page_title: Battle of Tsimba Ridge
section_title: Aftermath
hierarchical_section_title: Battle of Tsimba Ridge / Aftermath
caption_attribution_description: English: Soldiers from the Australian 31st/51st Infantry Battalion patrol around Tsimba Ridge after the fighting to capture that position
context_page_description: The Battle of Tsimba Ridge was an engagement of the Second World War involving Australian and Japanese forces. Part of the wider Bougainville Campaign of the Pacific theatre, the battle occurred in the northern sector of Bougainville Island between 17 January and 9 February 1945, when the lead battalion of the Australian 11th Brigade—the 31st/51st Infantry Battalion—advanced towards the Genga River as part of a drive north to the Bonis Peninsula.
  On the peninsula, an enclave of Japanese troops had established itself after withdrawing north following earlier engagements in the centre of the island throughout 1944–45. Coming up against heavy resistance along Tsimba Ridge, the Australians' advance was halted for three weeks as they fought to wrest control of the ridge from the defending Japanese from the 81st Infantry Regiment, whose strength was roughly equal to that of the Australians. The main Australian attack took place on 6 February, but it was not until 9 February that the Japanese completely withdrew from the position. Small-scale fighting in the surrounding area continued until 22 February.
context_section_description: Fighting around the Genga River continued for the next couple of days, with clashes occurring until the Australians had cleared the northern and southern banks by 11 February, during which time Japanese artillery opened up on the Australians, causing several casualties. In securing the ridge, the Australians captured a large amount of Japanese equipment, including four field and six anti-tank guns, nine machine guns and 86 rifles. Japanese casualties were estimated at 66 killed, while Australian casualties in the Tsimba area were 12 killed and 20 wounded. Within the context of the campaign, these losses were considered heavy by the Australians, and an Australian newspaper report from shortly after the battle described it as the "bloodiest battle of the campaign", while another described it as "fiercest" fought on Bougainville up to that point.  From documents captured after the war, it was shown that the Japanese believed that these losses would slow the Australian advance. At the time they did not perceive the loss of Tsimba Ridge to be a defeat. They had been prepared to hold the position, and had the numbers to do it; however, Nakamura had decided to withdraw from the ridge when the morale of his troops had fallen due to lack of ammunition and food, and rising casualties from tropical diseases. The real size of the force holding Tsimba Ridge was also revealed by documents captured after the war, highlighting the gross underestimation of Japanese strength by Australian intelligence sources.
  After the fall of Tsimba Ridge, fighting continued around the Genga River for the next couple of weeks. By 10 February the area south of the Genga had been cleared of Japanese and the Australians began to patrol along the northern bank. Several minor clashes occurred, the most serious of which saw three Japanese killed and three Australians wounded when the Australians managed to capture a Japanese 37 mm gun. As the Japanese were forced to withdraw from a position along the track which ran 150 yards (140 m) from the river, the Japanese artillery intensified and several men from the 31st/51st Infantry Battalion became casualties.
  The 31st/51st Infantry Battalion continued operations around the Genga River until 26 February, by which time three companies had reached the Gillman River, while another had struck inland, fighting a short engagement around Kunamatoro, before pressing on towards a ridge near the Soraken Plantation. Throughout the final weeks of February, 'A' Company of the 31st/51st, under Downs, fought the Japanese defenders off the position, which was subsequently named "Downs' Ridge" by the Australians. On 26 February, the 31st/51st was relieved by Lieutenant Colonel Bernard Callinan's 26th Infantry Battalion, who continued the advance north towards the Soraken Peninsula, while the 55th/53rd Infantry Battalion advanced on Ratsua as the Australians sought to establish a defensive line across the base of the Bonis Peninsula between Ratsua and Ruri Bay. The 31st/51st would later take part in the failed landing at Porton Plantation in June, where they would suffer heavy casualties, including Downs, who was killed leading his company. In total, the Australians lost 34 killed and 91 wounded in the fighting around the Genga River, while it was estimated that the Japanese lost 148 killed. For its involvement in taking Tsimba Ridge, the 31st/51st Infantry Battalion was awarded the battle honour "Tsimba Ridge".
caption: Soldiers from the Australian 31st/51st Infantry Battalion patrol around Tsimba Ridge after the main fighting, 17 February 1945
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