A central geographical and strategic feature of these campaigns was the imposing Shaggy Ridge, running north–south in the Finisterres; this was the scene of a climactic battle during which the Australians assaulted the Japanese positions in December 1943 and January 1944.

During September 1943, Australian forces from Major General George Vasey's 7th Division, advancing from Nadzab, had captured Lae, as part of a pincer undertaken in conjunction with Major General George Wootten's 9th Division, which had advanced along the coast from the east of Lae.

Heavy rain had held up the Australian advance and much of the garrison had managed to withdraw inland, prior to the capture of the town.

[1] It faced the Australian 7th Division, consisting of approximately 17,000 men,[4] under Vasey, and made up of the 18th, 21st and 25th Brigades, along with the 2/6th Commando Squadron.

[7] This threat manifested itself in the road that the Japanese were attempting to build from Madang on the coast inland to Nadzab, via Bogadjim, along which they were hoping to advance through to Dumpu.

For the Japanese, it provided a strong obstacle to the Australian advance north towards the coast, while also offering them the ground along which they could launch their own offensive in order to recapture the territory they had lost earlier in the campaign.

[5] In November, the 25th Brigade relieved the 21st as the offensive was maintained,[7] and later in December and into January heavy fighting took place around Shaggy Ridge,[5] a 6.5-kilometre (4.0 mi) long spur dotted by several rocky outcrops.

The Japanese had established numerous strong posts and positions along the ridge, blocking the Australian advance towards the coast, where they were aiming to secure Bogadjim and Madang.

[14] The 2/4th Field Regiment, which established its guns around the Lake area to the west of the Mosia River, and south of Guy's Post, while stores were brought up to that position by jeep.

[18] As the Australians began consolidating their position, the 7th Division was ordered to limit its exploitation, while supplies were pushed forward of Kankiryo.

Meanwhile, in an effort to harass the Japanese rearguard, the 57th/60th Infantry Battalion undertook a program of long range patrols to the north.

A few days later, the 11th Division, under the command of Major General Allan Boase took over from the 7th, and they subsequently linked up with US forces on the coast around Rimba as they pushed forward along an axis bounded by the Kabenau and Nuru Rivers.