Debate on Australia’s defence strategy often centres on the budget and the plan to acquire nuclear-powered submarines. The anticipated signing of what Papua New Guinea’s defence minister has called a ‘mutual defence’ treaty underscores this point, highlighting the renewed focus on a neighbour whose security is inseparable from Australia’s own. The signing of a defence treaty between Australia and PNG is about more than countering China’s influence. A mutual defence treaty would typically imply an obligation to respond to an attack on either party, akin to NATO’s famed Article 5: an attack on one is an attack on all. While it is unlikely to amount to a full mutual defence pact or a fully integrated force, it is a clear sign that Australia’s regional defence strategy is beginning to bear fruit.