsey
R. A. Row
Theodore S. Wilkinson
Alexander A. Vandegrift
Allen H. Turnage
Robert S. Beightler
Roy S. Geiger
Oscar W. Griswold
H. E. Barrowclough
| Hitoshi Imamura
Kiyoto Kagawa †
|144,000 American troops
30,000 Australian troops
|Casualties and losses|
|18,500–21,500 dead[Note 1]|
The Bougainville Campaign (Operation Cherry Blossom) was a series of land and naval battles of the Pacific campaign of World War II between Allied forces and the Empire of Japan. It was part of Operation Cartwheel, the Allied grand strategy in the South Pacific. The campaign took place in the Northern Solomons in two phases: the first phase, in which American troops invaded and held the Perimeter around the beachhead, lasted from November 1943 through November 1944; the second phase, in which British Commonwealth troops mopped up pockets of starving, isolated Japanese, lasted from November 1944 until August 1945, when the last Japanese on the island surrendered.
- 1 Japanese occupation
- 2 Allied planning
- 3 Landings at Cape Torokina
- 4 November 1943: Expanding the beachhead
- 5 December 1943: Securing the Perimeter
- 6 January–February 1944: Encircling Rabaul
- 7 March 1944: Japanese counterattack
- 8 Second phase: November 1944 – August 1945
- 9 Namesake
- 10 Notes
- 11 References
- 12 Further reading
Before the war, Bougainville had been administered as part of the Australian Territory of New Guinea, even though, geographically, Bougainville is part of the Solomon Islands chain. The United Kingdom and Germany had traded it for another islands territory which became British rather than German. As a result, the campaign is referred to as part of both the New Guinea and the Solomon Islands campaigns.
During their occupation the Japanese constructed naval aircraft bases in the north, east, and south of the island; but none in the west. They developed a naval anchorage at Tonolei Harbor near Buin, their largest base, on the southern coastal plain of Bougainville. On the nearby Treasury and Shortland Islands they built airfields, naval bases and anchorages. These bases helped protect Rabaul, the major Japanese garrison and naval base in Papua New Guinea, while allowing continued expansion to the south-east, down the Solomon Islands chain, to Guadalcanal.
In March–April 1942, the Japanese landed on Bougainville as part of their advance into the South Pacific. At the time, there was only a small Australian garrison on the island which consisted of about 20 soldiers from the 1st Independent Company and some coastwatchers. Shortly after the Japanese arrived, the bulk of the Australian force was evacuated by the Allies, although some of the coastwatchers remained behind to provide intelligence. Once secured, the Japanese began constructing a number of airfields across the island. The main airfields were on Buka Island, the Bonis Peninsula in the north, at Kahili and Kara, in the south, and Kieta on the east coast, while a naval anchorage was constructed at Tonolei Harbor near Buin on the southern coastal plain, along with anchorages on the Shortland Islands group.
The airfield at Kahili was known by the Japanese as Buin Airfield, and to its south was an airfield on Ballale Island in the Shortland Islands. These bases allowed the Japanese to conduct operations in the southern Solomon Islands and to attack the Allied lines of communication between the United States, Australia and the Southwest Pacific Area.
At the opening of the Allied offensives, estimates of Japanese strength on Bougainville varied widely, ranging between 45,000 to 65,000 Army, Navy, and labour personnel.[Note 2] These forces constituted the Japanese 17th Army, commanded by General Harukichi Hyakutake.
Hyukatake reported to General Hitoshi Imamura, commander of the Japanese Eighth Area Army, headquartered at Rabaul on New Britain Island. Naval command at Rabaul was the responsibility of Vice Admiral Jinichi Kusaka, commander Southeast Area Fleet. The level of cooperation between these two officers was greater than that usually found between the branches of the Japanese armed forces.
Choice of Bougainville
Reduction of the main Japanese base at Rabaul was the ultimate goal of the Allied offensive in the Solomons (Operation Cartwheel). That city was already within range of Allied heavy bombers, but a closer airfield was needed for light bombers and escort fighters. Thus, the entire island of Bougainville did not need to be occupied; only enough relatively flat land to support an airbase was required. This "was the one and only reason why the JCS authorized Halsey to seize a section of Bougainville: to establish forward airfields for strikes on Rabaul."
The area around Cape Torokina was settled on since, among other things, the Japanese were not there in force and had no airfield there. Also, Empress Augusta Bay had a somewhat protected anchorage, and the physical barriers in back of the cape (mountain ranges, jungle) meant that mounting a counterattack would be beyond the capabilities of the Japanese for weeks, possibly months.
Preparations for the landings
Bougainville lay within the Southwest Pacific Area, so operations were nominally under the command of General Douglas MacArthur, whose headquarters were in Brisbane, Australia. Although MacArthur had to approve all major moves, he willingly gave planning and operational control to Admiral William F. Halsey, Commander U.S. Third Fleet, headquartered at Nouméa on New Caledonia. In mid-October, Halsey set 1 November as the date for the invasion of Bougainville.
By early October, it was clear to the Japanese that a follow-up offensive to the Allied capture of the New Georgias was in the works, even though the target was uncertain. Commander of the Japanese Combined Fleet Admiral Mineichi Koga, flying his flag aboard battleship Musashi at Truk Lagoon, ordered all of his carrier aircraft to Rabaul. These planes would combine with the land-based air force already there and pound Allied bases and supply routes, a plan the Japanese called Operation RO. In the event, this plan achieved very little besides further attrition to the Japanese air arm.
To confuse the Japanese as to the Allies' real target, two other invasions were carried out. The Treasury Islands, a little to the southwest of the Shortlands, were occupied 27 October by the 8th Brigade Group, 3rd New Zealand Division under the command of Brigadier R.A. Row and a temporary landing was effected on Choiseul, one of the major islands in the Solomons chain.
Unlike on Guadalcanal and the New Georgias, the Allies could get no help in planning the invasion of Bougainville from British Commonwealth coastwatchers or Australian Army detachments. The Japanese had driven them off the island long before plans for Operation Cherry Blossom began.
Rear Admiral Theodore Stark "Ping" Wilkinson, Commander Third Fleet Amphibious Forces, was assigned by Halsey to direct the landings at Cape Torokina from aboard his flagship, the attack transport George Clymer.
The ships under Wilkinson's command would disembark the I Marine Amphibious Corps under the command of Major General Alexander A. Vandegrift, USMC, victor of the land campaign on Guadalcanal. Vandegrift's force, a total of 14,321 men, consisted of the following:
Landings at Cape Torokina
First day: 1–2 November 1943
Three groups of transports converged in Empress Augusta Bay on the morning of 1 November. Unfortunately, the existing maps of the Bougainville coast were highly unreliable German Admiralty charts from about 1890. A few corrections had been made by reconnaissance flights and submarine scouting, but some longitudes were still wrong. "Near the end of the approach, when the navigating officer of a transport was asked by the captain for his ship's position, he replied, 'About three miles inland, sir!'"
To the forces, as they approached, Empress Augusta Bay presented a magnificent but somewhat terrifying spectacle. Behind the curved sweep of the shore line, a heavy, dark green jungle...swept up over foothills and crumpled ridges to the cordillera which was crowned by a smoking volcano, Mount Baranga, 8,650 feet above sea level...It was wilder and more majestic scenery than anyone had yet witnessed in the South Pacific...
From the difficult landings at Guadalcanal and the New Georgias, Admiral Wilkinson learned a significant lesson about the necessity of rapid unloading and getting his slow, vulnerable transports away from the landing area. To this end, he only loaded his transports half full and his cargo ships one-quarter full, and made sure that 30% of the troops on the beach assisted in unloading.
The Japanese, having never conceived that the Allies were capable of a move as bold as one to Empress Augusta Bay, were unable to mount an air assault on the invasion fleet. Admiral Wilkinson, grateful that his transports were able to land almost the entire troop contingent and a large amount of materiel unmolested by air attack, ordered them out of the area around sundown.
When word of the landings reached Rabaul, Vice Admiral Tomoshige Samejima, Commander Japanese Eighth Fleet, immediately embarked a thousand troops onto five destroyer-transports at Rabaul and sent them to Cape Torokina to effect a counterlanding. Escorting the transports was a force of two heavy cruisers, two light cruisers and six destroyers led by Vice Admiral Sentaro Omori. During the night voyage to Torokina, the Japanese ships were spotted by an American submarine and possibly by a search plane. Concerned that he had lost the element of surprise, Omori radioed Samejima to ask permission to send the slow-moving transports back to Rabaul, but to continue with the combat ships to attack the American transports that he assumed were still in Empress Augusta Bay. Samejima concurred, and Omori pressed ahead with his cruisers and destroyers.
At the same time, Rear Admiral A. Stanton "Tip" Merrill was steaming toward the Bay with four light cruisers and eight destroyers. The two forces met in the early morning hours of 2 November in the Battle of Empress Augusta Bay, in which the Japanese lost light cruiser Sendai and destroyer Hatsukaze.
Carrier raid on Rabaul
Admiral Koga, while unwilling to risk his precious aircraft carriers, did dispatch seven heavy cruisers to Rabaul, arriving 3 November. News of the cruisers' arrival in the area of operations greatly concerned Admiral Halsey: the Bougainville beachhead was still quite vulnerable and he had no heavy cruisers at all to oppose a bombardment. Taking a huge gamble, he ordered the only carrier force under his immediate command, Task Force 38 under Rear Admiral Frederick C. Sherman, to cripple or sink as much of the combat shipping in Simpson Harbor as possible. The resulting air strike, launched from Sherman's fleet carrier Saratoga and light carrier Princeton on 5 November, sank no ships but inflicted enough damage to convince Koga to withdraw the heavy cruisers. The beachhead at Cape Torokina was never shelled by a Japanese heavy cruiser.
This raid demonstrated the crucial importance of air dominance. Not only did air power alone remove the threat to Bougainville from large surface ships, but the raid was carried out using the carriers' full complement of fighters; combat air patrol for Sherman's task force was provided by the land-based Air Solomons command throughout the mission.
November 1943: Expanding the beachhead
Defense and expansion of the position at Cape Torokina involved protracted and often bitter jungle warfare, with many casualties resulting from malaria and other tropical diseases. Except for patrol skirmishes, all of the major combat to expand the beachhead occurred in the Marine sector.
From 6–19 November, the remaining regiment of the 3rd Marine Division and the 37th Infantry Division (Army) were landed and the beachhead gradually expanded. On their third attempt, the Japanese successfully landed four destroyer-loads of men just beyond the eastern limit of the American beachhead before dawn on 7 November (to the great embarrassment of the PT boat base on Puruata Island, the Japanese effected this landing completely undetected by the Americans). The Marines annihilated this force the next day in the Battle of Koromokina Lagoon.
While escorting one of the invasion echelons to the Torokina beachhead on 9 November, some of Admiral Merrill's sailors witnessed an extraordinary incident that highlighted some of the extreme cultural differences at play in the Pacific Theatre:
On their way north, the bluejackets topside in destroyer Spence were goggle-eyed at an exhibition of Japanese bushido. Ordered to investigate a life raft, they observed what appeared to be seven bodies in it. The seven bodies suddenly sat up and started talking. One of them, apparently the officer, broke out a 7.7-mm machine gun, which each man in succession placed in his mouth, while the officer fired a round which shot the back of the man's head off. After six had been bumped off, the officer stood up, addressed a short speech in Japanese to Spence's commanding officer on the bridge, and then shot himself.
Parts of two Marine raider battalions drove away Japanese who were blocking the Piva branch of the Numa Numa Trail in the 8–9 November Battle for Piva Trail. The Marines then selected sites in the area for two airstrips (the fighter strip at the beach was already being built). Also on 9 November, Major General Roy S. Geiger, USMC, took over command of the I Marine Amphibious Corps from General Vandegrift. Four days later, he assumed command of the entire Torokina beachhead area from Admiral Wilkinson. By this time, the Perimeter, as it was called, covered about 7,000 yards of beach front and had a circumference of about 16,000 yards.
The trails to new airstrip sites had to be cleared, and General Turnage assigned this task to the 21st Marine Regiment. A Japanese ambush in the area resulted in the 13–14 November Battle of the Coconut Grove, ending with the Marines in control of the point where the Numa Numa and East West Trails crossed. Among those killed was Lieutenant Stanley P. Wright, whose poem "A Marine to His Girl" appeared in Eleanor Roosevelt's column My Day in January 1944.
At Rabaul, General Imamura was still convinced that the Allies did not mean to stay long at Torokina—he was sure it was just a stepping stone. He thus had no interest in mounting a decisive counterattack on the Allied beachhead using the substantial number of troops he already had in the southern part of Bougainville. Instead, he reinforced the Buka Island area, just off the north coast of the larger island, believing it to be the Allies' real target. In other words, the Army insisted on repeating the error of Guadalcanal; the Navy could not convince Imamura of the Americans' real intentions.
The 18–25 November Battle of Piva Forks effectively wiped out an entire Japanese infantry regiment. Even so, the beachhead was still not an entirely safe place. The day after the end of the Piva Forks action, as the sixth echelon of the invasion force was unloading at the beachhead, Japanese artillery fired on the landing ships, inflicting casualties. The Marines silenced these guns the following day.
On Thanksgiving Day, as the Battle of Piva Forks was ending, the Battle of Cape St. George took place in the waters between Buka and New Ireland. Three destroyer transports full of troops, escorted by two destroyers, all under the command of Captain Kiyoto Kagawa, were on their way to reinforce Buka. Admiral Halsey directed five destroyers under Captain Arleigh A. "31-Knot" Burke to intercept. The encounter ended with the sinking of Onami, Makinami and Yugumo, as well as the death of Captain Kigawa. No hits were scored on Burke's vessels.
On 28–29 November, the ill-fated Koiari Raid was carried out. A Marine detachment that was supposed to block a Japanese flank attack faced being overrun and had to be rescued.
December 1943: Securing the Perimeter
Under extremely difficult conditions, the Naval Construction Battalions (CBs or Seabees) and a group of New Zealand engineers carried on work on the three airstrips. The fighter strip at the beach was the first to begin full-time operations (10 December). The Japanese Army command at Rabaul was certain that the Allies would be moving on from Torokina; Imamura ordered a build-up of the defenses at Buin, on the southern tip of Bougainville.
In November and December the Japanese emplaced field artillery on the high ground around the beachhead, concentrated in a group of hills along the Torokina River overlooking the eastern perimeter. They shelled the beachhead, targeting the airstrips and the supply dumps. The 3rd Marine Division extended its lines to include the hills in a series of operations that lasted from 9–27 December. One hill, "Hellzapoppin Ridge", was a natural fortress 300 feet (91 m) long, with sharp slopes and a narrow crest that overlooked much of the beachhead. The Japanese constructed extensive positions on the reverse slopes using natural and artificial camouflage. The 21st Marines attacked Hellzapoppin Ridge but were driven off on 12 December. Several air strikes missed the narrow ridge completely. Finally, co-ordinated air, artillery, and infantry attacks resulted in the capture of Hellzapoppin Ridge on 18 December. In the days that followed, the 21st Marines were also involved in fighting around Hill 600A, which was captured by 24 December 1943.
On 15 December, the I Marine Amphibious Corps and General Geiger were replaced by the Army's XIV Corps, led by Major General Oscar W. Griswold, the victor of the land campaign on New Georgia. On 28 December, the 3rd Marine Division, exhausted because most of the fighting had taken place in its sector, was replaced by the Army's Americal Division under Major General John R. Hodge. The 37th Division (Army), left behind at Torokina when the Marines pulled out, was then placed under Griswold's XIV Corps.
January–February 1944: Encircling Rabaul
The aerial reduction of Rabaul
Rabaul had already been raided multiple times from 12 October through 2 November by the heavy bombers of General George C. Kenney's Allied Air Forces Southwest Pacific Area. Significant damage was done to ground installations and the Japanese adapted by moving aircraft facilities underground.
Completion of the airstrips on Bougainville would allow the Allies to use smaller planes against Rabaul. Only such low-flying techniques as dive bombing and glide bombing could permit the pinpointing of anti-aircraft installations and vessels in the harbor. The fighter strip on the beach at Torokina began operations on 10 December, the inland bomber strip "Piva Uncle" followed on Christmas Day, and the inland fighter strip "Piva Yoke" on 22 January.
General Ralph J. Mitchell, USMC, took over the command of all land-based planes in the theater, called Air Command, Solomons (Airsols), on 20 November. Once the three airstrips in the Torokina Perimeter were fully functional, Mitchell moved Airsols headquarters there from Munda on New Georgia Island.
The first raids by Airsols aircraft had limited success. Japanese anti-aircraft fire, especially from ships, had improved greatly since Kenney's raids, and inflicted significant damage on the raiders. Gradually, however, the Americans developed new formations and tactics that brought about increasing attrition among the Japanese fighter arm. The Navy could no longer risk exposing its ships to the relentless air attacks, and by late January, Admiral Kusaka had banned all shipping except barges from Simpson Harbor (this, of course, removed any remaining naval threat to the Torokina beachhead)
By mid-February, when the Allies captured the Green Islands (see below), the base was incapable of sending air power to interfere. As of 8 March, while the Battle for the Perimeter was beginning on Bougainville (see below), Air Solomons stopped bothering with fighter escorts for its bombing missions to Rabaul
It is significant that the splendid harbor which in October 1943 had held some 300,000 tons of enemy shipping, and had sheltered powerful task forces of the Japanese Navy, was reduced to a third-rate barge depot.
Capture of the Green Islands
The Joint Chiefs of Staff had determined that Rabaul was to be encircled, with invasions of the Admiralty Islands and Kavieng on the north tip of the island of New Ireland, to begin 1 April at the earliest. Admiral Halsey, anxious to maintain offensive momentum, was unwilling to leave his forces idle until then. To that end, and to provide yet another airfield close to Rabaul, Halsey ordered his amphibious forces to invade the Green Islands, a group of small coral atolls about 115 miles east of Rabaul. Reconnaissance missions determined that the native Melanesians there were so well-disposed toward the Europeans, and had been so alienated by the Japanese, that no preliminary bombing or shelling would be performed.
On February 15, Admiral Wilkinson landed a contingent of New Zealanders under Major General Harold E. Barrowclough, who, like Griswold, was a veteran of New Georgia. With experience learned in previous invasions and extremely detailed staff work, the landings went off with great efficiency. In addition, interference from Japanese planes was minimal: "That so numerous a fleet could set thousands of troops ashore with impunity only 115 miles from Rabaul proved what good work AirSols had already accomplished."
The Greens provided a site for a PT boat base, and during the night of 1 March, PT-319 actually entered Simpson Harbor, and went undetected by the Japanese. This would have been inconceivable just two months earlier. In addition, a detachment of Seabees constructed an airfield, putting the Japanese base at Kavieng in range of AirSols planes for the first time.
March 1944: Japanese counterattack
General Hyakutake commanded about 40,000 men in his 17th Army, plus had at his disposal about 20,000 naval personnel in the Southern part under Vice Admiral Tomoshige Samejima. One of the units in Hyakutake's command, the 6th Infantry Division under Lieutenant General Masatane Kanda, was reputed to be the toughest in the army. Hyakutake did not become convinced until December 1943 of Allied intent to remain permanently at Torokina. The resulting delay in Japanese offensive action gave Griswold plenty of time to deploy his men in suitable defensive.
Hyakutake's attack on the Perimeter would employ the 12,000 men of the 6th Infantry plus 3,000 reserves. His faith in the ultimate victory was such that he planned on taking Griswold's surrender at the Torokina airstrip on 17 March. The Japanese dragged the greatest concentration of field artillery they had yet assembled onto the ridges overlooking the perimeter. Griswold knew that allowing the Japanese to hold these ridges was better than stretching his own lines thin by occupying them himself.
On the American side, Hodge's Americal Division and the Beightler's 37th Infantry Division manned the Perimeter, while the 3rd Marine Defense Battalion and 49th Coast Artillery Battalion (Army) protected the beachhead. Griswold had learned on New Georgia that waiting for the Japanese to attack was a much surer way to victory than undertaking his own offensive operations in a jungle.
The Battle of the Perimeter
As far as the press and the American public were concerned, the war had moved on from Bougainville. "The struggle for the Perimeter went almost unnoticed outside the Pacific."
Hyakutake opened his all-out effort to throw the Americans off Bougainville, which came to be known simply as The Counterattack, on 9 March, and his men succeeded in capturing Hill 700 and Cannon Hill; General Beightler's 37th Division recaptured these positions on the afternoon of 12 March. Griswold gave credit to the destroyers that provided bombardment of the Japanese positions, suppressing their attempts at reinforcement.
Hyakutake's second thrust was delayed until 12 March. The Japanese advanced through a deep ravine to approach the Piva Yoke fighter strip, and succeeded in penetrating the Perimeter at one point. General Beightler responded by sending combined tanks and infantry to drive them back. Also, Japanese artillery that had been bombarding all three American airstrips was silenced by AirSols bombers. This action ended on 13 March. Hyakutake attempted twice more to penetrate the perimeter, on 15 and 17 March, but was driven back both times. The Japanese mounted a final attack on the night of 23–24 March, which made some progress but was then thrown back. On 27 March, General Hodge's Americal Division drove the Japanese off of Hill 260, and the battle came to a close.
During the Battle of the Perimeter, Air Solomons continued plastering Rabaul completely reducing its offensive capability. "...AirSols delivered at least one strike on Rabaul every day that weather permitted. An average of 85 tons of bombs was dropped on the area daily from 20 February to 15 May – a total of 7,410 tons by almost 9,400 sorties.
The Japanese army, having taken heavy losses during these operations, withdrew the majority of its force into the deep interior and to the north and south ends of Bougainville.
On 5 April 1944, the Americal Division's 132nd Infantry Regiment, after establishing patrol sweeps along Empress Augusta Bay, successfully launched an attack to capture the Japanese-held village of Mavavia. Two days later, while continuing a sweep for enemy forces, the Regiment encountered prepared enemy defences, where they destroyed about 20 Japanese pillboxes using pole charges and bazookas. Later, the 132nd, together with elements of the Fiji Defence Force, was tasked with securing the heights west of Saua River. The regiment and its allies captured Hills 155, 165, 500, and 501 in fierce fighting that lasted until 18 April, when the last of the Japanese defenders were killed or driven off.
The Americans were reinforced by the 93rd Infantry Division, the first African American infantry unit to see action in World War II. The Allies concentrated on constructing multiple airfields in the beachhead, from which they conducted fighter and bomber operations over Rabaul, Kavieng and other Japanese-held bases in the South Pacific area. Air support over Bougainville was provided largely by the Royal New Zealand Air Force, the US Marine Corps aviation squadrons, and the United States Army Air Forces, under the control of AirSols.
The Japanese, isolated and cut off from outside assistance, primarily concentrated on survival, including the development of farms throughout the island.
Morale fell deplorably ... after the loss of the Battle of the Perimeter; Admiral Takeda, in his narrative, notes robberies, insubordination and even mutiny. Hundreds of soldiers deserted and wandered through the jungle, living on anything they could find, even on snakes, rats and crocodiles.
Australian intelligence officers, after studying records, estimated that 8,200 Japanese troops were killed in combat during the American phase of operations, and 16,600 more died of disease or malnutrition.
Second phase: November 1944 – August 1945
Between October and December 1944, the U.S. ground forces handed over operations on the island to the main body of the Australian II Corps, a Militia formation. The Australian 3rd Division and the 11th Brigade were on Bougainville, reinforced by the Fiji Infantry Regiment. The 23rd Brigade garrisoned neighbouring islands. The Australians determined that Japanese forces on Bougainville, now numbering approximately 40,000, still had approximately 20 percent of their personnel in forward positions and that although understrength, were organized in combat-capable formations, including the 38th Independent Mixed Brigade and the 6th Division. The Australian II Corps, commanded by General Stanley Savige, adopted an aggressive posture to overwhelm and reduce or destroy these forces.
So began the second phase of the Allied campaign. Opening combat as early as 29 November and the offensive on 30 December, three separate drives developed: in the north, it was planned that Japanese forces would be forced into the narrow Bonis Peninsula and contained; in the centre the seizure of Pearl Ridge would give the Australians control of the east–west thoroughfares and protection against further counterattacks, while also opening the way for a drive to the east coast; and the main campaign in the south, where the bulk of the Japanese forces were concentrated at Buin.
Following the capture of Pearl Ridge in the central sector in December 1944, the focus of the Australian campaign moved to the northern and southern sectors, with operations in the central sector being confined to patrols along the Numa Numa trail. In the north the Australians advanced along the coast towards the Genga River while sending patrols inland to flush the Japanese out of the high ground. After capturing Tsimba Ridge in February 1945 they continued to advance on Ratsua, forcing the Japanese into the Bonis Peninsula. Coming up against formidable defences, however, an attempt was made to outflank the Japanese positions by landing an amphibious force at Porton Plantation in June, however, this failed and as a result it was decided to suspend the drive into the Bonis Peninsula and instead contain the Japanese along the Ratsua front while resources were diverted to the southern sector for the drive towards Buin. In the southern sector, after a brief but costly counterattack by the Japanese at Slater's Knoll, the Australians had managed to gain the upper hand and advanced steadily to the south, crossing the Hongorai, Hari and Mobai Rivers. However, shortly after reaching the Mivo River their advance came to a halt as torrential rain and flooding washed away many of the bridges and roads upon which the Australian line of communications was dependent. This rendered large scale infantry operations impossible for almost a month and it was not until late July and into early August that the Australians were able to resume patrolling across the Mivo River.
Combat operations on Bougainville ended with the surrender of Japanese forces on Bougainville on 21 August 1945. The Empire surrendered in Tokyo Bay on 2 September 1945. The last phase of the campaign saw 516 Australians killed and another 1,572 wounded. 8,500 Japanese were killed at the same time, while disease and malnutrition killed another 9,800 and some 23,500 troops and labourers surrendered at the end of the war.
Three Victoria Crosses were awarded during the campaign, one to a Fijian and two to Australians. Corporal Sefanaia Sukanaivalu of Fiji received the award posthumously for his bravery at Mawaraka on 23 June 1944. Corporal Reg Rattey received the award for his actions during the fighting around Slater's Knoll on 22 March 1945, while Private Frank Partridge earned his in one of the final actions of the campaign on 24 July 1945 during fighting along the Ratsua front. Partridge was the only member of the Militia to receive the VC which was the last of the war to an Australian.
- Figure includes deaths from all causes: combat, disease, starvation, and accident. The Australians counted 21,000 to 23,500 Japanese survivors on Bougainville upon the surrender of Japanese forces at the end of World War II. If Gailey's and Long's figure of 65,000 Japanese troops originally on Bougainville is accurate, then the Japanese casualty figures would be far higher. Long's figures are quoted in the narrative, totalling 16,700 combat deaths and 26,400 deaths from disease and malnutrition.
- Rottman provides the figure of 45,000 while Gailey and Long state that there were 65,000 total Japanese personnel in and around Bougainville. Long's estimate is that of contemporary Australian intelligence officers, which he says was verified at the end of the war.
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|Wikimedia Commons has media related to Bougainville_campaign_(1943-45).|
- James, Karl (2012). The Hard Slog: Australians in the Bougainville Campaign, 1944–45. Port Melbourne, Victoria: Cambridge University Press. ISBN 978-1-107-01732-0.
- Medcalf, Peter (2000). War in the Shadows: Bougainville 1944–1945. Brisbane, Queensland: University of Queensland Press. ISBN 978-0-702-23144-5.