December 30, 1944 – The Battle of Pearl Ridge was a battle of the Second World War fought between Australian and Japanese forces on Bougainville Island. Part of the wider Bougainville Campaign, the battle took place in the central sector of the island, shortly after the Australians had taken over responsibility from the Americans. Believing that the ridge was held by less than a company of Japanese, on 30 December the Australian 25th Battalion launched a four-pronged attacked the ridge. The defending force, however, had been greatly reinforced and was closer to a battalion in strength. After being held up on the right of their advance, the Australians dug in overnight and repulsed a strong Japanese counterattack before resuming the attack on 31 December. By late in the afternoon, the Japanese had been swept off the ridge. Believing that the ridge was held by two understrength companies from the Japanese 81st Infantry Regiment—approximately 80–90 men—it was decided to commit only a battalion to capture it. On the morning of 30 December, after 40 minutes of airstrikes, the 25th Battalion carried out an attack supported by artillery and machine gun fire with four companies advancing across a 1,000 yd (910 m) frontage stretching across the ridge. Unbeknown to the Australians, however, the two companies from the 81st Infantry Regiment had been reinforced by 550 men from the Japanese 38th Independent Mixed Brigade under Major General Kesao Kijima and they had heavily fortified the ridge with up to six artillery pieces and between 20–30 mortars. Although the left-most Australian company managed to reach the ridge, due to the terrain the company on the far right of the Australian line was forced into advancing across a narrow razorback only 12 ft (3.7 m) wide, along which the Japanese were able to concentrate a significant amount of fire which prevented the Australians from moving forward. As more artillery fire was brought down on the ridge in support of the attack, an attempt was made to outflank the Japanese position in front of the razorback, although these too proved unsuccessful and after the Australians had suffered a number of casualties the attack on the right was called off and the company ordered to form a defensive position and await further orders. The Australian commander, McKinna, then ordered the two companies in the centre to dig in where they were, while the left-most company, which had reached the Japanese track on the northeastern side of the ridge would also dig in and attempt to hold its position until daybreak. During the night the Japanese counter-attacked. They were, however, repulsed and the following day the Australians resumed their attack. By late afternoon, the Japanese defenders had pulled back from the ridge, leaving the Australians in possession of it and with it a vantage point from where they could see from one side of Bougainville to the other During the course of the battle, the Australians lost 10 killed and 25 wounded, while 34 Japanese bodies were found around the position and one prisoner taken.