Operation Deluge

'Deluge' was the Australian landing and subsequent campaign in the Aitape, Wewak and Sepik region of North-East New Guinea (November 1944/August 1945).

In 1941, Wewak was a good but almost completely undeveloped harbour on the north-eastern coast of New Guinea, and was the seat of the Sepik district of the Mandated Territory of New Guinea. Wewak is located on a narrow coastal plain, with the Toricelli mountain range just inland of it. This plain is crossed by many rivers and streams prone to flash flooding. The Old German Road followed the line of the coast but was little more than a trail.

Japanese forces landed here on 1 January 1943 and developed a sizeable air base complex. By March 1943, most of Lieutenant General Heisuke Abe’s 41st Division had joined the garrison.

The Aitape and Wewak campaign was one of the final campaigns to be fought in the Pacific theatre, or more specifically the South-West Pacific Area, of World War II. Major General Jack E. Stevens’s (from 26 July 1945 Major General Horace C. H. Robertson’s) 6th Division (Brigadier Roy King’s 16th Brigade, Brigadier Murray J. Moten’s 17th Brigade and Brigadier James E. G. Martin’s 19th Brigade), with air and naval support, fought Lieutenant General Hatazo Adachi’s 18th Army in North-East New Guinea from November 1944 to the end of the war in August 1945 in a programme that started with offensive patrols and small actions, and then from January 1945 began to develop into more major undertaking as the Australians pushed westward in the direction of Wewak against Japanese forces reinforced by units which had been isolated farther to the west and were now arriving to bolster Adachi’s hard-pressed army.

Considered a mopping-up operation by the Australians, and finally successful for them inasmuch as the last Japanese forces were cleared from the coastal areas and driven inland, to attempt survival amidst difficult jungle conditions, 'Deluge' was deemed highly problematical as casualties from combat and, still more so disease, were high. With Japan on the verge of defeat, such casualties later led to the questioning of the campaign’s strategic necessity.

In was during 1942 that the Japanese occupied the Aitape region toward the western end of North-East New Guinea as part of their general advance to the south and south-east. On 22 April 1944, however, US Army forces landed and recaptured the area in 'Persecution'. After this the Aitape area was developed as a major base from which support could be provided for the continuing Allied drive western along the north coast of New Guinea with the ultimate object of launching an amphibious assault to start the reconquest of the Philippine islands group.

As preparations for this drive got under way, it was decided that defence of the area would be passed to Australian forces in order to release US troops for service elsewhere. Early in October 1944, therefore, units of the Australian 6th Division, together with some support personnel of the 3rd Base Sub-Area, began to arrive at Aitape to relieve the US garrison. The first unit to arrive was the 2/6th Cavalry Commando Regiment, which began patrol operations almost immediately after arriving.

The Japanese troops in the Aitape area numbered about 30,000 to 35,000 men of the 18th Army. This formation had suffered heavily during the 'Postern' campaign for Salamaua and Lae in 1943/44, as well as its failed attack on the US garrison at Aitape in July 1944. As a result, the Australians believed that they faced three Japanese divisions (Lieutenant General Masutato Nakai’s 20th Division, Lieutenant General Goro Mano’s 41st Division and Lieutenant General Hidemitsu Nakano’s 51st Division) each of which had been reduced to little more than brigade strength. The Japanese lacked air and naval support, and many of their men were sick and short of food, for resupply efforts were limited to very occasional deliveries by aircraft or submarine.

By contrast, the Australians were better equipped and better fed in terms of quantity and quality, and also had the benefits of superior medical and other support services. They also had a moderate but tactically significant quantity of air support by No. 71 Wing of the RAAF, which included Nos 7, 8 and 100 Squadrons equipped with the Bristol Beaufort twin-engined torpedo bomber now used in the level bomber role, while air reconnaissance and close support were provided by CAC Boomerang and CAC Wirraway single-engined aircraft of No. 4 Squadron. A naval force, known as the Wewak Force, supported the landing at Dove Bay, and included the sloop Swan and the minesweepers Colac, Dubbo and Deloraine as well as the craft of the 1st New Guinea Motor Launch Flotilla all under the command of Commander William J. 'Bill' Dovers, captain of Swan.

The campaign was another notable example of the type of challenging jungle fighting in which casualties resulted from both battle and disease. The Japanese had occupied Aitape in December 1942 but this had then been recaptured by the US 'Persecution' landing on 22 April 1944 before being developed as a base area to support the continuing drive toward the Philippine islands group under the supervision of General Douglas MacArthur’s South-West Pacific Area. After its defeat during July along the Driniumor river, the 18th Army had pulled back from its forward positions, and there had followed a lull in which Adachi’s forces concentrated their efforts on mere survival, which involved major foraging operations into the Torricelli mountains and the Wewak area.

During this period there had been very little contact between the Japanese and US forces in the area, and the latter had remained largely on the defensive with limited patrolling forward of their position on the Driniumor river. As noted above, in order to free US troops for the Philippine operations, General Douglas MacArthur then passed the defence of the area to Australian forces.

Initially allocated the task of holding the port, airfield and base facilities at Aitape, the 2/6th Cavalry Commando Regiment was soon ordered by the offensively minded Stevens to move toward Wewak as the van of the Australian effort to destroy the remnants of the 18th Army. Patrols by the 2/6th Cavalry Commando Regiment preceded the main advance by the 6th Division.

The attack by the 6th Division, which had been converted to a jungle establishment (13,118 men, some 4,000 fewer than the standard division) started in November 1944 and moved on two axes: the 19th Brigade proceeded westward along the coast toward the Japanese base at Wewak, and the 2/6th Cavalry Commando Regiment, working with Australian New Guinea Administrative Unit detachments, advanced into the Torricelli mountains and moved on Maprik in the area which provided the Japanese with most of their supplies. With the advance under way, the 17th Brigade was made responsible for the building of a defensive position around the airfield and base facilities at Aitape, and the 16th Brigade was held in reserve. On 19 December the 19th Brigade crossed the Danmap river and headed to the east in an attempt to cut the main Japanese line of communication. There were a number of minor actions but no major engagements, and after four weeks the brigade had reached Wallum, about 45 miles (72 km) to the east of Aitape.

A week later, on 24 January 1945, the 16th Brigade relieved the 19th Brigade, and the 17th Brigade continued its westward progress through the Torricelli mountains.

Operations up to this time had been characterised by extended patrolling by small units, complemented at times with company-size attacks. Progress was slow, largely as a result of the difficulties associated with the movement of necessary supplies overland or by barge along the coast, and by the flash flooding of a number of the very many rivers the Australians had to cross.

After the Australians had occupied Dogreto Bay, their supply situation became easier. On 16 March the Australians occupied airfields at But and Dagua on the coast, but fighting inland of the two airfields continued for the next two weeks. In the Torricelli mountains the 17th Brigade continued its advance in the face of determined Japanese resistance, but by 23 April it had secured Maprik. The seizure of Maprik allowed the Australians to begin the construction of an airfield 8 miles (13 km) away at Hayfield, and the completion of the airfield on 14 May made its possible for reinforcements and supplies to be flown into the area.

Elsewhere the 19th Brigade had begun its assault on Wewak early in May with the gunfire support of four Australian warships (the light cruiser Hobart, the destroyers Arunta and Warramunga, and the sloop Swan) as well as the British light cruiser Newfoundland of Admiral Sir Bruce Fraser’s British Pacific Fleet, and the bombing of RAAF aircraft. On 11 May, 'Farida' Force made a landing at Dove Bay, thereby completing the Australian encirclement of Wewak and preventing the escape of its garrison. Wewak fell on the same day as the 19th Brigade occupied its airfield, but the fighting around the airfield continued until 15 May, when men of the 2/4th Battalion, supported by armour, attacked the Japanese positions overlooking the airstrip.

The Japanese left in the area now withdrew into the Prince Alexander mountains of Wewak. The 16th Brigade moved in pursuit with the object of pushing the Japanese toward the 17th Brigade, which was advancing to the east in the direction of Maprik. These operations continued until 11 August, by which time the 16th Brigade had reached Numoikum, about 14 miles (23 km) from Wewak, while the 17th Brigade had captured Kairivu, about 15 miles (24 km) from Wewak.

At this stage in the operation there arrived the news that the Japanese government had begun discussing the terms of a possible surrender, and offensive operations were brought to a halt.

By the end of the campaign, to which they had committed some 13,000 men, the Australians had lost 442 men killed and 1,141 wounded, together with another 16,203 incapacitated by any of the several tropical diseases endemic to the area. More than 9,000 Japanese had been killed and 269 taken prisoner from a strength of between 30,000 and 35,000 men.

After hostilities on New Guinea had come to an end, about 13,000 Japanese surrendered, and it is reckoned that some 14,000 had died of starvation and illness.

Even during the course of the campaign, its strategic necessity had been called into question as it became clear that the fighting would have little or indeed no impact upon the outcome of the war. In this regard it was argued that the Japanese forces in the area of Aitape and Wewak posed no strategic threat to the Allied advance toward the Japanese home islands, and that they could therefore be left in total isolation to 'wither on the vine' as they exhausted their already meagre supplies.

Even so, it must be admitted that at the time that the operation was planned there was no way Australian commanders could know when the war would come to an end, and that there were arguably sound operational and indeed political reasons for the implementation of the campaign.

By a time late in 1944 the Australian army had taken a secondary role in the war against the Japanese and there was a political and emotional need for Australia to demonstrate that it was sharing the burden in the Pacific theatre. As New Guinea was an Australian territory at the time, it was argued that there was a responsibility to clear the Japanese from this area. But as a result of manpower shortages in the Australian economy, the government had requested the army to reduce its size, while at the same time requiring it to maintain forces to undertake further operations against the Japanese into 1946. In order to do this, it has been argued that there was a requirement to clear bypassed Japanese forces in order to allow the Australian forces in these areas to be reduced.