This was an Australian special forces operation by an eight-man part of the 'Z' Special Unit to investigate the Japanese defences on Mushu island, capture a Japanese officer for interrogation, and establish the location of two naval guns which covered the approaches to Wewak harbour on the north coast of North-East New Guinea (11 April 1945).
In 1941 Wewak had a good but almost completely undeveloped harbour. The village is located on a narrow coastal plain, with the Toricelli mountain range just behind the plain, which is crossed by numerous rivers and streams all readily liable flash flooding. The Old German Road followed the coastline but was little more than a trail. Japanese forces landed at Wewak on 1 January 1943 and then constructed a sizeable air base complex. By March 1943, most of Lieutenant General Heisuke Abe’s 41st Division had joined the garrison, its first elements having arrived on 12 February of the same year to reinforce Lieutenant General Hatazo Adachi’s 18th Army.
Between 16 and August 1943, bombers of Major General George C. Kenney’s US 5th AAF destroyed Wewak after a clever deception had drawn the attention of the Japanese away from a new fighter strip at Tsili Tsili. Kenney had ordered the construction of a large dummy airstrip at Bena Bena, a few miles from Tsili Tsili, and the Japanese did not discover the deception until 14 August, and by that date the Americans had assembled a large fighter force at Tsili Tsili.
By 10 August the Japanese had massed more than 250 aircraft at the Wewak airfield complex for an aerial counter-offensive, and these aircraft began to attack Tsili Tsili almost as soon as it was discovered. However, on 17 August, as the Japanese were preparing to launch a major attack on the new Allied airfield, a force of 48 heavy bombers, 31 North American B-25 Mitchell attack bombers and 85 Lockhgeed P-38 Lightning fighters from Tsili Tsili surprised the Japanese and destroyed 70 aircraft on the ground. A second attack on the following day destroyed many more Japanese aircraft. These operations broke the back of Japanese air power in central New Guinea.
Its rugged terrain made Wewak an unappealing target for direct assault, as did the large number of Japanese troops holding it. General Douglas MacArthur, heading the South-West Pacific Area command, therefore decided to bypass the area and strike farther to the west at Aitape and Hollandia ('Persecution' and 'Reckless') in April 1944.
Major General Jack E. S. Stevens’s Australian 6th Division advanced to the east in the direction of Wewak early in 1945, and this proved to be a controversial action in light of the fact that the isolated Japanese forces at Wewak now struggling just to feed themselves. Wewak itself fell on 11 May 1945, forcing the remnants of the 18th Army into the wilderness of the New Guinea interior, where most starved before Japan’s surrener in August 1945.
Undertaken in support of the Australian offensive toward Wewak, 'Copper' (ii) was one of the last 'Z' Special Unit operations in New Guinea. The unit’s task was to paddle ashore and reconnoitre Mushu island in order to determine the strength and disposition of the Japanese defences, and also to validate reports that two 140-mm (5.5-in) long-range naval guns were still there. Intelligence suggested that these weapons were back in service and could prove dangerous during the forthcoming assault on Wewak as they had sufficient range to fire into the proposed landing area, and while they could not prevent the planned Australian landing they might be able to inflict significant losses.
On the night of 11 April 1945, eight men of the 'Z' Special Unit were dropped near Mushu island by the patrol boat HDML-1321. The men were Special Lieutenant Alan Robert Gubbay, Lieutenant Thomas Joseph Barnes, Sergeant Malcolm Francis Max Weber, Lance Corporal Spencer Henry Walklate, Signaller Michael Scott Hagger, Signaller John Richard Chandler, Private Ronald Edward Eagleton and Sapper Edgar Thomas Dennis.
Caught by unexpected currents, the four Folboats were pushed to the south of their landing area and came ashore amid a surf break. All boats were swamped and some items of equipment were lost, but the men managed to get ashore and harbour until the morning. At the break of day the party began its reconnaissance of the island, soon encountering Japanese troops, who had found some of the Australians' equipment washed ashore further along the island. Thus alerted, the island became a hunting ground, with almost 1,000 Japanese searching for the part. Attempts to communicate by radio with the patrol boat failed as the party’s radio equipments had been swamped and their batteries ruined.
Of the eight men, the only survivor was Dennis, an experienced commando who had previously fought the Japanese in New Guinea in several significant engagements, escaped after fighting his way through Japanese patrols. Dennis swam the channel to Wewak, a distance of more than 1.85 miles (3 km) while being pursued by the Japanese, and then made his way through Japanese-held territory to meet an Australian patrol on 20 April. The information with which Dennis returned proved vital to keeping the guns out of action and in preventing the Japanese from using the island as a point from which to launch attacks against the Australian forces during the Wewak landings a month later.