Battle of Pearl Ridge



The Battle of Pearl Ridge (30–31 December 1944) 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.

Background
Advanced Australian elements began arriving on Bougainville in September and by November–December 1944 four brigades from the Australian II Corps took over responsibility for Bougainville from the divisions of US XIV Corps that had been stationed there previously. At the time, it was believed that the Japanese forces on the island numbered around 17,500 men —although intelligence reports and estimates on this matter varied greatly and indeed after the war it was found that there had been more than 40,000 at the time—and although understrength the Allies believed that the Japanese formations in the area were still capable of carrying out effective combat operations. In order to counter this, it was decided that the Australian II Corps, consisting of the 3rd Division and the 11th Brigade would go on the offensive and a three pronged campaign was planned in the northern, central and southern sectors of the island.

Initially, the 7th Brigade was given responsibility for the central sector, and in November it began operations to clear the Japanese from the high features in the sector. On 23 November, the Australian 9th Battalion captured a Japanese outpost on a feature known as Little George, before taking part in the capture of Artillery Hill in mid December.

Shortly after this, the Australian 25th Battalion—under Lieutenant Colonel John McKinna—relieved the 9th Battalion at Artillery Hill and began patrolling operations towards the Japanese position on Pearl Ridge, a feature which due to its height offered commanding views of the entire island.

Battle
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 1000 yd 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 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.

Aftermath
Following the battle of Pearl Ridge, the Australians launched a full scale offensive to counter the Japanese resistance on the island. As a result of this decision, the 7th Brigade was moved from the central sector to the southern sector, where the majority of the Japanese forces were located. The 11th Brigade then took control of both the central and northern sectors in order to free up troops for the main offensive in the south. The brigade maintained a battalion-group element on the ridge during this phase and carried out extensive patrols forward of the position, while artillery was brought up to the foot of the Laruma escarpment from where they could fire on Japanese positions under the control of forward observers on Pearl Ridge.

Due to the terrain around the ridge, many resources were used to bring in supplies and so in an effort to improve the Australian line of communications in the sector, engineers from the 16th Field Company constructed a road using a bulldozer that had to haul itself up the ridge via a steel cable that was manhandled up to a point just below the ridge over the course of eight days.

After the war, the 25th Battalion was awarded the battle honour of "Pearl Ridge" for the battle. Today this honour is maintained by the 25th/49th Battalion, Royal Queensland Regiment.