Earlier this month, Australia, the United Kingdom, and the United States unveiled one of the most ambitious defense industrial partnerships in recent history: a submarine deal designed to equip Australia with nuclear-powered attack submarines (SSNs) as fast as possible. The deal consists of three unprecedented elements: an agreement by the United States to sell Australia three to five Virginia-class submarines beginning in 2032; the co-development of a new AUKUS-class submarine by the United Kingdom and Australia to enter service around 2040; and a multibillion-dollar pledge by all three countries to expand the capacity of a trilateral submarine industrial base.
But from the standpoint of deterring Chinese aggression within the next ten years, the most significant aspect of the deal was something else: a new trilateral submarine force posture initiative. This arrangement will see four U.S. Virginia-class submarines and one UK Astute-class submarine begin to make rotational deployments to Western Australia’s HMAS Stirling naval base from 2027. The move highlights how AUKUS, when combined with a new generation of U.S.-Australia force posture initiatives, can advance a strategy of collective deterrence on a much faster timeline than many expected. It also offers a window into the tectonic shift underway in the U.S.-Australia alliance as Canberra positions itself as a critical node in supporting high-end U.S. military operations to preserve a stable balance of power in an increasingly contested Indo-Pacific region.
Bolstering Near-Term Deterrence
The agreement, known as Submarine Rotational Forces-West (SRF-West), is by far the most important near-term contribution to strengthening deterrence vis-à-vis China in the AUKUS submarine construct. As a relatively fast-moving and operationally relevant endeavor, it stands in stark contrast to the extremely long-term AUKUS defense industrial project. Indeed, SRF-West is one of the most significant force posture initiatives advanced by the administration of U.S. President Joe Biden anywhere in the Indo-Pacific.
If all goes to plan, this trilateral effort could double the number of allied SSNs west of the international dateline by 2031, when SRF-West is supposed to reach its full component of forward deployed boats. Were Australia’s Virginia-class submarines to join it from 2033, as is widely expected, the overall laydown of SSNs could be even greater. It’s possible that by 2039—before Australia’s first AUKUS SSN is even in the water—there’ll be twenty-five allied SSNs on permanent or rotational deployment in Hawaii, Guam, and Perth.
Placing more attack submarines west of the dateline has long been a priority for U.S. Indo-Pacific Command. Doubling these numbers from five to ten over the next eight years is not only a major boost of a top-tier military capability. It’s also an incredibly rapid buildup, especially considering that it’s taken the United States over five years to grow the number of SSNs in Guam by just two boats.
The composition of SRF-West will do a lot to strengthen collective deterrence. As highly stealthy platforms, SSNs’ ability to operate in contested waters, hunt Chinese warships and submarines, control strategic sea lanes and chokepoints, and project power with long-range cruise missiles make them one of the most effective ways to complicate Chinese military planning and give Beijing a reason to take pause before using force. The fact that U.S., UK, and, in time, Australian SSNs will be operating as a combined force—with Aussies also embedded on American and British subs—raises the specter of horizontal escalation by forcing Beijing to consider the prospect that military action against any SSN, or the submarine base itself, could trigger the involvement of all three nations. London’s tangible commitment to this combined warfighting arrangement outside its traditional area of responsibility in the northern Atlantic underscores this aspect of integrated deterrence.
The location of SRF-West at HMAS Stirling also adds resiliency to collective deterrence efforts. It enables the dispersal of submarine forces more widely in the Pacific and provides a third base from which the U.S. Navy can operate. This will make it harder for China to track and target U.S. subs while cutting down the time it takes them to reach the western Pacific from Hawaii or the U.S. West Coast. What’s more, the Western Australian base is a kind of Goldilocks location: relatively safe from China’s long-range conventional missiles but close enough to potential flashpoints in the western Pacific and Indian Ocean to be operationally relevant and strategically significant.
There are, of course, a few assumptions baked into this equation. To avoid a numbers fudge, the four Virginias would have to come from homeports in the continental United States, rather than being deployed forward from Hawaii (where the U.S. has six Los Angeles-class and six Virginias) or Guam (where it has five Los Angeles-class). All five SRF-West submarines would have to rotate through HMAS Stirling at the same time—or else be substituted for Australia’s Virginias from 2033—to achieve a doubling of the west-of-the-dateline force. They’ll have to spend many months operating out of HMAS Stirling on each rotation to make the forward presence count strategically. And they’ll need Canberra to move very fast on its AUD $8 billion commitment to upgrade HMAS Stirling’s wharves, maintenance facilities, and logistics infrastructure to accommodate and sustain all these submarines by the end of the decade.
A Tectonic Shift in the Alliance
Although associated with the AUKUS deal, SRF-West is part of a much wider transformation in the character and purpose of the U.S.-Australia alliance—one that will see Australia play an increasingly pivotal role in actively supporting U.S. military operations as part of a strategy of collective deterrence.
This transformation has been hiding in plain sight. Motivated by a shared recognition of the need to shore up the regional balance of power amid China’s rising military might and the United States’ deteriorating strategic position, Washington and Canberra have been quietly rewiring the alliance through a series of new initiatives under the 2014 Force Posture Agreement. This process was rapidly accelerated by an historic, albeit largely overlooked, decision at the 2021 Australia-United States Ministerial Dialogue to double down on enhanced force posture cooperation across five key areas: four service-based initiatives involving the Australian Defence Force (ADF) and the U.S. Air Force, Marine Corps, Navy, and Army, and a cross-cutting logistics, sustainment, and maintenance enterprise “to support high-end warfighting and combined military operations in the region.”
These posture arrangements are intended to reinforce the United States’ military position in the Indo-Pacific by leveraging Australia’s strategic geography, geopolitical alignment, and capacity for high-end military integration. Through the Enhanced Air Cooperation initiative, for example, Canberra and Washington are developing the airfields, fuel depots, prepositioned weapons stores, and habits of interoperability required to operate U.S. Bomber Task Forces out of northern Australia. Elsewhere, through the annual rotation of around 2,500 U.S. Marines to Darwin, the ADF is honing its ability to support and deploy with Marine expeditionary units as they implement new operational concepts to rapidly deploy precision strike capabilities in contested littoral environments. Both aim to enhance collective deterrence in the near-term by dispersing U.S. forces, integrating U.S. and Australian personnel, and creating new attack vectors and targeting problems for Chinese planners.
Seen in this context, SRF-West is the latest in a series of combined force posture initiatives and the first in the new Enhanced Maritime Cooperation arrangement. And like its Air Force and Marine Corps equivalents, it’s about more than just hosting U.S. and UK assets. It will also leverage the ADF’s growing ability to sustain, maintain, and integrate with these forces. As recent submarine exercises at HMAS Stirling reveal, Australian personnel will play an increasingly integrated role in replenishing allied SSNs, rearming their cruise missile cells, and working closely with U.S. submarine tenders. Moreover, as Australia’s SSN infrastructure develops, HMAS Stirling will likely emerge as a full-spectrum trilateral submarine operating hub for everything from forward-based maintenance, repair, and overhaul to coordinated mission planning and sustainment.
This growing suite of force posture initiatives is propelling the U.S.-Australia alliance into uncharted terrain. While the ADF has a long history of fighting shoulder-to-shoulder with U.S. forces, Australian bases have never been directly integrated into U.S. war plans. Nor, at least since World War II, have they been used as a staging post for U.S. military operations. This is now fundamentally changing. Australia will soon be the only ally in the world to host and support military operations by forward-deployed U.S. strategic bombers and SSN attack submarines, and it’s fast becoming a hub for other forms of power projection. As these new force posture initiatives mature and become more central to American plans, U.S. warfighters will not only be reliant on Australian bases, infrastructure, logistics, and prepositioned equipment. They’ll also come to depend on ADF personnel and military platforms for a wide range of supporting, auxiliary, and operational roles as part of a combined effort to preserve the regional balance of power and deter Chinese aggression.
Managing this shift will be a challenge for both sides. Unlike NATO and other American alliances, the United States and Australia do not have highly developed mechanisms for coordinated military planning and are yet to flesh out how they might collectively allocate roles, missions, and capabilities to deter and respond to high-end security threats. SRF-West and other posture arrangements will need to address this issue head on. Both sides must also come to terms with the political reality that posture integration is a two-way street. By making the sovereign decision to host a robust U.S. warfighting presence on Australian soil, Canberra has made a very clear commitment about supporting Washington in a regional crisis. But it has also bought itself a degree of insight and influence over U.S. military plans—and enough skin in the game to shape them constructively. All of this knot-tying, precisely because it is difficult, adds to the credibility of allied resolve.
Beyond the historic AUKUS submarine deal, these are the unseen mechanics of alliance integration that will bring to life a strategy of collective deterrence. By boosting the number of SSNs in the Pacific in a strategically relevant timeframe and by building out the maritime component of a transformative force posture agenda, SRF-West will make a real contribution to deterring Chinese aggression. Far from being an adjunct to AUKUS or an isolated submarine arrangement, SRF-West is a microcosm for how Washington and Canberra are transforming their alliance to defend the Indo-Pacific order—and a harbinger of more combined posture initiatives to come.