Australasia is covered by overlapping alliances, intelligence partnerships and regional declarations. Understanding how they fit together is increasingly important as strategic competition reaches deeper into the Pacific.

There is no single military alliance responsible for the defence of Australia, New Zealand and the Pacific Islands.

Instead, regional security rests on a network of treaties, partnerships and political commitments. Some are formal defence arrangements. Others concern intelligence, policing, maritime surveillance, disaster relief or collective consultation.

Together they form the region’s security architecture.

ANZUS

The Australia, New Zealand and United States Security Treaty was signed in 1951 and entered into force in 1952.

It committed the three countries to consult and cooperate on security in the Pacific. The treaty remains the foundation of Australia’s defence relationship with the United States.

New Zealand’s role changed substantially during the 1980s following disagreement with the United States over nuclear-powered and nuclear-armed vessels.

ANZUS continues to exist, but in practical terms Australia and the United States maintain the treaty alliance, while New Zealand has rebuilt extensive security cooperation with both countries through other arrangements.

AUKUS

AUKUS brings together Australia, the United Kingdom and the United States.

Its best-known component is the plan to provide Australia with conventionally armed, nuclear-powered submarines. It also covers cooperation in advanced technologies, including artificial intelligence, cyber capabilities, quantum technologies, undersea systems and hypersonics.

AUKUS is not a general Pacific collective-defence treaty. It is a strategic and technological partnership designed to strengthen long-term deterrence and military capability.

Five Eyes

Australia and New Zealand are members of the Five Eyes intelligence partnership with the United States, United Kingdom and Canada.

Its origins lie in signals-intelligence cooperation, but the relationship now supports broader exchanges of intelligence and security assessments.

Five Eyes does not operate like NATO. There is no automatic collective-defence clause binding all five countries to enter a war together.

Its significance comes from the depth of intelligence sharing between trusted partners.

The Five Power Defence Arrangements

The Five Power Defence Arrangements connect Australia, New Zealand, the United Kingdom, Malaysia and Singapore.

Established in 1971, the arrangements require consultation if Malaysia or Singapore faces an external attack or threat.

They do not automatically compel military intervention. Their continuing value lies in joint exercises, military interoperability and sustained defence relationships across Southeast Asia.

Pacific-led security

Pacific Island nations have repeatedly argued that regional security must be defined more broadly than military competition.

The Boe Declaration on Regional Security recognises climate change as the greatest threat to the livelihoods, security and wellbeing of Pacific peoples. It also encompasses human security, cybersecurity, transnational crime and environmental pressures.

This broader understanding is important.

For a low-lying island state, rising seas, a cyclone, illegal fishing or the failure of critical communications may be more immediate than the possibility of conventional warfare.

Bilateral agreements are increasing

Australia and New Zealand also maintain individual security relationships with Pacific countries.

These may cover:

• Maritime surveillance
• Police cooperation
• Defence training
• Border protection
• Infrastructure
• Cybersecurity
• Disaster response
• Peacekeeping
• Unexploded wartime ordnance

New agreements are likely as competition for influence increases.

China has pursued security and policing relationships in the Pacific, while Australia, New Zealand, the United States, France and Japan have expanded their own engagement.

What may come next?

A Pacific version of NATO remains unlikely.

Pacific nations differ greatly in size, geography, military capability and foreign policy. Some do not maintain armed forces at all. Many resist being forced to choose between China and Western partners.

The more plausible future is a stronger network of overlapping agreements.

Australia and New Zealand will remain central defence partners, but regional legitimacy will depend on whether Pacific governments help define the objectives.

Security cannot simply be delivered to the Pacific by larger powers. It must be developed with Pacific countries and shaped by their understanding of what threatens their people.