as trans-Tasman defence relations get closer, NZ must be on guard

Anzac Day 2026 arrives in tumultuous times: unresolved conflict in the Middle East, the erosion of the old international order, the famous Doomsday Clock set closer to midnight than ever before.

Without doubt, this brings New Zealand’s defence relationship with its closest neighbour (and only formal ally) Australia into sharp focus.

In March, not long after the initial attack on Iran by the United States and Israel, closer defence relations with Australia were formalised under the Anzac 2035 commitment.

This essentially sets out to “operationalise” previous statements on closer defence relations, and reaffirms the importance of the ANZUS alliance – which also marks its 75th anniversary this year.

Given ANZUS became virtually defunct after New Zealand’s nuclear-free declaration in the 1980s, this is a remarkable turnaround. The vexed question of joining the AUKUS security pact aside, Anzac 2035 aims for a more cohesive and integrated combat-capable force.

This Anzac Day, then, it’s worth putting these latest developments in context. And it is important to understand the risks, as well as the rewards, of closer defence ties with Australia.

The origins of ANZUS

Trans-Tasman military cooperation is often thought to start with Gallipoli in 1915. In fact, it predates that pivotal moment by more than half a century when some 2,500 Australian men enlisted in militia units during the New Zealand Wars.

By 1887, the alliance was formally linked to Britain via a shared naval defence agreement. The Anzacs were born out of the two armies being fused in 1914 as they sailed for Egypt at the start of the first world war.

After the disaster of Gallipoli and the end of the war, New Zealand placed its faith in the peacekeeping role of the League of Nations. But as that began to collapse, Wellington turned again to its traditional friends.

During the second world war it became clear Britain could not protect its old colony, but the United States could. In 1944, New Zealand agreed to a regional zone of defence with Australia.

After the war, New Zealand supported the United Nations but also settled into the secretive Five Eyes intelligence-sharing relationship with Britain, Canada, Australia and the US.

In 1951, the ANZUS agreement with Australia and the US created a relationship based on “continuous and effective self-help and mutual aid” to “maintain and develop their individual and collective capacity to resist armed attack”.

Read more: Is NZ defence and intelligence policy aligning with AUKUS in all but name?

A freeze and then a thaw

By joining America’s wars in Korea and Vietnam, New Zealand was drawn closely into the US sphere of influence. But the Nuclear Free Zone, Disarmament, and Arms Control Act in 1987 saw the ANZUS treaty sidelined between Wellington and Washington – though never formally renounced.

Meanwhile, the relationship between Canberra and Washington remained watertight, and has only grown closer – albeit controversially – with the AUKUS security agreement and nuclear submarine deal.

New Zealand’s relationship with the US thawed after it sent troops to Afghanistan in 2001. By 2010, a new strategic partnership emerged with the Wellington Declaration on a New Strategic Partnership.

Since then, the old ANZUS partnership has been reinforced by contributions to the fight against Islamic State in Iraq in 2015, and help training Ukrainian troops in the war with Russia since 2022.

And while New Zealand has so far avoided committing to joining the security monitoring and intelligence sharing provisions of AUKUS Pillar II, it has arguably been moving in that direction anyway.

The government has also pledged to raise defence spending to more than 2% of GDP in the next eight years, and has been deepening military relationships with Britain, Japan, South Korea and the Philippines.

A challenging Anzac future

Set against the extreme uncertainty created by American foreign policy under President Donald Trump, New Zealand’s increasing focus on a reliable alliance with Australia makes sense.

There is certainly more that could be done to integrate further, including matching defence spending as a proportion of GDP with Australia’s intention to hit 3% by 2033.

And there remains the possibility of a genuinely combined military that improves efficiency, effectiveness and scale, with New Zealand perhaps becoming responsible for one fifth of a joint force.

But there has to be a caveat.

Given the large American military presence in Australia, there is a high chance those locations could be attacked in the event of a serious global conflict.

New Zealand will need to retain full sovereign control over any military it contributed to a future Anzac force. And it would have to remain committed to the multilateral United Nations model of conflict resolution wherever possible.

Any deepening of New Zealand’s military relationship with Australia also needs to be consistent with its commitments against weapons of mass destruction.

All of this means closely monitoring Australia’s far tighter relationship with the US, which will have serious implications for New Zealand – implications that are becoming clearer. Greater military cooperation with Australia is already happening – it needs to be eyes wide open.