The 'Campaign for Eastern New Guinea' was a series of actions fought between the Allied and Japanese forces as part of the in the New Guinea campaign and in succession to the 'Campaign for Eastern Papua' (22 April/16 September 1943).

In this campaign, Australian and US forces sought to capture two major Japanese bases, one in the town of Lae and the other at Salamaua. The campaign to take the Salamaua and Lae area began after the successful defence of Wau in late January, which was followed up by an Australian advance toward Mubo as the Japanese force which had attacked Wau withdrew to positions around Mubo. A series of actions followed over the course of several months as Major General S. G. Savige’s Australian 3^rd Division advanced to the north-east in the direction of Salamaua. After an amphibious landing at Nassau Bay, the Australians were reinforced by a US regimental combat team, which subsequently advanced to the north along the coast.

As the Allies maintained the pressure on the Japanese around Salamaua, early in September they launched an airborne assault on Nadzab, and a seaborne landing near Lae, subsequently taking the town with simultaneous drives from the east and north-west. As the situation around Lae grew more desperate, the Salamaua garrison withdrew and the town was captured on 11 September 1943, while Lae fell shortly after this on 16 September, bringing the campaign to an end.

In March 1942, the Japanese had secured Salamaua and Lae and subsequently established major bases on the northern coast of New Guinea, in the large town of Lae and also in Salamaua, a small administrative town and port 22 miles (35 km) to the south. Salamaua was a staging post for attacks on Port Moresby, such as the Kokoda Track campaign, and a forward operating base for Japanese air power. When the attacks failed, the Japanese turned the port into a major supply base. Logistical limitations meant that the area of Salamaua and Lae area could accommodate only some 10,000 Japanese personnel in the form of 2,500 seamen and 7,500 soldiers. The defences were centred on the 'Okabe' Detachment, a brigade-sized force from Lieutenant General Hidemitsu Nakano’s 51^st Division under the command of Major General Toru Okabe.

In January 1943, the 'Okabe' Detachment was defeated in an attack on the Australian base of Wau, about 25 miles (40 km) away. Allied commanders then turned their attention to Salamaua, which could be attacked by troops flown into Wau. This also diverted attention from Lae, which was a major objective of 'Cartwheel', the Allied grand strategy for the South Pacific. It was decided that the Japanese would be pursued toward Salamaua by the Australian 3^rd Division, which had been formed at Wau under Savige’s command, and which was to link with elements of Major General Horace H. Fuller’s US 41^st Division.

After the end of the fighting around Wau late in January, the 'Okabe' Detachment had pulled back toward Mubo, where its started to regroup with a strength of about 800 men. Between 22 April and 29 May 1943, the Australian 2/7^th Battalion, at the end of a long and tenuous supply line, attacked the southern extremity of Japanese lines in the Mubo area, at features known to the Allies as 'The Pimple' and 'Green Hill'. While the 2/7^th Battalion made little progress, it provided a diversion for Major G. Warfe’s 2/3^rd Independent Company, which advanced in an arc and raided Japanese positions at Bobdubi Ridge, inflicting severe losses. In May, the 2/7^th Battalion repelled a number of strong Japanese counterattacks.

At the same time as the '1^st Battle of Mubo', the Australian 24^th Battalion, which had been defending the Wampit river valley in an effort to prevent Japanese movement into the area from Bulolo, detached several platoons to reinforce the 2/3^rd Independent Company. During May, they were heavily engaged in patrolling the 3^rd Division’s northern flank, around the Markham river, and the area around Missim, and one patrol succeeded in reaching the mouth of the Bituang river to the north of Salamaua.

In response to the Allied moves, the commander of the Japanese 18^th Army, Lieutenant General Hatazo Adachi, sent the 66^th Regiment from Finschhafen, at the eastern end of the Huon peninsula, to reinforce the 'Okabe' Detachment and launch an offensive. About 1,500 men strong, the 66^th Regiment attacked at Lababia Ridge on 20/23 June. The 'Battle of Lababia Ridge' has been described as one of the Australian army’s classic engagements of World War II. The ridge’s only defenders were the men of D Company of the 2/6^th Battalion. The Australians relied on well-established and linked defensive positions, featuring extensive, cleared free-fire zones. These and the determination of D Company defeated the Japanese envelopment tactics.

Between 30 June and 19 August, Brigadier H. H. Hammer’s Australian 15^th Brigade cleared Bobdubi Ridge in the '2^nd Battle of Bobdubi'. The operation was opened with an assault by the inexperienced 58^th/59^th Battalion, and included hand-to-hand combat. At the same time as the second Australian assault on Bobdubi, on 30 June/4 July, the US 162^nd Regimental Combat Team, supported by engineers of Brigadier William F. Heavey’s 2^nd Engineer Special Brigade, made an unopposed amphibious landing at Nassau Bay and established a beach-head from which to launch a drive along the coast, as well as bringing ashore heavy guns with which to reduce the Japanese positions.

One week after the Bobdubi attack and Nassau Bay landing, Brigadier M. J. Moten’s Australian 17^th Brigade launched another assault on Japanese positions at Mubo, and with the Allies making ground closer to Salamaua, the Japanese withdrew to avoid encirclement. Nakano, the Japanese divisional commander, subsequently decided to concentrate his forces in the Komiatum area of high ground to the south of Salamaua.

Meanwhile, the main body of the 162^nd Regimental Combat Team followed a flanking route along the coast, before encountering fierce resistance in the 'Battle of Roosevelt Ridge', so named for Lieutenant Colonel Archibald Roosevelt, commander of the 3/162^nd Regimental Combat Team, between 21 July and 14 August. Between 16 July and 19 August, the 42^nd and 2/5^th Battalions gained a foothold on Mount Tambu. They held on despite fierce Japanese counterattacks in the 'Battle of Mt Tambu'. The battle turned when the Australians started to receive support from the 162^nd Regimental Combat Team. Throughout July, the Japanese sought to reinforce the Salamaua area, drawing troops away from Lae; by the end of the month there were around 8,000 Japanese around Salamaua.

On 23 August, Savige and the 3^rd Division handed over the Salamaua operation to the Australian 5^th Division under Major General Edward J. Milford. Throughout the period between late August and early September, the Japanese in the Salamaua region fought to hold the advancing Allies along their final line of defence in front of Salamaua, but the 58^th/59^th Battalion was able to cross the Francisco river and the 42^nd Battalion subsequently captured the main Japanese defensive position around 'Charlie Hill'. After Allied landings near Lae in the first week of September, Adachi, the 18^th Army commander, ordered Nakano to abandon Salamaua, and Nakano’s units subsequently withdrew to the north disinvesting the town and transferring between 5,000 and 6,000 troops by barge, while other troops marched out along the coastal road. The 5^th Division subsequently occupied Salamaua on 11 September, securing its airfield.

The fighting between April and September in the Salamaua region had cost the Australians 1,083 casualties, including 343 dead. The Japanese had lost 2,722 killed and a further 5,378 wounded, for a total of 8,100 casualties. The US 162^nd Regimental Combat Team lost 81 men killed and 396 wounded. Throughout the fighting, Allied aircraft and US PT-boats supported the troops ashore, enforcing a blockade of the Huon Gulf and the Vitiaz and Dampier Straits.

The main operation to take Lae was 'Postern'. Planned as part of wider operations to secure the Huon peninsula, the operation was planned under the supervision of General Sir Thomas Blamey, who assumed command of the Allied New Guinea Force, and the Australian I Corps' commander, Lieutenant General Sir Edmund Herring. The planned undertaking took the form of a classic pincer movement with comparatively novel elements, involving an amphibious assault to the east of the town, and an airborne landing near Nadzab, 32 miles (50 km) to its west. The battle casualties of Major General G. F. Wooten’s Australian 9^th Division during 'Postern' amounted to 547 men, of whom 115 were killed and 73 were posted as missing, and 397 wounded, while Major General G. A. Vasey’s Australian 7^th Division suffered 142 casualties, of whom 38 were killed. The Japanese lost about 1,500 killed, while a further 2,000 were taken prisoner.

On 4 September, the Australian 9^th Division came ashore to the east of Lae, on two beaches near Malahang, at the start of the attempt encircle Japanese forces in the town. Five US Navy destroyers provided fire support. The landings were not opposed by Japanese land forces but were attacked by Japanese bombers, which inflicted numerous casualties among the naval and military personnel on board several landing craft. Brigadier W. J. V. Windeyer’s Australian 20^th Brigade led the assault, with Brigadier D. A. Whitehead’s Australian 26^th Brigade following it, while Brigadier B. Evans’s Australian 24^th Brigade formed the divisional reserve. The 9^th Division faced formidable natural barriers in the form of rivers swollen by recent rain, and thus came to a halt at the Busu river, which could not be bridged as the division lacked heavy equipment, and the far bank was occupied by the Japanese. On 9 September, the 2/28^th Battalion led the attack across the Busu river and secured a bridgehead after fierce fighting.

On the following day, the US 503^rd Parachute Infantry Regiment, together with two gun crews from the Australian 2/4^th Field Regiment, who had received a crash course in the use of parachutes,and their cut-down 25-pdr gun/howitzers, made an unopposed parachute drop at Nadzab, just to the west of Lae. The airborne forces secured Nadzab airfield, so that Vasey’s Australian 7^th Division could be flown in and prevent any possible Japanese retreat into the Markham river valley. The 7^th Division suffered its worst casualties of the campaign on 7 September, as it was boarding aircraft at Port Moresby: a Consolidated B-24 Liberator four-engined heavy bomber crashed while taking off, hitting five trucks carrying members of the 2/33^rd Battalion: 60 men died and 92 were injured.

On 11 September, Brigadier K. W. Eather’s Australian 25^th Brigade of the 7^th Division engaged about 200 Japanese soldiers entrenched at Jensen’s Plantation in a firefight at a range of 45 yards (50 yards), with the 2/4^th Field Regiment providing artillery support. After defeating the Japanese and killing 33 of them, the 25^th Brigade engaged and defeated a larger Japanese force at Heath’s Plantation, killing 312 Japanese soldiers. The 25^th Brigade entered Lae on 15 September, just before the 9^th Division’s 24^th Infantry Brigade, and the two units linked on that day.

While the fall of Lae was clearly a victory for the Allies, and was achieved more quickly and at lower cost than had been anticipated, a significant proportion of the Japanese garrison had escaped through the Saruwaged mountain range to the north of Lae, and would have to be fought again elsewhere. The Huon peninsula campaign was the result, and a quick follow-up landing was subsequently undertaken by the 20^th Brigade.

Despite initial plans to do so, Salamaua was not developed as a base. Herring, the Australian I Corps' commander, visited Salamaua by PT-boat on 14 September, three days after its capture, and found little more than bomb craters and corrugated iron. He recommended cancelling the development of Salamaua and concentrating all available resources on Lae. The base that had originally been envisaged now looked like a waste of effort, because Salamaua was a poor site for a port or air-base. However, in drawing the Japanese attention away from Lae at a critical time, the assault on Salamaua had already served its purpose.

Lae, on the other hand, was subsequently transformed into two bases: the Australian Lae Base Sub Area and a US Services of Supply base. Herring combined the two as the Lae Fortress under Milford’s command. Because Blamey had launched 'Postern' before the logistical preparations were complete, most of the units needed to operate the base were not yet available.

The importance of Lae as a port was to supply the air base at Nadzab, but this was compromised by the fact that the Markham river valley road was found to be in poor condition. To expedite the development of Nadzab, minimal efforts were made to repair it, but heavy military traffic bound for Nadzab was permitted to use it. The road was closed following heavy rains on 7 October and did not reopen until December. Until then, Nadzab had to be supplied by air, and its development was slow because heavy engineer units could not get through.

The 'Campaign for Eastern New Guinea' was followed by the 'Campaign for the Finisterre Mountain Range', which secured the Huon peninsula.