Last week, Lloyd Austin became the first US defence secretary to visit Papua New Guinea, en route to the AUSMIN conclave in Brisbane. Austin was the latest in a long line of VIP visitors to the South Pacific nation this year, including French President Emmanuel Macron, Indian Prime Minister Narendra Modi, US Secretary of State Antony Blinken, New Zealand Prime Minister Chris Hipkins and UK Foreign Secretary James Cleverly. Australia’s Prime Minister Anthony Albanese was in Port Moresby too, in January, to progress a new bilateral security treaty.

The intensified interest is concomitant with PNG’s status as the standout among Pacific island countries in terms of territory, natural resources and population, giving it inherent leadership potential in a region that’s been rapidly rising up the international agenda.

Austin’s visit is strategically significant, because the centrepiece of the US’s invigorated bilateral engagement with PNG is a defence cooperation agreement, concluded in May. It has still to be debated in PNG’s parliament. The US State Department’s announcement on the agreement is couched in terms that underline the broad security benefits on offer to Port Moresby, including capacity building for the PNG Defence Force, disaster preparedness, and assistance to PNG’s small maritime constabulary force in suppressing illegal activities in the country’s vast sovereign archipelagic sea. The arrival of a US Coast Guard cutter to the region next year, with PNG ship riders onboard, should further the latter objective, helping to instil perceptions that greater US regional engagement contributes to security beyond narrow military considerations.

The White House appears cognisant of the need to engage Pacific leaders across a comprehensive definition of security, so that the offer of an elevated US defence partnership can be politically sustainable in PNG, increasing the likelihood of it achieving local support. Yet that need shouldn’t obscure the fact that PNG’s primary value to the US is a function of its strategic geography. The access negotiated under the agreement serves an underlying strategic purpose, integral to the US–Australia alliance, as the US Indo-Pacific Command reshapes its force posture in response to China’s continuing military build-up and prepares the theatre for the future possibility of armed conflict on a regionwide scale.

In June, with the ink on the agreement hardly dry, a flight of four US F-35 Lightning II aircraft en route from Australia to Hawaii diverted to Jacksons International Airport, in Port Moresby, for an unscheduled refuelling stop after the tanker they were meant to rendezvous with developed technical problems. The incident was a timely reminder of PNG’s potential as a defence partner in its own right, not simply territory to fly over or sail past.

The text of the PNG–US agreement reportedly identifies six sites for ‘unimpeded access’ across the country: the port and Jacksons International Airport in the capital; the port of Lae and Nadzab airport in the east; and the naval base at Lombrum on Manus Island and nearby civilian airport at Momote in the north. The agreement also details accommodation arrangements and the legal status of US military personnel deployed to PNG, the prepositioning of defence equipment and humanitarian supplies, and refuelling and maintenance for US ships and aircraft in transit. Its duration is 15 years, an indication of purpose on Washington’s part.

Austin has said the US is ‘not seeking a permanent base’ in PNG. In that, the agreement bears outward similarity to the recently expanded enhanced defence cooperation arrangement in the Philippines, with the obvious difference that PNG is not a US treaty ally.

The island of New Guinea, of which PNG forms the eastern half, is often depicted as sitting at the foot of the ‘second island chain’. Alternatively conceived, it constitutes the biggest link in Australia’s own first island chain. Either way, its importance is clear: it’s not just the closest country to the Australian mainland but, with an 820-kilometre land border with Indonesia, also the hinge between Southeast Asia and the southwest Pacific. The Torres Strait, between PNG and Australia, controls access between the Indonesian archipelago and the Coral Sea. Cape York, the northernmost part of the Australian continent, points directly to Guam, in the Marianas, America’s bulwark base in the second island chain. PNG is the only country in between. At AUSMIN, it was announced that Royal Australian Air Force Base Scherger, a ‘bare base’ located on the Cape, is likely to be upgraded, partly to meet US requirements.

From Washington’s standpoint, air and sea access through PNG helps to ensure that US forces can both disperse safely to Australia and project power freely from it into the western Pacific. Of course, Indonesia is also geographically vital in this regard, as an island screen across Australia’s Top End and northwest. Under international law, transit rights through Indonesia’s archipelago are guaranteed via designated sea and air corridors. Yet access in a crisis cannot be taken for granted, which gives PNG heightened significance as a reliable alternative. The Vitiaz Strait provides the most direct sea passage between the western Pacific and Australia’s eastern seaboard.

PNG’s geopolitical value is further sharpened by its sea boundary with Solomon Islands (a sensitive one for PNG, given uncertainty about Bougainville’s future status), which under Prime Minister Manasseh Sogavare is tilting towards China and remains one of Beijing’s most likely options to host a People’s Liberation Army presence in some form, even if it’s not a military base. Concern about restrictions that Honiara has imposed on some visiting US Navy vessels partly motivated Washington to negotiate a defence cooperation agreement with PNG.

Unit-level initiatives, such as Task Force Koa Moana, which integrates US marines and sailors with PNG defence personnel, suggest that the US military intends to forge lasting military-to-military and interpersonal relations within PNG. At the onset of a conflict or crisis, PNG could itself serve as a location for the US military to disperse combat assets from Guam and bases in the first island chain. In the event of a protracted maritime conflict, the US and Australia are both likely to regard PNG as a useful ‘in-theatre’ location from which to conduct combat replenishment, basic repairs and maintenance for ships and submarines, and possibly aircraft if the infrastructure is developed to support it. Lombrum served a similar function during World War II and could do so again, but with a smaller footprint on land. Comparisons with the 1940s, when Australians and Americans fought side by side with locals against Japan can mislead, but PNG’s positional importance in a US–China strategic context is likely to have fundamental resonances. Austin’s father served with the US Army in New Guinea during World War II, a point noted by PNG’s Prime Minister James Marape during their meeting.

Canberra has officially welcomed the PNG–US defence cooperation agreement. PNG’s rising strategic profile and that of the South Pacific in general are also discernible in the force posture elements of the AUSMIN communiqué. However, the invigorated US interest is likely to engender mixed feelings in Canberra, which for so long has seen itself as Port Moresby’s partner of choice. Australia’s defence cooperation program with PNG is its largest and the bonds run deep. Securing support for the US agreement has depleted Marape’s political capital, delaying the ratification of Australia’s own treaty-level agreement by several months. Nevertheless, the US decision to double down on defence cooperation with PNG stands to bolster Australia’s security significantly in the long run. It can be considered an extended investment in the US–Australia alliance, strengthening linear communications along the second island chain in particular, and facilitating access to and from Australia for US forces across the Pacific theatre.