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With the relief of the Americans by the Australians, the campaign on Bougainville assumed a more positive character. For the Americans, the island had not been an objective in itself but a stepping stone in the advance northward, and their land operations were limited to ensuring the integrity of the Empress Augusta Bay base. The task of the 2nd Australian Corps, on the other hand, was the reconquest of the island.

The campaign developed into three separate drives. To the north, the enemy was to be pushed up the west coast to the Bonis Peninsula and contained there until he could be starved out or destroyed. Inland from Torokina, the Australians were to push along the Numa Numa trail to Pearl Ridge, in the centre of the island, possession of which would give protection against attack from the east and a jumping-off place for operations against the Japanese east coast bases. Southward, the plan was to occupy the coastal lowlands and eventually bring the enemy to action in the Buin area, where his major forces were concentrated and where the decisive battles of the campaign would be fought. It was in support of these operations, in addition to the continuous pounding of Rabaul and New Ireland, that the RNZAF operated during the last ten months of the war.

The first actions fought by Australian troops on Bougainville were on the Numa Numa trail. On 29 November elements of the 9th Battalion, which had relieved the Americans in the Doiabie Valley on the 23rd, took a Japanese position which was blocking their path at Piaterapaia. Three weeks later E Company of the battalion captured Artillery Ridge, the last high feature before Pearl Ridge. On New Year's Eve Pearl Ridge itself was occupied after a two-day battle by the 25th Battalion (7th Brigade), which had taken over from the 9th Battalion.

During these operations RNZAF fighters several times gave close support to the infantry, a role which was to become increasingly important in the months to come. On 7 December eight aircraft of No. 15 Squadron, led by Squadron Leader Winstone,¹ were ordered page 292 to attack a Japanese position which was holding up the troops in their advance from Piaterapaia. The objective was a group of five huts, dispersed over an area of fifty yards square on the top of a hill. The Corsairs were led in by two Boomerangs of No. 5 Tactical Reconnaissance Squadron, RAAF, which had previously reconnoitred the area. The Boomerangs marked the target by strafing it, and the Corsairs, after a preliminary run over, dived and dropped their bombs from 800 feet. The huts were destroyed, along with an estimated thirty to forty Japanese, and an area of 150 yards of tall scrub was flattened.

The bombs were 325-pound depth-charges. They had not been used before against land targets on Bougainville, but experience by RAF squadrons in Burma had shown that they were ideal for jungle bombing. They burst on impact, making no crater, and produced a very strong lateral blast which destroyed all cover within a considerable radius.

Another strike was made in the same region the following week. The Australians were to attack Japanese troops entrenched on a hillside half a mile south of Retsiopaia, and eight aircraft of No. 15 Squadron, each carrying a depth-charge or a 500-pound bomb, went in first to soften up the position.