Strategic situation By late 1943 and early 1944, Australian and US forces had begun offensive actions in New Guinea, having stemmed the tide of the Japanese advance during the fighting in 1942. In September 1943, the Allies had secured
Lae and
Nadzab with simultaneous advances from the
7th and
9th Divisions. Shortly afterwards, the 9th Division had landed on the
Huon Peninsula and had subsequently secured
Finschhafen and began clearing inland. By October 1943, the next objective for the Australians was
Shaggy Ridge, a series of high positions on the inland route from Dumpu to
Madang, which was held by Japanese infantry, supported by artillery and engineers. As part of this advance the
7th Division set out through the Ramu Valley into the
Finisterre Range, during which a series of minor engagements were fought, including those around
John's Knoll and Trevor's Knoll, as the Japanese withdrew to their main defensive line, which was centred around the Kankiryo Saddle and Shaggy Ridge. Shaggy Ridge was a long spur dotted by several rocky outcrops, which the Australians dubbed "Green Pinnacle", "The Pimple", "Green Sniper's Pimple" and "McCaughey's Knoll". To the north and north-west of Shaggy Ridge, two high features were identified as "Prothero I" and "Prothero II", while the Kankiryo Saddle to the north-east joined Faria Ridge and divided the Faria River from the
Mindjim River. 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. The ridge dominated the area around it, standing at , and in clear weather offered observation as far north as Madang, although largely the area was covered in thick fog which greatly reduced visibility. The sheer nature of the terrain meant that there was only a single track along the ridge line which was, and according to author Lachlan Grant, "in places...only wide enough for one man to pass with sheer drops on either side".
Opposing forces The area was defended by elements of the Imperial Japanese Army's
78th Infantry Regiment, supported by the 26th Artillery Regiment and the 27th Independent Engineer Regiment, which formed part of a detachment under the command of Major General
Masutaro Nakai, who was subordinated to the
18th Army. These units were roughly at half strength, although Australian intelligence estimates put the number of troops around Kankiryo and Shaggy Ridge at around 3,000. Against this, the Australian forces were drawn from the 7th Division, which due to limited resources only pushed two brigades forward at any one time; initially these were the
21st and
25th Brigades, although they were later replaced by the
15th and
18th Brigades. These forces would subsequently rotate throughout the fighting. With the exception of the 15th Brigade, which was a
Militia formation, these were all
Second Australian Imperial Force units. These elements were supported by artillery from the
2/4th Field Regiment, equipped with eleven
Ordnance QF 25-pounders and 7,000 rounds, and aircraft from the
Royal Australian Air Force and
United States Army Air Force.
Assault on the Pimple In late December 1943, the Australian offensive to take Shaggy Ridge began, focused on an attack on The Pimple. The Pimple was one of three rocky outcrops, held by the Japanese on the ridge line. The
2/16th Battalion of the Australian 21st Brigade had been reinforced with hundreds of new troops, after earlier losses. It proceeded up the southern slopes towards The Pimple, with air support. The area was bombarded with a preparatory artillery and aerial barrage. The attack was successful, driving the Japanese off the position on 27–28 December 1943. Australian troops held it against further counter-attacks, and further attacks were followed up against the other positions. This allowed the Australians to gain a foothold on the position, and in the process they gained a position that had been holding them up for the past two months; nevertheless, the Japanese continued to hold Shaggy Ridge in strength. ==Battle==