Australia and Papua New Guinea (PNG) elevated their security partnership in early October 2025 by signing the Papua New Guinea–Australia Mutual Defence Treaty, colloquially known as the “Pukpuk Treaty”.

The agreement marks Australia’s first new formal defence alliance in more than seven decades and represents PNG’s first-ever mutual defence pact.

Under the treaty, both nations commit to assist one another should either face an armed attack, signalling a deepening of Canberra’s role as a regional security partner and a new chapter for PNG’s defence arrangements.

One of the most notable provisions allows up to ten thousand Papua New Guineans to serve in the Australian Defence Force under dual-service arrangements.

On 20 October, the respective defence ministers held the first ministerial implementation meeting in Canberra, launching the pathway from “defence partners to allies”.

The discussions covered mechanisms for consultation, enhanced interoperability, access arrangements and the modernisation of PNG’s defence capacity.

Australia’s Department of Defence described the meeting as a key step in giving effect to the treaty.

Despite the fanfare, the work ahead is considerable.

Analysts point to diverging geostrategic priorities: Australia emphasises countering growing Chinese influence in the Pacific, while PNG emphasises sovereign capacity, humanitarian readiness and maintaining broader partnerships, including with regional powers.

Some commentators suggest these differences could complicate rollout of joint facilities, personnel arrangements and operational protocols.

Further, the treaty text emphasises that both nations should refrain from agreements with third parties that would “compromise” the pact’s implementation—an indirect reference to China-Pacific security engagements.

While both leaders publicly reaffirmed that the treaty is grounded in geography and history rather than geopolitics, the proximity of Beijing’s security outreach in PNG has cast a shadow over the alliance’s regional context.

Implementation challenges extend to logistics, funding and capacity.

PNG’s defence force is relatively small, and building the infrastructure, training pipelines and institutional systems required for full alliance integration will take years.

Australia has committed to support capability enhancements, training and infrastructure in PNG, but domestic fiscal and political constraints may affect pace and scale.

In PNG, sensitivities around sovereignty and external influence remain politically salient, meaning Canberra must tread carefully to advance cooperation without provoking nationalist or regional push-back.

The Pukpuk Treaty thus stands as a milestone in Pacific security architecture, but its enduring impact will depend on timely, sustained implementation—both operationally in defence arrangements and politically in maintaining PNG’s equidistant posture amid great-power competition in the region.