Will AUKUS Pay Major Dividends in a Taiwan Contingency?

In March this year, the trilateral security partnership between Australia, the UK, and the U.S., known as AUKUS, unveiled its phased plan to provide Australia with nuclear-powered attack submarines (SSNs). This will involve the U.S. selling Australia Virginia-class SSNs in the early 2030s, followed by a new class, the SSN-AUKUS, being built for Australia in the late 2030s.

While China has not been directly mentioned in AUKUS announcements, it is the clear target of the partnership’s declared aim to “strengthen deterrence and bolster stability in the Indo-Pacific." In Washington, there is growing concern that deterrence is eroding across the Taiwan Strait and that China may soon be confident enough to invade Taiwan. To bolster deterrence, the Biden administration has attempted to signal to China that there could be a combined allied defense to preserve the status quo; a strategy that could perhaps be termed ‘collective strategic ambiguity’. The administration has released a number of joint statements with numerous U.S. allies, including Australia, in which they reaffirm the importance of maintaining peace and stability across the Taiwan Strait and their shared opposition to unilateral changes to the status quo. That said, Australia has been non-committal as to whether it would actually help defend Taiwan.

While acquiring SSNs would allow Australia to deploy submarines in a Taiwan contingency, this does not necessarily mean it will. A review of some of the operations Australia’s SSNs are well suited for in a conflict with China over Taiwan illustrates why the U.S. may be unable to firmly count on AUKUS to pay major dividends in a crisis. This is due to the confrontational nature of these operations, which could make Australia hesitate to make good use of its SSNs.

Australia could harness its SSNs’ torpedoes, speed, and stealth for anti-submarine warfare (ASW) against China’s fleet of attack submarines (both SSKs and SSNs). China could use those subsurface forces to put U.S. carrier battle groups operating around Taiwan, which would be key to a U.S. defense of the island, at significant risk. Importantly, using SSNs to conduct an ASW mission against China could result in Australia threatening China’s ballistic missile submarines (SSBNs), the sea leg of China’s nuclear deterrent. This is because if Australia sunk China’s attack submarines, which protect China’s SSBNs, this would make the latter significantly more vulnerable. Moreover, if Australia hunts China’s attack submarines, it could inadvertently sink some of China’s SSBNs. This is because they will likely be closely accompanied by China’s attack submarines for protection, which makes target differentiation difficult. As Georgetown Professor Caitlin Talmage observes, those kinds of attacks may appear to Chinese leaders as an attempt at softening up China’s nuclear forces for a U.S. nuclear counterforce strike. This could raise the risk of inadvertent nuclear escalation, as degrading China’s nuclear forces might confront Chinese leaders with a ‘use-or-lose’ dilemma, whereby they could be incentivized to go nuclear – before they no longer can – to make the U.S. and its allies back down.

If Australia is unwilling to risk threatening China's sea-based nuclear forces due to concerns of inadvertent escalation, it may well hesitate to use its SSNs to conduct an ASW mission in a Taiwan contingency. Australia may also be cautious over intervening simply given the severe asymmetry in military power between it and China. Come 2030, when Australia should begin acquiring SSNs, the U.S. Department of Defense expects that China could possess 1,000 nuclear warheads. Although Australia is a U.S. ally and China has a no-first-use nuclear policy, Australia could still be highly risk-averse. American observers have long doubted the sincerity of China’s no-first-use policy, especially in a major crisis over one of its so-called “core interests.” Such concerns may foment in Australia too. As the White House Coordinator for the Indo-Pacific Kurt Campbell recently admitted in December last year, in light of China and North Korea’s nuclear buildups, the “reassuring quality of our extended deterrence of our nuclear umbrella” is “being challenged now."

Australia could also use its SSNs for land-attack operations in the South China Sea, as the Virginia class SSNs that Australia will first acquire through AUKUS are equipped with a vertical launch system (VLS) for firing land-attack Tomahawk cruise missiles. The SSN-AUKUS that Australia will later acquire will likely field a similar VLS capability. Australia could consequently use its SSNs to blanket strike thousands of acres of military infrastructure across China’s island bases in the South China Sea, which includes surface-to-air missiles, anti-ship cruise missiles, runways, and radar facilities. In a Taiwan contingency, China might use these island bases to try and establish control of the South China Sea to create a safe bastion for its SSBNs by preventing U.S. surface ships and ASW aircraft from operating in the region. This added security for its sea-based nuclear forces may embolden China in a crisis, as it could better counter U.S. threats of nuclear escalation. This would be an ideal mission for Australia’s SSNs, as it would reduce operational demands on U.S. forces. As Gregory Poling of the Center for Strategic and International Studies (CSIS) observes, in a Taiwan contingency, the U.S. would likely divert its important naval platforms, like its SSNs, to Northeast Asia.

For Australia to attempt to deny China enhanced security for the sea leg of its nuclear deterrent, Australia would have to use its SSNs to strike what China considers its sovereign territory. As documented by Stanford professor Oriana Skylar Mastro, official Chinese government sources consistently refer to the South China Sea as China’s “inherent territory” and has “historically been part of China’s territory”; phrases often used in reference to Hong Kong, Taiwan, Tibet, and Xinjiang. Chinese leader Xi Jinping has also repeatedly vowed to defend China’s perceived sovereignty and relevant rights in the South China Sea in bilateral meetings and at multilateral summits. This means that China has strong incentives for a forceful response to attacks on its island bases, which could well make Australia hesitate from striking them. Come 2035, when Australia should be fielding several SSNs, the U.S. Department of Defense expects China to possess 1,500 nuclear warheads. In the face of such a difference in military power, Australia could well be deterred from using its SSNs to attack China’s island bases.

AUKUS is a worthy initiative to modernize Australia’s armed forces amidst an increasingly dangerous security environment. As the Australian government’s recent Defense Strategic Review concluded, Australia’s “current force structure is not fit for purpose for our current strategic circumstances." But while it is hard to argue that AUKUS will not help to bolster Australia’s defensive capability, the extent to which the U.S. can fully count on Australia to use AUKUS to go ‘all in’ and pay major dividends in a Taiwan contingency is less clear.

Rupert Schulenburg is an analyst focusing on Indo-Pacific security, U.S. alliances and force posture, as well as U.S.-China competition. He holds an MPhil in International Security Studies from the University of St Andrews and a BA (Hons) in International Relations from the School of Oriental and African Studies (SOAS), University of London. He is the author of the forthcoming chapter “Alignment choices in an era of U.S.-China competition: Navigating a Taiwan contingency and trade relationships” (Springer, 2023).