Bougainville Campaign The Bougainville campaign ( Operation Cherry Blossom ) was fought by the Allies in the South Pacific during World War II to regain control of the island of Bougainville from the Japanese forces who had occupied it in 1942 . 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 New Guinea , while allowing continued expansion to the south - east , down the Solomon Islands chain , to Guadalcanal . The Allied campaign , which had two distinct phases , began on 1 November 1943 and ended on 21 August 1945 , with the surrender of the Japanese . 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 . As a result , the campaign is referred to as part of both the New Guinea and the Solomon Islands campaign s . Japanese occupation . 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 . Allied offensives . First phase : November 1943 – November 1944 . Following the American success at Guadalcanal in February 1943 , Allied forces advanced up the Solomon Island chain and in late 1943 commenced the Bougainville campaign as part of the larger Operation Cartwheel . 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 . The first phase of Allied operations to retake Bougainville ( Operation Cherry Blossom ) from the Japanese 17th Army began with landings at Cape Torokina by the U . S . Marine 3rd Division , I Marine Amphibious Corps , on 1 November 1943 . The Allies established a beachhead around Cape Torokina for the construction of an airfield within fighter range of Rabaul . Allied forces did not plan at this time to try to capture the entire island of Bougainville from Japanese forces . An attempt by the Imperial Japanese Navy to attack the U . S . landing forces was defeated by the U . S . Navy in the Battle of Empress Augusta Bay , on 1 – 2 November . A subsequent attempt by Japanese land forces to attack the Allied beachhead was defeated in the Battle of Koromokina Lagoon . From 6 – 19 November 1943 the I Marine Amphibious Corps landed the remaining regiment of the 3rd Marine Division and the U . S . Army ' s 37th Infantry Division to expand the beachhead . Protracted and often bitter jungle warfare followed , 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 , with the following battles taking place during this time : Koiari Raid , Piva Trail , Coconut Grove and Piva Forks . 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 . 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 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 1943 , the I Marine Amphibious Corps was replaced by the Army ' s XIV Corps and on 28 December , the 3rd Marine Division by the Americal Division . The XIV Corps defended the beachhead against a major Japanese counterattack from 9 – 17 March 1944 , at Hill 700 and Cannon Hill , which were defended by the Ohio 37th Infantry Division , and Hill 260 , which was defended by the Americal Division . The counterattack was defeated with heavy losses for the Japanese army , which then 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 charge s and bazooka s . 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 Japanese , isolated and cut off from outside assistance , primarily concentrated on survival , including the development of farms throughout the island . 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 USAAF , under the control of Air Command , Solomons ( AIRSOLS ) . 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 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 Cross es 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 . Namesake . The U . S . Navy escort aircraft carrier USS " Bougainville " ( CVE - 100 ) , in commission from 1944 to 1946 , was named for the Bougainville campaign .