The 'Battle of Cape Gloucester' was fought between Allied and Japanese forces on the island of New Britain, off the eastern coast of New Guinea (26 December 1943/16 January 1944).
The battle was the heart of the 'Backhander' undertaking within the wider 'Cartwheel; strategic operation, the main Allied strategy in the South-West Pacific Area and Pacific Ocean Areas during 1943/44. It was the second landing by Major General William H. Rupertus’s US 1t Marine Division. The objective of the operation was to capture the two Japanese airfields near Cape Gloucester that were defended by elements of Lieutenant General Yasushi Sakai’s Japanese 17th Division of General Hitashi Imamura’s 8th Area Army.
The main landing was made on 26 December 1943, when US Marines came ashore on each side of the peninsula. The western landing force served as a diversion and cut the coastal road near Tauali to limit the Japanese forces' freedom of movement, while the main force, landing on the peninsula’s eastern side, advanced to the north toward the airfields. The US advance initially encountered only slight resistance, but was then slowed by the swampy terrain, which channeled the US troops onto a narrow coastal trail. A Japanese counterattack briefly slowed the advance, but by the end of December, the airfields had been captured and consolidated by the US Marines. Fighting continued into the early part of January 1944 as the US troops extended their perimeter to the south from the airfields toward Borgen Bay. Japanese organised resistance came to an end on 16 January 1944 when US troops captured Hill 660, but mopping-up operations in the area continued into April 1944, when the US Marines were relieved by US Army forces.
Cape Gloucester is a headland on the northern peninsula at the western end of New Britain island, which lies to the north-east of the New Guinea mainland. It is roughly opposite to the Huon peninsula, from which it is separated by Rooke island, which separated from New Guinea and New Britain by Vitiaz Strait and Dampier Strait respectively. At the time of the battle New Britain was part of the Territory of New Guinea. Cape Gloucester lies 230 miles (370 km) to the west-south-west of Rabaul, and 245 miles (394 km) to the north east of Port Moresby. The peninsula on which Cape Gloucester sits has an approximately semi-circular coast, extending from Lagoon Point in the west to Borgen Bay in the east. At the base of the peninsula is Mt Talawe, a 6,600-ft (2000-m) extinct volcano, which runs laterally east to west. To the south-west of Talawe, a semi-active volcano, Mt Langila, rises to 3,800 ft (1200 m), while farther to the south, a second extinct volcano, Mt Tangi, rises to 5,600 ft (1,700 m). The area is densely covered by thick rain forest, sharp kunai grass and deep mangrove swamps. In 1943, there were only a few beaches suitable for landing operations and along the coast there were no roads suitable for quick movement by troops and vehicles. The temperature ranges from 22° to 32° C (72° to 90° F), and the humidity is universally high. The rainfall is heavy, especially during the north-western monsoon season lasting to February. Air operations in this period could be mounted from Finschhafen on New Guinea, but after February the climate there was expected to restrict air operations, which would then have to be undertaken from Cape Gloucester. The climate dictated the timetable for 'Backhander'. In 1943, an Allied intelligence survey of the area estimated the population of the Cape Gloucester area at around 3,000 persons. There were numerous villages spread across four main areas: on the western coast near Kalingi; on the western bank of the Itini river in the south; inland from Sag Sag and toward Tauali on the western coast; and to the east of Mt Tangi around Niapaua, Agulupella and Relmen. Before the Japanese 'R' seizure of New Britain in 1942, there had been two European missions around Cape Gloucester: a Roman Catholic mission at Kalingi and an Anglican mission at Sag Sag.
Before World War II, a landing ground had been established on the relatively flat ground at the apex of the peninsula. Following the Japanese seizure of New Britain, the landing ground had been developed into two airstrips, of which the larger has a runway 3,900 ft (1190 m) long. The area was assessed by Allied intelligence as largely unsuitable for major development, with reefs to the south, west and north hampering the movement of large vessels, and a lack of protected anchorages suitable for such vessels. The few areas suitable for such vessels were open to the sea and were not considered perennial as they are affected by the changing seasons. Even so, small craft could operate along the coast, and Borgen Bay had been developed by the Japanese into a staging area for barge operations between the New Guinea mainland and the main Japanese base area in the Rabaul region on the eastern end of New Britain island.
By a time late in 1943, the fighting in New Guinea had turned in favour of the Allies after a period of hard fighting. The Japanese drive on Port Moresby during 1942 and early 1943 had been defeated during the 'Battle of the Coral Sea' and the Kokoda Track campaign. The Japanese beach-head at Buna and Gona had been effectively destroyed, albeit with many casualties. The Japanese had been forced to abandon their efforts on Guadalcanal and the Allies had secured the Salamaua region of New Guinea. The Allies then seized the initiative and implemented 'Cartwheel', which comprised a series of operations aimed at the reduction of the Japanese base at Rabaul and the severing of the Japanese lines of communication in the South-West Pacific Area, as the Allies advanced towards the Philippine islands group, which the Allies planned to retake in 1944/45. Australian forces had secured Lae by 16 September 1943 and operations to capture the Huon peninsula had begun in earnest shortly after this, to secure Finschhafen before a drive on Saidor. A secondary effort pushed inland from Lae through the Markham and Ramu river valleys, with the two drives eventually aiming towards Madang. As the Allied forces began to make headway on the Huon peninsula, Allied attention turned to securing the seaward flank on the other side of the Vitiaz and Dampier Straits.
On 22 September, General Douglas MacArthur, commander-in-chief of the South-West Pacific Area, issued orders for the 'Dexterity' invasion of New Britain. This undertaking was conceived on the basis of several phases, with the broad Allied scheme being to secure all of New Britain to the west of the line between Gasmata and Talasea on the southern and northern coasts respectively. Within this scheme, 'Backhander' was a landing around Cape Gloucester aimed at the capture, and expansion of, two Japanese airfields. This was to contribute to the increased isolation and harassment of the major Japanese base at Rabaul, which was subjected to heavy bombing in October and November, as part of continuing efforts to neutralise the large Japanese base area and garrison there without the need for any direct assault. A secondary objective was to ensure free Allied passage through the two straits separating New Britain and New Guinea. Among Allied commanders there was some debate about the necessity of invading New Britain. Lieutenant General George C. Kenney, the US air commander, believed that the landing at Cape Gloucester was unnecessary, and that it would take too long for the airfields to be developed and that the pace of Allied advance would ultimately outstrip their utility. Nevertheless, army and naval commanders felt it was necessary to secure the convoy routes through the Vitiaz Strait in order to support operations farther to the west on New Guinea’s north-western coast.
The landing at Gasmata was later cancelled and replaced with the 'Director' diversionary landing around Arawe for the possible establishment of a PT-boat base. Believing that the Allies could not bypass Rabaul as they attempted to advance towards the Japanese inner defensive perimeter and would therefore seek to capture Rabaul as quickly as possible, the Japanese sought to maintain a sizeable force for the defense of Rabaul, thus reducing the forces available for the defence of western New Britain.
Responsibility for the seizure of western New Britain was given to Lieutenant General Walter C. Krueger’s 'Alamo' Force. For 'Backhander', US planners assigned Rupertus’s 1st Marine Division, which had previously fought on Guadalcanal in the 'Watchtower' campaign. 'Backhander' would be the 1st Marine Division’s second landing of the war. Initial planning had envisaged an airborne landing by the 503rd Parachute Infantry near the airfields in conjunction with a seaborne landing on each side of the cape, with two battalions of the 7th Marine Regiment advancing on the airfields from the beaches to the north of Borgen Bay, and another marine regiment blocking ingress and egress routes along the opposite coast around Tauali. The airborne landing was later removed from the plan, however, as a result of concerns about overcrowding on staging airfields and the possibility of weather-caused delays. To compensate for this, the size of the seaborne assault forces was increased. The main force assigned to the assault was drawn from Colonel Julian N. Frisbie’s 7th Marine Regiment reinforced by Colonel William J. Whaling’s 1st Marine Regiment. In addition, Colonel John T. Selden’s 5th Marine Regiment constituted the reserve. Artillery was provided by Colonel Robert H. Pepper’s (later Colonel William H. Harrison’s) 11th Marine Regiment. These units were organised into three combat teams, designated 'A' to 'C': the 5th Marines formed Combat Team A, the 1st Marines Combat Team B and the 7th Marines Combat Team C.
In the middle of 1943, elements of the 1st Marine Division had still been in Australia, to which they had been withdrawn following the fighting on Guadalcanal. Around this time, preliminary landing rehearsals had been conducted around Port Phillip Bay, near Melbourne in the southern Australian state of Victoria, before the division’s movement to the forward assembly areas in New Guinea during August and September. Most of the Allied amphibious assets were tied up with operations around the Huon peninsula, however, and this meant that only limited rehearsals could take place before November. The combat teams moved into three staging locations (Milne Bay, Cape Sudest and Goodenough island), after which more rehearsal landings were undertaken around the Taupota Bay area, before the combat teams were concentrated at Cape Sudest in the Oro Bay area, to the south-east of Buna, in December.
The US troops were opposed by elements of Sakai’s 17th Division, which had served in China before arriving on New Britain in October and November 1943. These troops were known as the 'Matsuda' Force after their commander, Major General Iwao Matsuda, and comprised the 65th Brigade with the 53rd Regiment and 141st Regiment together with elements of the 4th Shipping Group. These troops were supported by field and anti-aircraft artillery, and a variety of supporting elements including engineers and signallers. Just before the battle, there were 3,883 troops in the vicinity of Cape Gloucester. Matsuda’s headquarters had been located at Kalingi, along the coastal trail to the north-west of Mt Talawe and within 5 miles (8 km) of the Cape Gloucester airfields, but after the Allied pre-landing bombardment, had been moved to Egaroppu, closer to Borgen Bay. The headquarters at Kalingi was taken over by the Colonel Koki Sumiya, commander of the 53rd Regiment, which defended the airfields primarily with the 1/53rd Regiment supported by elements of two artillery battalions, one heavy weapons company and one battalion of anti-aircraft guns. The 2/53rd Regiment was in reserve around Nakarop, while Colonel Kenshiro Katayama’s 141st Regiment was located well to the south around Cape Bushing. At the time of the fighting around Cape Gloucester, the capability of these troops had been seriously degraded by disease and lack of supplies, the latter resulting from the interdiction of the Japanese coastal supply barge traffic. Air support was available from the naval aircraft of Vice Admiral Jinichi Kusaka’s 11th Air Fleet and army aircraft of Lieutenant General Giichi Itahara’s 6th Air Division.
The 'Backhander' landing on Cape Gloucester was scheduled for 26 December. The planners ordered that a supply stockpile, sufficient for one month of combat operations, be established around Oro Bay, and this was in place by 16 December and would be shuttled to Cape Gloucester by landing craft as and when required. The day before the landing, supporting operations began as the US Army’s 112th Cavalry Regiment made the 'Director' landing at Arawe on the west central part of the island’s southern coast to block the route of Japanese reinforcements and supplies from east to west and as a diversion from the Cape Gloucester landings. The operation around Arawe succeeded in diverting about 1,000 Japanese troops from Cape Gloucester.
Over a period of several months before the 'Backhander' landing, the area around the airfields and the coastal plain between Cape Gloucester and Natamo, to the south of Borgen Bay, had been bombed by Allied aircraft, mainly of K enney’s US 5th Army Air Force. Japanese defensive positions were destroyed and the airfields around Cape Gloucester were put out of action from November. A total of 1,845 sorties were flown by US aircraft against targets around Cape Gloucester, with the expenditure of almost three million rounds of ammunition and 3,865 tons of bombs. Diversionary air raids were also made by warplanes of Major General Ralph J. Mitchell’s Air Solomons command in the days before the assault, and these focused on the Japanese airfields around Rabaul, while carrierborne aircraft bombed Kavieng on New Ireland island. Raids were also launched against Madang and Wewak. The Allies meanwhile undertook extensive aerial reconnaissance of the area, while ground teams of marines, Alamo Scouts and coastwatchers were landed at various locations except Borgen Bay over three separate occasions from PT-boats between September and December 1943.
The Japanese defensive planning was concentrated on holding the airfield area. Bunkers, trenches and fortified positions were built along the coast to the east and west, the strongest position being established to the south-east, to defend against an approach through the flat grasslands. A complex was also established at the foot of Mt Talawe, affording a commanding view of the airfields, which were held by an infantry battalion supported by service troops and several pieces of artillery. To the east of the peninsula, the beaches around Silimati Point, which were hemmed by heavy swamps, were left largely unfortified, the Japanese defensive scheme being based on holding several high features, Target Hill and Hill 660, and maintaining control of lateral tracks so that forces could be moved rapidly in response to an attack.
The Allied plan called for a two-pronged landing at several beaches to the east and west of the peninsula, followed by an advance to the north in the direction of the airfields at Cape Gloucester. Final rehearsals were undertaken on 21 December, after which the troops embarked on their vessels early on 25 December at Oro Bay and Cape Cretin near Finschhafen. The convoy, designated Task Force 76 under the command of Rear Admiral Daniel E. Barbey, comprised nine older destroyers adapted as high-speed transports, 19 infantry landing craft, 33 tank landing ships, 12 mechanised landing craft and 12 tank landing craft, escorted by 12 destroyers as well as the task force flagship (the destroyer Conyngham), three minesweepers and two rocket-carrying DUKW amphibious trucks carried aboard the LCMs. These two amphibians were to support the western landings, while two LCIs had been similarly modified to support the eastern landing.
The troops were carried aboard the APD destroyer conversions, while the LSTs carried the heavy vehicles including bulldozers, tanks and trucks. A 20-day supply of rations was detailed for the assault troops, while the follow-on troops were to land with 30 days of supply. Both groups were to carry three units of ammunition resupply, while five days were needed for anti-aircraft weapons. Nevertheless, space was at a premium and in some instances, could not be met. In order to speed the unloading process and reduce congestion on the eastern beaches, a mobile loading scheme was devised with the supplies pre-loaded directly on 500 2.5-ton trucks. These vehicles would arrive on the beaches with the morning’s troop-landing first echelon and would be able to drive straight off the LSTs and unload their cargo at several dumps ashore before re-embarking on LSTs assigned to the second echelon, which was to land in the afternoon of the first day with the follow-on troops. Medical teams, including doctors and corpsmen, were assigned to each transport and some LSTs, and these personnel would form part of an evacuation chain that would see casualties transported back to Cape Sudest, where an 88-bed floating hospital was established aboard an LST to serve as a casualty-receiving station before casualties were moved to base hospitals ashore.
The assault force was escorted by US and Australian cruisers and destroyers of Task Force 74, under the command of the British Rear Admiral V. A. C. Crutchley. Maintaining a speed of 12 kt, the convoy proceeded through the Vitiaz Strait toward Cape Gloucester, passing between Rooke and Sakar islands. As the Allied ships made their way toward their objective, Allied patrol boats operated in the northern and western approaches, the Dampier Strait and the southern coast of New Britain. While heading toward their objective, the convoy was spotted by a Japanese reconnaissance aeroplane as well as an observer on Cape Ward Hunt. As a result, the progress of the Allied ships was reported to Rabaul where, however, Kusaka incorrectly assessed that the convoy was bound for Arawe as a reinforcement, and subsequently ordered a heavy air attack there instead of around Cape Gloucester with 63 Mitsubishi A6M Reisen 'Zero' single-engined fighters and 25 bombers from Rabaul.
The 'Backhander' operation began just after dawn on 26 December with a naval bombardment of the Japanese positions on the cape and then air attacks by aircraft of the USAAF and RAAF. For close air support, a total of 14 squadrons (nine of bombers and five of attack aircraft) of Brigadier General Frederick A. Smith’s 1st Air Task Force was provided. In addition, several fighter squadrons flew combat air patrols to negate the threat from Japanese aircraft: one squadron covered the convoy’s approaching, three covered landing beaches, and another covered the seaborne elements that would withdraw in the afternoon. These attacks and an aerial smokescreen were followed by the landing of the 1st Marine Division, at Beaches Yellow 1 and 2 to the east near Silimati Point and Borgen Bay, about 5 miles (8 km) to the south-east of the airfield, and a diversion at Beach Green to the west at Tauali, about 6.5 miles (10.5 km) from Cape Gloucester. The main assault came at Silimati Point, only one battalion landing in the west. After being transported aboard the APDs from Cape Sudest, the force came ashore in landing craft of various types including, LSTs and LCIs.
The Beach Green diversionary western landing at Tauali, on the Dampier Strait side of the peninsula, was assigned to Landing Team 21, comprising the 2/1st Marines together with a battery of artillery of the 11th Marines. Escorted by two destroyers and two patrol boats, the force was carried by 31 landing craft of various types (five LCIs, 12 LCTs and 14 LCMs), and carried with it 20 days of rations and six units of artillery ammunition. After departing Oro Bay on Papua’s south-western coast the main convoy, this force separated around Finschhafen and proceeded on its own through the Dampier Strait. After the preliminary naval and air bombardment at about 07:30, the force came ashore to discover that the Japanese defences around Beach Green had been abandoned. Landing Team 21 therefore experienced no opposition coming ashore, preceded by heavy preparatory fires including rockets fired from several amphibious vehicles. The beach-head had been established by 08.35 and all first-day objectives had been secured by 10.00. As a result of interference from the surrounding area, the marines were unable to raise their divisional headquarters, and were instead had to relay messages through the headquarters of the 6th Army ('Alamo' Force). By the fall of night, the marines had secured a perimeter and cut the coast road with a road block. This prevented the Japanese from using the road to reinforce their positions round the airfields, but a secondary route, to the east of Mt Talawe, remained open to the Japanese as it had not been detected by US intelligence.
Shortly after the western landing, the Japanese despatched two companies of the 53rd Regiment to respond. In the days that followed, the marines clashed with small groups of Japanese, and Japanese artillery and mortars fired on the US perimeter from Dorf Point. Patrol clashes increased in number until the early morning of 30 December when the two companies of the 53rd Regiment attacked the marines around 'Coffin Corner', exploiting the concealment of a heavy storm and darkness to launch a concentrated assault along a narrow avenue of approach between two defended ridges. Supported by machine gun, mortar and artillery fire, the Japanese launched an assault that was repulsed only after a five-hour firefight. The Japanese casualties amounted to 89 men killed and five taken prisoner, against marine losses of six men killed and 17 wounded. After this, there were no further assaults on the western perimeter. Artillery fell on the position on 31 December, but was met by counter-battery fire from the 11th Marines, who had a hard task getting their guns into action because of the terrain. Although the Japanese sought mainly to avoid contact as most of them were withdrawn to support the fighting on the eastern coast, patrol actions continued throughout the early part of January 1944, when contact was established around Dorf Point with a company-sized patrol of the 5th Marines that had set out overland from the eastern beach-head. The wounded and heavy equipment were then evacuated on 11 January, having earlier been hampered by poor weather, and Landing Team 21 then collapsed its position, marching east toward the airfields, and on 13 January linked with the main body of US troops, which had captured the airfields late in December.
The remainder of Task Force 76, comprising nine APDs, 14 LCIs and 33 LSTs, was allocated to the eastern zone (Beaches Yellow 1 and 2), and carried Combat Team A from Milne Bay and Combat Team B from Finschhafen. The 7th Marines were to go ashore first with the task of securing the beach-head, while the 1st Marines (less the battalion assigned to the diversionary landing around Tauali) followed after the initial assault and passed through their lines to begin the advance to the north in the direction of the airfield. The 5th Marines remained embarked as the floating commander’s reserve for release on Krueger’s orders.
As the ships of the task force moved into position, the approaches to the beach were marked and cleared during the dark hours, and at 06.00, 105 minutes before the scheduled landing time, a heavy naval bombardment began as the cruisers engaged targets round the airfields and round the beaches and toward Target Hill. As H-hour approached, the escorting destroyers also joined in the bombardment, followed by a carefully co-ordinated bombing raid by five squadrons of Consolidated B-24 Liberator four-engined heavy bombers and one squadron of North American B-25 Mitchell twin-engined medium bombers, which attacking Target Hill. The first wave of assault troops disembarked from the APDs and were loaded into 12 LCVPs: six were bound for Beach Yellow 1 and the other six for Beach Yellow 2. While the APDs withdrew, the LCVPs began their run to the shore. After the B-25 bombers had made a final strafing run over the beach, two rocket-equipped LCIs stationed to the flanks fired onto the beach defences.
Drifting smoke from the bombing of Target Hill obscured the beaches and the approaches, and briefly hampered the landing, with some troops coming ashore in the wrong place. Nevertheless, the first wave made landfall around Beach Yellow 1 one minute after H-hour, followed two minutes later by the first arrivals on Beach Yellow 2. There was no opposition in the vicinity of the two beaches, but the small group of the 3/7th Marines that landed 300 yards (270 m) to the north-west of Beach Yellow 1 by mistake ad pushed through the thick jungle to locate the coastal trail came under fire from machine guns firing at maximum range from a number of bunkers. Throughout the morning, follow-up troops from the remainder of the 1st Marines came ashore and pushed through the 7th Marines to begin the northward advance toward the airfields. The landing area to the north of Borgen Bay, was surrounded mostly by swamp, with only a small narrow beach along which the marines and their supporting Sherman medium tanks of the 1st Tank Battalion could advance toward the airfields. This slowed the inland advance and resulted in heavy congestion on the beaches, which complicated unloading operations.
After initially being diverted toward Arawe in the morning, Japanese aircraft, after refueling and rearming at Rabaul, began to attack the Allied ships off the landing beaches at about 14.30, resulting in the loss of the destroyer Brownson with more than 100 men of her crew, and casualties aboard the destroyers Shaw and Mugford. Nevertheless, around 13,000 troops and about 7,600 tons of equipment were landed during the first day of the operation on either side of the cape, and the attacking Japanese aircraft suffered losses to US fighters and shipborne anti-aircraft fire. Opposition in the main landing area was limited initially to rear-area troops who were overrun, but a hasty counterattack by Major Shichi Takabe’s 2/53rd Regiment, which had marched from Nakarop, lasted through the afternoon and evening of the first day, falling mainly against Lieutenant Colonel Odell M. Conoley’s 3/7th Marines. By the end of the day, the 7th Marines held the beach-head, while the 11th Marines had landed their artillery, and the 1st Marines had begun a slow advance to the north, forced into a long column along the narrow trail.
On the following day the marines advanced westward, pushing 3 miles (4.8 km) toward their objective, before reaching a Japanese blocking position, which was identified by the marines as 'Hell’s Point', on the eastern side of the airfields. This position was well concealed, and equipped with anti-tank and 75-mm (2.95-in) field guns. Teams from the 19th Naval Construction Battalion (designated as the 3/17th Marines) worked to improve the routes along which the US forces were advancing as large quantities of supplies were landed. Amphibian landing vehicles were used to ferry ammunition forward, but the volume of traffic, coupled with the heavy rain, churned up the narrow coastal road to the extent that the movement of combat supplies forward from the Beaches Yellow, as well as evacuation of the wounded back from the engagement areas, proved difficult. On 28 December, a secondary landing beach was established as Beach Blue about 4 miles (6.4 km) closer to the fighting in an effort to reduce the distance supplies had to travel once landed. At the same time, the blocking position was attacked and US armour was brought up. Nine marines were killed and 36 were wounded, while Japanese losses amounted to at least 266 men killed.
The 5th Marines, in reserve for the initial landing, were landed on 29 December. There was some confusion during the landing as a result of a last-minute change in orders for the regiment to land on Beach Blue rather than Beaches Yellow 1 and 2. As a result, the regiment came ashore in both locations, with those who arrived on the Beaches Yellow marching to Beach Blue or being moved by truck. After establishing themselves ashore, the 5th Marines carried out a flanking move to the south-west, while the 1st Marines continued to advance along the coast. By the end of the day, the marines had broken through the Japanese defences and were in control of most of the airfield. Japanese air attacks ended on 29 December with the arrival of bad weather. This was followed by much US air activity around Rabaul, which prevented further air attacks on Cape Gloucester. During the last days of December, the marines overran the airfield area and expanded their perimeter, incorporating 'Razorback Ridge', a key feature about 1,500 yards (1370 m) to the south of No. 2 Strip running north to south. Early in January, Company E of the 2/5th Marines linked with the western lodgement around Dorf Point on the western coast.
In the weeks that followed the capture of the airfield, US troops pushed to the south toward Borgen Bay so as to extend the perimeter beyond Japanese artillery range. In this time, further actions were fought by the 5th and 7th Marines against the remnants of the 53rd Regiment and 141st Regiment, which had undertaken a march north across difficult terrain from Cape Bushing, following the initial landings. On 2 January, there was a sharp engagement around 'Suicide Creek', when the advancing marines encountered a heavily entrenched defending force of the 53rd Regiment. Held up by strong defences well concealed in the dense jungle, the marines were halted and dug in temporarily around 'Suicide Creek'. On the next day, a reinforced company of the 141st Regiment launched an unsuccessful counterattack on the US troops around Target Hill. This was followed by renewed fighting around 'Suicide Creek' as the Japanese put up a stubborn defence, which was eventually overcome with the assistance of tanks and artillery on 4 January.
After reorganising on 5 January, US troops secured Aogiri Ridge and Hill 150 on 6 January. This was followed by an action toward the high ground around Hill 660. Slowed by bad weather, rugged terrain and Japanese resistance, the marines' progress around Hill 660 was slow, and the position was finally secured on 16 January after three days of fighting in which 50 marines and more than 200 Japanese were killed. The capture of this position represented the end of Japanese defensive operations in the Cape Gloucester and Borgen Bay areas. Following this, Matsuda withdrew with some 1,100 men, ceding the area to the Americans, who captured his command post intact.
The base engineer and his operations staff landed on 27 December 1943 and had completed a reconnaissance of the two Japanese airfields by 30 December. They found that they were 3 ft (0.91 m) deep in kunai grass and that the Japanese had attempted neither to construct proper drainage nor to regrade the runways. The Americans decided not to proceed with any work on No. 1 Airstrip and to concentrate their efforts on No. 2 Airstrip. The 1913th Engineer Aviation Battalion arrived on 2 January, followed by the 864th Engineer Aviation Battalion on 10 January and the 841st Engineer Aviation Battalion on 17 January. Work hours were limited by black-out restrictions imposed by the task force commander, which limited work to daylight hours until 8 January 1944, and by heavy and continuous rain from 27 December 1943 to 21 January 1944, averaging 10 in (254 mm) per week. Grading removed 3 to 6 ft (0.91 to 1.83 m) of material, mostly kunai humus, from two-thirds of the area. The subgrade was then stabilised with red volcanic ash that had to be hauled from the nearest source 8 miles (13 km) away. Marston Mat was then laid over the top, but this did not arrive until 25 January, resulting in further delay. By 31 January, 4,000 ft (1220 m) of runway was usable and by 18 March a 5,200-ft (1585-m) runway had been completed. Natural obstacles prevented the runway being lengthened to 6,000 ft (1830 m) as originally planned, but there were four 100 by 750-ft (30 by 229-m) alert areas, 80 hardstands, a control tower, taxiways, access roads and facilities for four squadrons.
A Beech C-45 twin-engined light transport aeroplane had landed on the runway at Cape Gloucester in January, followed by a Douglas C-47 Skytrain twin-engined medium transport aeroplane and Smith on 9 January, and estimated that the 8th Fighter Group could move into the new base as early as 15 January. This did not prove feasible, for the base had not been completed and was already at capacity with transport aircraft bringing in much-needed supplies. The 35th Fighter Squadron arrived on 13 February, followed by the 80th Fighter Squadron on 23 February. Heavy rains made mud ooze up through the holes in the steel-plank matting, making the runway slick. This did not bother the 35th Fighter Squadron, which flew nimble and rugged Curtiss P-40 Kittyhawk single-engine fighter-bombers, but the Lockheed P-38 Lightning twin-engined heavy fighters of the 80th Fighter Group found themselves overshooting the short runway. Major General Ennis C. Whitehead, commander of the 5th Army Air Force Advanced Echelon, decided to move the 8th Fighter Group to Nadzab and replace it with Australian Kittyhawk squadrons from Kiriwina. The RAAF’s No. 78 Wing began moving to Cape Gloucester on 11 March: No. 80 Squadron arrived on 14 March, followed by No. 78 Squadron on 16 March and No. 75 Squadron two days later. No. 78 Wing provided close air support for the 1st Marine Division, assisted the PT-boats offshore and provided vital air cover for convoys headed to the 'Brewer' campaign in the Admiralty islands group. Operations were maintained at a high tempo until 22 April, when No. 78 Wing was alerted to prepare for the 'Reckless' and 'Persecution' landings at Hollandia and Aitape.
To support air operations, 470,000 Imp gal (2100000 litres) of bulk petroleum storage was provided, along with a tanker berth with connections to the five storage tanks, and this became operational in May 1944. The 19th Naval Construction Battalion worked on a rock-filled pile and crib pier 130 ft (40 m) long and 540 ft (160 m) wide for 'Liberty' ships, but this had not been completed before the 19th Naval Construction Battalion left for the Russell islands group, along with the 1st Marine Division, in April 1944. Other works included 800,000 sq feet (74320 m²) of open storage, 120,000 sq feet (11150 m²) of covered warehouse storage and 5,400 cu ft (153 m³) of refrigerated storage; a 500-bed hospital was completed in May 1944 and a water supply system with a capacity of 25,000 Imp gal (110000 litres) per day was installed. Despite problems obtaining suitable road surface materials, 35 miles (56 km) of two-lane all-weather road were provided, surfaced with sand, clay, volcanic ash and beach gravel. Timber was obtained locally, and a sawmill operated by the 841st Engineer Aviation Battalion produced 1,000,000 board ft (2400 m³) of lumber.
The US casualties during operations to secure Cape Gloucester amounted to 310 men killed and 1,083 wounded, while those of the Japanese were greater than 2,000 men killed in the period between December 1943 and January 1944.
Plans to move the 13th Army Air Force units to Cape Gloucester were cancelled in August 1944, sand this is reflected in the assessment of several historians that 'Backhander' was of only limited strategic importance in achieving the Allied objectives of 'Cartwheel'. Even so, the airstrip played a vital role in supporting the 'Brewer' campaign in the Admiralty islands group from February 1944 and as an emergency landing field for aircraft damaged in raids on Kavieng and Rabaul. It remained in use until April 1945. In June, the base at Cape Gloucester became part of Base F at Finschhafen.
Elsewhere, US and Australian forces conducted the 'Landing on Long Island', 80 miles (130 km) to the north-west, where a radar station was established in December. 'Alamo' Force switched its attention to the 'Dexterity' landing at Saidor of 2 January 1944 as part of the next stage of operations in New Guinea. In the middle of January 1944, the commander of the 17th Division, Sakai, sought permission to withdraw his formation from western New Britain. On 16 February, US patrols from Cape Gloucester and Arawe linked around Gilnit. A company of the 1st Marines landed on Rooke island on 12 February aboard six LCMs to ensure that it was clear of Japanese troops. After coming shore unopposed, the marines sent out patrols to reconnoitre the island and, after finding it abandoned, returned to Cape Gloucester on 20 February. From 23 February, the Japanese sought to disengage from the Americans in western New Britain and move towards the Talasea area. Marine patrols kept up the pressure, with several minor engagements fought in the centre of the island and along its northern coast.
Mopping-up operations around Cape Gloucester continued throughout the early part of 1944, although by February the situation had stabilised sufficiently for US planners to begin preparations to expand the lodgement farther to the east. Early in March 1944, the Americans launched an operation to capture Talasea on New Britain’s northern coast while following a general Japanese withdrawal toward Cape Hoskins and Rabaul. The 1st Marine Division was relieved around Cape Gloucester on 23 April and replaced by a US Army formation, Major General Rapp Brush’s 40th Division, which arrived from Guadalcanal. A lull on New Britain followed as the US forces limited their operations largely to the western end of the island, having decided to bypass Rabaul, while the Japanese remained close to Rabaul at the opposite end of the island. Responsibility for operations on New Britain was later transferred from the US to the Australian forces. In November 1944, they conducted the Landing at Jacquinot Bay for a limited offensive with the 'Battle of Wide Bay-Open Bay' securing the bays, to confine the larger Japanese force to the Gazelle peninsula, where they remained until the end of the war.