38th Independent Mixed Brigade The Battle of Pearl Ridge (30–31 December 1944) was an engagement 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.

The Japanese had captured Bougainville in early 1942, and had subsequently built it into a significant base with large numbers of aircraft and troops, in order to protect the fortress at Rabaul.

[5] Although understrength, these troops were reported to still be capable of conducting effective combat operations and continued to pose a threat to the Allied base at Torokina.

As such, in mid-December, after a period of information gathering,[6] it was decided that the Australian II Corps, consisting of Militiamen from the 3rd Division and the 11th Brigade would go on the offensive.

[12] For several days, the Australian battalion commander formulated a plan to capture Pearl Ridge, possession of which would enable the Australians to block Japanese attempts to approach the main Allied base around Torokina, and would disrupt the movement of Japanese troops along the north–south axis of the island, hindering their ability to reinforce isolated pockets.

[10] Believing that the ridge was held by two understrength companies from the Japanese 81st Infantry Regiment—approximately 80–90 men—who had withdrawn there after the fighting on Little George and Artillery Hill, the Australians decided to commit only a battalion to capture it.

[11] On the morning of 30 December, after 40 minutes of airstrikes from Royal New Zealand Air Force Corsairs, who had been guided onto their targets by RAAF Boomerangs,[3][10] the roughly 800-strong 25th Battalion carried out an attack supported by artillery and machine gun fire with four companies advancing across a 1,000-yard (910 m) frontage stretching across the ridge.

Unbeknown to the Australians, however, the two companies from the 81st Infantry Regiment had been reinforced by men from the Japanese 38th Independent Mixed Brigade under Major General Kesao Kijima and they actually numbered 550.

[15] Although the left-most Australian company—'C' Company under Captain Wallace Bruce, advancing from Werda's Knoll—managed to reach the ridge pushing through thick bamboo and killing several Japanese, due to the terrain Lieutenant Bruce Shaw's 'A' Company, on the far right of the Australian line and having stepped off from Artillery Hill, 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 from the north-east from a feature dubbed "Pear Hill".

Although it required a more physically draining approach march over Artillery Hill and through dense scrub, the tactic proved to be more successful than the previous day's efforts.

Pear Hill was joined by a narrow razorback ridge that limited the Australian frontage to just three men side-by-side, who had to cut their way through the thick bamboo with machetes.

[16] By late afternoon, the Japanese defenders had pulled back from the ridge, leaving the Australians in possession of it after heavy fighting with 'D' Company securing the main position, while 'B' Company skirted north of Barton's Knoll and secured a secondary position below the ridge, which the Australians dubbed Baker's Brow.

[13] James attributes this to the limited infrastructure in the area, and the lack of defensive construction or development undertaken following the Japanese capture of the island in 1942.

[19] Following the battle of Pearl Ridge, the Australians launched a full-scale offensive to counter the Japanese resistance on the island, focused on the southern sector.

The 11th Brigade, under Brigadier John Stevenson, then took control of both the central and northern sectors in order to free up troops for the main offensive in the south, and the brigade subsequently cycled its three infantry battalions through the position, while pursuing a limited advance in the north, attacking Tsimba Ridge in January – February 1945 after advancing along the coast from Kuraio Mission.

The rate of effort required to bring stores forward was of significant concern to the Australian corps commander, Lieutenant General Stanley Savige, to the extent that his orders to the commander of the 11th Brigade stipulated no further advances in the sector, with the exception of patrolling to prevent the movement of Japanese reinforcements towards the south, and for information gathering purposes.