If there’s a war in the Pacific, who defends Australia?

29 August 2025 | Jennifer Parker

*Originally published in the Sydney Morning Herald on 29 August 2025

Image: HMAS Sydney transits as part of the double carrier formation, UK Carrier Strike Group, led by HMS Prince of Wales and US Navy’s George Washington Carrier Strike Group, during Exercise Talisman Sabre 2025. (Defence Images)

With Defence Minister Richard Marles back from a mysterious trip to the US, the alliance is back in the spotlight, as it has been since the second Trump administration took office. This week we debated whether Marles’ photo with US Secretary of Defence Pete Hegseth represented a “happenstance” or a “meeting”, an issue that represents the chaos in the Pentagon rather than a reflection on the alliance. Yet beneath the headlines lies a more pressing question: in a crisis, how would we fight together in an Indo-Pacific conflict, are our expectations of roles clear and are they truly in Australia’s interest?

I would argue they are not. Australia should focus on complementing US power while retaining the ability to execute key roles independently, from defending Australia and its maritime trade to supporting partners in the Pacific without relying on Washington. After all, as a sovereign nation, Australia alone is responsible for its defence.

This debate has sharpened with reports that the Pentagon’s undersecretary of defence for policy, Elbridge Colby, is pressuring Australia to clarify its role in a potential conflict over Taiwan. While suggestions of demands for a formal pre-commitment seem unlikely, especially given Washington’s own policy of strategic ambiguity, it is clear the US wants greater certainty. Australia should want that clarity too.

Long a cornerstone of Australia’s military strategy, the alliance has allowed a nation of 27 million to wield disproportionate influence in an era of great-power competition. Despite tensions over the US review of AUKUS and calls for higher defence spending, co-operation between Canberra and Washington has reached levels not seen since World War II, from a surge in force posture initiatives to the growth in military exercises and exchanges.

Australia’s 2024 National Defence Strategy notes that “Australia’s alliance with the US is fundamental to our national security and the ADF’s capacity to generate, sustain and project credible military capability”. While true, it prompts a critical question: in a crisis or conflict in the Indo-Pacific, would that power be projected as part of a US-led force, with Australian units integrated into American command, or in a complementary role with clearly defined missions, responsibilities and geographic areas? Who is responsible for defending Australia?

This is more than semantics; it goes to the heart of who controls the employment of Australian ships, aircraft and other capabilities, and how we design and operate the ADF.

The question of integration of forces versus delineation of forces becomes even more pressing given that, in any Indo-Pacific conflict, Australia would be fighting from its own territory for the first time since WWII. This represents a profound cultural shift, highlighted by Chief of Defence Force Admiral David Johnston, who noted earlier this year that “perhaps finally we are having to reconsider Australia as a homeland from which we will conduct combat operations”.

Australia often underscores its reliability by noting that Australian and American forces have fought side by side in every major conflict since the Battle of Hamel in WWI, from Europe to Iraq and Afghanistan. This history can create the impression that operating together is a well-trodden path. At the tactical level, that’s true. But strategically, the conflicts of the past differ markedly from those we may face in the future.

Australia built its force contributions to fight and, when required, to sacrifice on distant shores, where the defence of the continent was never in question and Australian civilians were never directly at risk.

The only time Australia fought alongside the US with its own defence and civilian population at risk was during the Pacific campaign of WWII. After the fall of Singapore, a vulnerable Australia turned to Washington for protection, placing its forces under US General Douglas MacArthur’s command. While that arrangement proved successful, Australia today is a different nation. It has long since shed the constraints of empire, formalised by the 1986 Australia Act, and now boasts a far more diverse population, with 31.5 per cent of Australians born overseas.

Australia in 2025 is far less willing to hand control of its naval, air and land forces and its defence to a US commander, and rightly so. But does Washington see it that way? It’s a critical question, especially with the growing presence of US marines, bombers and submarines on Australian shores, all of which will need protection.

The harder truth, however, is that Australia has neither funded nor designed its ADF to independently defend the continent or execute key missions without US support. From a lack of sovereign space capability to limited missile defence and a stretched navy, the gaps are stark. Investment in nuclear-powered submarines and a larger surface fleet is a start, but real sovereignty requires more, a clear strategy and a force design built around Australia’s own defence and regional roles. It should be designed to be supported by the US in our defence, not in support of the US defending us.

The Australia–US alliance is, rightly, a cornerstone of Australia’s defence strategy and efforts to deepen co-operation with Washington have been vital. But as states increasingly turn to force to settle disputes, a stronger alliance depends on both partners having a clear understanding of each other’s expectations. Roles and responsibilities must be clearly defined.

To preserve its autonomy, Australia must articulate and fund a strategy that clearly delineates responsibilities, rather than continuing to field a force built to be employed under US command, as it has in past conflicts.