Australia and Papua New Guinea agree on mutual defence treaty and vow joint response to attacks.

Australia and Papua New Guinea said on Sept. 17, 2025, they agreed on the text of the “Pukpuk” Mutual Defense Treaty, affirming that an armed attack on either would threaten both. The pact deepens interoperability across PNG facilities, the Bismarck Sea approaches, and its vast EEZ, with signing and ratification next.

The offices of Prime Ministers Anthony Albanese and James Marape confirmed on September 17, 2025, that Australia and Papua New Guinea have agreed on the text of the Pukpuk Mutual Defense Treaty. The communiqué recognizes that an armed attack on one would endanger the other and outlines plans to deepen operational cooperation and interoperability at designated PNG facilities, at sea in the Bismarck Sea approaches, and across PNG’s hard-to-police EEZ. It formalizes mutual-defense expectations in the Pacific and strengthens maritime security coordination pending signature and ratification.
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The HMPNGS Rochus Lokinap is a 39.5 metre Guardian Class Patrol Boat, designed and constructed by Austal Australia. (Picture source: Austal)

Papua New Guinea already fields several Guardian-class patrol vessels delivered under the Pacific Maritime Security Program. Designed and built by Austal in Western Australia, these steel ships are about 39.5 meters long, roughly 8 meters wide, and draw around 2.5 meters when loaded. Maximum speed is around 20 knots, with an endurance of approximately 3,000 nautical miles at 12 knots. A typical crew is just over twenty sailors, which aligns with available human resources. The hull and structure allow for a 30 mm gun on the foredeck and mountings for heavy machine guns on each side of the bridge.

The fleet has grown through successive deliveries, each entry into service accompanied by training and maintenance packages. The progressive replacement of the older Pacific Forum class was designed to limit skill gaps. The outcome is visible at sea. Countering illegal fishing, monitoring approaches, and conducting search and rescue. These repetitive tasks wear down hulls unless maintenance is followed precisely. This is where the treaty’s interoperability clauses have immediate use. Common procedures, harmonised communications plans, identical checklists from the bridge to the engine room, and regular exchanges of chief mechanics and watch leaders. Before adding a new sensor, these measures increase availability rates.

Behind these patrol vessels, infrastructure matters just as much. Lombrum Naval Base on Manus Island has been upgraded in stages with Australian and US funding for berthing, training, medical support, and small craft operations.

The communiqué also underlines the human factor. The idea of a recruitment pathway allowing Papua New Guinean citizens to join the Australian Defence Force has an obvious political dimension, but it addresses an operational need first. Strengthen support trades, logistics, and maintenance. Build transferable skills. Serving under Australian command avoids legal grey zones in a crisis, although Port Moresby will closely watch the risk of talent drain from a PNG Defence Force whose numbers remain modest. Unit level integration options, with mixed detachments and scheduled returns to the PNGDF, can reduce this risk while accelerating learning.

On the ground and at sea, the agreement should translate into more training and shared routines that look modest on paper yet affect outcomes. A regular exercise calendar, planned ADF access to identified sites in PNG, prepositioning of small stocks, and joint technical courses for mechanics, helmsmen, and radio operators. Guardian patrol vessels have a stern ramp to deploy and recover a fast boat. This is useful when a boarding team must depart within minutes and return safely in short swell. The electronic fit is standard for an ocean patrol vessel of this size. X band radar, VHF and HF systems, and digital charts. A shared doctrine and compatible parts enable sustained operations.

Overall, this does not point to a race for bases. It shows two countries seeking more reliable maritime governance while raising the cost of undeclared pressure. Patrol vessels with simple but durable armament. A base that trains, repairs, and returns ships to sea. A flow of Papua New Guinean recruits who acquire skills and sometimes bring them home. An exercise cycle that embeds itself in schedules rather than speeches. If funding continues and recruitment pathways are calibrated carefully, practical indicators should improve. More regular sorties, better prepared boardings, faster resolution of incidents.