The battle of Cape Gloucester (26 December 1943-April 1944) was the main American attack during Operation Dexterity, the invasion of western New Britain, and was carried out in order to secure control of the Dampier and Vitiaz Straits, between New Britain and New Ireland.
The western end of New Britain was important for two reasons. First, it would allow the Allies to tighten their grip on Rabaul, the powerful Japanese base at the northern tip of the island. Second, it would give the Allies control of the Dampier Strait, which ran between New Britain and the smaller island of Umboi (or Rooke). The allied campaign on the Huon Peninsula had given them control of the Vitiaz Strait, between Umboi and New Guinea. Once both straits were in Allied hands they could be used by shipping heading further west along the coast of New Guinea, and eventually on the return to the Philippines.
The Japanese had decided that an invasion of western New Britain was probably going to be the next Allied move. In September General Iwao Matsuda had been sent from Rabaul to the western end of the island. In October the 17th Division began to reach Rabaul from China, and most of it was then ordered west to join Matsuda. When the Americans landed the Japanese had the 65th Brigade, the 4th Shipping Group and part of the 17th Division at Cape Gloucester, around 10,000 men.
The attack was to be carried out by the US Marines, under General William Rupertus. The plan was for a two-pronged attack on either side of Cape Gloucester. The 2nd Battalion, 1st Marine Division, was to attack at Tauali, on the western side of the peninsula, and cut off the main road, isolating the Japanese defenders. Combat Team C, of the 7th Marines, was to land in Borgen Bay, to the east of the peninsula and establish a beachhead. They would then be joined by Combat Team B, made up of the rest of the 1st Marines. Combat Team B would advance inland and capture the Japanese airfield on the cape.
Eleven days before the Cape Gloucester landings another force landed at Arawe on the southern coast of western New Britain. This was a diversionary attack, intended to attract Japanese attention away from Cape Gloucester. The Japanese did commit some troops to this battle, but the slow speed of movement on the island meant that it didn't have much impact on the fighting at Cape Gloucester.
The western landings went without a hitch. When the Marines landed on the morning of 26 December they found the Japanese defences around Tauali abandoned and met with no resistance. By the end of the day they had blocked the road along the west coast of the cape.
In the east there were more problems, but these were mostly caused by the terrain. Pre-invasion reconnaissance had suggested that there was a damp flat area behind the beaches, but this turned out to be a deep swamp. The first US fatality of the invasion was actually caused by a falling tree in the swamp, undermined by US artillery fire. Despite the difficult terrain the 7th Marines managed to get across the swamp without running into heavy resistance and established a position on dryer ground some 900 yards inland.
The 1st Marines then passed through them as planned and began to advance towards the airfield. They ran into the first Japanese defences, a network of four bunkers, and were held up for some time. Eventually an Amtrak that had been called inland managed to destroy one bunker, and this gap in the network allowed the Marines to finish off the rest.
On 27 December the Marines advanced three miles along the coastal road towards the airfield.
On the night of 27-28 December the Japanese launched a fierce counterattack against the original landing point. The attack failed and cost the Japanese at least 200 dead.
At noon on 28 December the Marines ran into a stronger defensive position, this time of twelve bunkers, with over 250 men. By now the Marines had landed their tanks, and a combination of 75mm HE shells and infantry quickly eliminated this position. The Americans lost 9 dead and 36 wounded, the Japanese at least 266 dead. The area was given the name Hell's Point by the Marines, but the opposition was overcome far more quickly than this would suggest.
On 29 December the Marines reached the eastern end of the airfield and emerged from the jungle. Expecting to meet fierce resistance they formed up for a formal assault, with the tanks supported by infantry groups and artillery, but the Japanese failed to appear in any numbers and the airfield was taken very quickly.
The Japanese reappeared on 30 December. They had taken shelter to the south of the airfield during the American attack and now carried out a banzai attack. As was so often the case this was a total failure, and the survivors fled into the mountains in the centre of the peninsula.
The newly captured airfield took quite a lot of effort to bring back into use. US attacks had left 27 damaged Japanese aircraft scattered across the runways, the ground turned to mud and the area now came under Japanese attack. Even so the airfield was ready for its first Allied aircraft by mid-February.
This didn’t end the fighting around Cape Gloucester. The Japanese still had a large number of troops to the south of Borgen Bay, and were potentially within artillery range of the airfield. The terrain in this area was typical of that encountered in much of the New Guinea campaign, with a series of steep sided jungle covered ridges leading up to Hill 660, the key position in the area. The Japanese had built bunkers and emplacements on most of these ridges and would have to be evicted from each in turn. Very few weapons were effective in this terrain. The tanks that had been so effective on the road to the airfield couldn't cope. Bazookas and flame throwers lost much of their impact in the wet while the thick foliage meant that mortars, grenades and artillery were ineffective against the bunkers. The answer was to get up really close and use explosives to destroy the bunkers.
It took the Marines the first half of January to advance the two miles between the landing positions and Hill 660. On 12 January the hill was the target of a powerful air and artillery bombardment, and on 13 January the 3rd Battalion, 7th Marines (Colonel Buse), made their first attack on the hill. The main attack was made from the north-west, while a second detachment, with an armoured bulldozer, was sent around to the south to cut off the defenders. The main attack failed, but the bulldozer party, under Captain Joseph Buckley, did manage to get into place.
The Marines attacked again on 14 January, and this time, with support from 60mm mortars, they managed to reach the summit of the hill. The Japanese were forced to retreat into the surrounding jungle, while many of them ran into Buckley's roadblock. A few days of minor skirmishes followed before soon after dawn on 16 January the Japanese made one final banzai attack on the hill. They managed to reach the summit in some places, but were eventually repulsed with heavy losses. The battle for Hill 660 cost the Marines 50 dead and wounded, while the Japanese lost 200 dead.
The capture of Hill 660 secured the Cape Gloucester area. The Marines then slowly advanced east, to give themselves a strong defensive perimeter. Their final target was the Willaumez Peninsula and the airfield at Talasea. On 6 March they carried out a new amphibious attack at Talasea, and after a few days fighting had taken control of the area. That marked the effective end of the American campaign on New Britain, and at the end of April the Marines were relieved by the Army's 40th Division.