Australia and the US nuclear umbrella: from deterrence taker to deterrence maker

ABSTRACT Historically, Australia's approach to extended nuclear deterrence can be seen as a consumer rather than contributor within the framework of its alliance with the United States. Despite invoking the nuclear umbrella in strategic guidance since the early 1990s, successive Australian governments have been reluctant to engage with operationally supporting extended nuclear deterrence and content to point to the Joint Facilities as evidence of Australia's contribution. The changing nature of the Indo-Pacific strategic balance means that this approach is increasingly misaligned with contemporary strategic risks and Australia's evolving strategic focus on deterrence. The recent intensification of defence and force posture cooperation between Canberra and Washington presents a window of opportunity for Australia to redefine its approach to the nuclear umbrella in the context of a more holistic understanding of mutual commitments in the alliance. This article outlines how Australia should bolster its contribution through more structured dialogue with the US on nuclear strategy and mutual expectations, supporting preparation for and potential execution of US nuclear operations in the Indo-Pacific, and returning to a formal position of opposing the Treaty on the Prohibition of Nuclear Weapons.


Introduction
Since the 1970s, Australian defence policy has been based on three complementary elements.The first is support to the United States, which has grown over time given the increasing importance of US intelligence, defence technology and industry to Australia's own defence.The second element is 'self-reliance' regarding the ability of Australia to conduct conventional operations in its own defence without relying on US combat forces for support.The third element has been Australia's defence engagement with countries in Southeast Asia and the South Pacific that stops short of formal alliance commitments but seeks to promote Australia as a security partner with common interests in the eyes of the region.In combination, these three elements confirmed a significant break from the 1950s and 1960s, when Australia had based its defence policy on building multilateral alliance architecture aimed at deterring and defending against communist expansion in Southeast Asia: ANZAM with the United Kingdom and New Zealand, ANZUS with New Zealand and the United States, and the Southeast Asian Treaty Organization (SEATO).
In this context, US extended nuclear deterrence often seemed like a vestige from the past, which did not sit easily with the overall precepts of post-Vietnam strategic policy (Fruḧling 2013).This was certainly the argument of those in Australia who felt it should follow in New Zealand's footsteps and disavow nuclear deterrence, even if at the cost of the US alliance.But without a desire to give the US alliance a greater role in the defence of Australia, and in the absence of a clear direct nuclear threat beyond the general Cold War confrontation with the Soviet Union, Australian governments did not see a need to accord prominence or substance to US nuclear guarantees under the alliance.Hence, it was not until 1993 that public strategic guidance documents started to refer to extended nuclear deterrence for Australia, and only then with reference to protection against nuclear threats.Indeed, the only reference to US extended deterrence in the recent unclassified version of the Defence Strategic Review (DSR) is exclusively through a nuclear threat lens: In our current strategic circumstances, the risk of nuclear escalation must be regarded as real.Our best protection against the risk of nuclear escalation is the United States' extended nuclear deterrence, and the pursuit of new avenues of arms control.(Department of Defence 2023, 37) Today, the underlying principles of Australian defence policy are shifting towards a more integrated, multilateral, and explicit regional deterrence architecture.This is reflected in the increasing use of Australia as a base area for US military operations, closer alignment and military cooperation with Japan and other US allies in the region, and the identification of deterrence as the lodestar of Australian defence and alliance cooperation.This shift stems from a growing realisation in Canberra over the past half decade that China is intent on using its ability to project substantial combat power across the Indo-Pacific to widen its political influence and, if need be, use force to change the status quo on the ground.This has been reinforced by Beijing's ambitious nuclear weapons modernisation program, which has seen the expansion of China's capacity to hold a wide range of regional targets at risk during any crisis.
Against this background, it is time to re-think the role of nuclear deterrence in Australian defence policy.If US nuclear weapons have been of limited relevance to Australia in the past because it did not see itself as a deterrence taker, Australia's shifting defence policy requires Canberra to view the role of nuclear weapons from the vantage point of Australia as a regional deterrence maker.We argue that bolstering Australia's contribution to extended nuclear deterrence is in the country's interest because it will strengthen overall the robustness of the US nuclear umbrella in the Indo-Pacific.This will, in turn, promote two inter-related aims in Australian strategic policy: firstly, reinforcing the non-nuclear weapon status of US allies Japan and South Korea, thus contributing to regional non-proliferation; and secondly, buttressing the credibility of Washington's commitment to deterring Chinese coercion in the Indo-Pacific.
The article is divided into four sections.In the first section we provide a brief overview of the nature of commitments and deterrence in alliances, drawing on the alliance literature.The second section outlines the changing landscape of the Australia-US alliance and argues that this creates the conditions for re-imagining how Australia can contribute to the US nuclear umbrella as part of the bilateral alliance.In the third section, we assess how extended nuclear deterrence has evolved in the Australia-US alliance since it was incorporated explicitly into Australian strategic guidance in the early to mid 1990s.The final section proposes several initiatives that Australian governments should consider with a view to strengthening the country's contribution to extended nuclear deterrence, which will promote Australia's regional balancing strategy and deterrence posture while contributing to the maintenance of regional security.

Alliances, commitments, and deterrence
Alliances tend to reinforce inequality by formalising power differentials between major powers and junior partners.They also raise the risks of entrapment where one party is dragged into a conflict due to mutual treaty commitments to defend the ally irrespective of the circumstances that trigger war (Snyder 1997, 181-183).However, what alliances take with one hand in constraining sovereignty, they can deliver with the other in multiplying security assurances against hostile states.Alliances can provide junior partners with greater agency in international relations by elevating their interactions with major powers, while smaller states often benefit from being able to keep defence spending lower than it would otherwise need to be without an alliance.
When they are struck, alliances are designed to institutionalise commitments between states whose overall interests and preferences will change over time (Walt 1997).'Knowing this', as Iain Henry (2022, 122) has suggested, 'national leaders and defence planners should constantly monitor their ally, regularly assess the strength of their alliance, and wonder about its future strength as well'.Alliance commitments pertain to using force to defend the other alliance member as enshrined in formal treaty obligations; sharing the costs of maintaining the alliance, codified usually in a status of forces agreement if the major power stations military personnel and platforms on the territory of its ally; and procedures for decision making in managing the alliance-from consultation over basing arrangements through to authorising the activation of nuclear weapons in defence of alliance members.
Countries sign up to alliances in the knowledge that this entails commitments, the nature of which will not remain static.With notable exceptions, alliances formed in the post-war period have been highly responsive to the changing interests and preferences of member states.In other words, most alliances most of the time are effective at adapting to the changing preferences of members.This is not simply a case of smaller states accommodating the preferences of the major alliance partner.There remain many cases in the history of NATO and in America's Indo-Pacific alliances where Washington has adjusted its policy settings on sensitive issues like nuclear weapons in response to the political and strategic concerns of non-nuclear allies (Fruḧling and O'Neil 2021).
Like interests, the type of contributions made by individual states within alliances evolves over time.As Tongfi Kim (2016, 28) notes: 'The goals of alliances vary across cases and time, but states participate in military alliances to obtain efficiency gains, regardless of their specific goals'.From the vantage point of junior allies, this goes beyond the formal provisions of a security treaty.The Clinton administration's decision to exert economic pressure on Indonesia in 1999, despite Washington's long-term interest in preserving a positive bilateral relationship with Jakarta, was aimed at smoothing a pathway for Australian leadership of the INTERFET force in East Timor in September that year (Stockings 2022, 295-303).
Alliances privilege structure over agency in the search for greater order and stability in an uncertain world.But because states' interests and preferences change over time, alliances are invariably characterised by an underlying uncertainty about commitment: Protégés fear that their patron may abandon them rather than fight a costly war on their behalf, while the patron fears that protégés may chart a more independent and less deferential foreign policy course if they outgrow their dependence on its protection.(Blankenship 2020(Blankenship , 1019) ) The core commitment in alliances lies in the terms and conditions of the security treaty between parties, but alliance commitments are not just about narrow treaty obligations; the more institutionalised alliances become, the greater the prospect for formal and regular channels for consultation on matters of substance to the junior partner (Rafferty 2003, 344-345).Such consultative mechanisms can encourage informal expectations on both sides about commitments that go beyond narrow treaty obligations.Quite often, the most salient alliance commitments 'are those that bind the state to take some set of actions that do not look to be in its narrow self-interest as an international actor' (Taylor Gaubatz 1996, 111).
Commitments can be stated publicly, such as those provided by major power allies in response to threats by adversaries against junior allies.Typically couched in the form of extended deterrence, this commitment is aimed just as much at reassuring junior allies and preventing undesirable behaviour like nuclear proliferation, as it is about persuading adversaries not to engage in threatening behaviour.From the perspective of junior allies, these verbal commitments carry more weight when they are issued publicly rather than behind closed doors because the act of announcing places the patron's credibility on the line and makes reneging considerably less attractive than it would have been otherwise.While the verbal commitment is not costly to make, the patron stands to suffer significant reputation costs down the line if it fails to meet its alliance obligations.(Fuhrmann and Sechser 2014, 922) Commitments remain at the heart of alliance management, but these can be perceived differently by countries in the same alliance.As Glenn Snyder (1997, 169) writes, Commitment is a matter of degree rather than absolutely either-or: although sometimes states will feel themselves to be either committed or not, more often they will be somewhat uncertain about how they will act when the time comes for the commitment to be honoured; estimates of a partner's commitment will be even more uncertain and probabilistic.
The case of Australia's behaviour in relation to a potential future commitment to support a US defence of Taiwan is illustrative.While Australian support in such a scenario is widely assumed, senior Australian policy makers have been reluctant to indicate that this commitment would be forthcoming.

Extended deterrence, nuclear weapons, and the Australia-US alliance
The Australia-US alliance is idiosyncratic insofar as both countries have traditionally avoided formal discussion of their treaty commitments and how these relate to specific scenarios (Fruḧling 2018).Where this has taken place, such as during the early 1960s when Australia feared armed conflict with Indonesia, interactions have been awkward and occasionally fraught from Canberra's perspective.The Menzies government's attempt to extract a commitment from the Kennedy administration regarding the specific circumstances in which the US would intervene in an Australia-Indonesia conflict was rebuffed in Washington (Edwards 1992, 265).This contrasted with the Clinton administration's informal private assurance to the Howard government in 1999 that US military support would be forthcoming should Australia find itself in armed engagement with Indonesian forces as part of Canberra's leadership of INTERFET (Stockings 2022, 296).
Although cooperation between Australia and the US has grown in key areas such as intelligence sharing, military exercises and operations, and defence acquisition and sustainment, the detail of binding security commitments remains vaguely defined.This is despite expectations in Australia of alliance support and official declarations of the close bonds in the alliance intensifying over time.While Australia chose to invoke Article V of ANZUS after the 2001 terrorist attacks on the US, successive Australian governments have been wary of specifying the circumstances in which formal treaty obligations would be activated in the alliance.Notwithstanding Taiwan's status as a democracy and growing US commitment to defending the country's sovereignty against Chinese aggression, with very few exceptions (Bramston 2021) Coalition and Labor governments have been ambivalent about whether Australia's ANZUS treaty obligations would align with supporting the US in a conflict against China over Taiwan.
Yet, the US has also been hesitant to outline specific circumstances in which it would come to Australia's defence under the ANZUS treaty.This is understandable because historically there has been no direct or immediate threat from major powers to Australian security, juxtaposed with Soviet/Russian threats against NATO members and North Korean sabre rattling directed at South Korea and Japan.Notwithstanding this, the lack of engagement with Australia on scenarios where military support from Washington would be activated remains an anomaly in US alliance management.Overall, Australian governments have continued to endorse the logic stated in the 1976 version of the classified Strategic Basis paper that Australian defence policy regarding the US[…]has two primary objectives.The first is to maximise Australia's long-term influence on US policy, so as to enhance the prospect of US support in an Australian defence emergency.The second is to support US activity for the deterrence and containment of the USSR, and any other power that might offer threat to Australia.(Defence Committee 2009, 602) Beginning with the Hawke government in 1984, Australia has pointed to its support for nuclear deterrence through hosting the Joint Facilities as a key contribution it makes to the alliance; these facilities help to provide early warning of an attempted first-strike by adversaries (Ball 1989).In a parliamentary speech in 2019, then Defence Minister Christopher Pyne (2019Pyne ( , 1088) ) noted that: Australia is not only a beneficiary of the US policy of extended nuclear deterrence, it is an active supporter of it, through our joint efforts with the US at Pine Gap and at other facilities, such as the Naval Communication Station Harold E Holt, and the Joint Geological and Geophysical Research Station.
In practice, however, successive Australian governments have been deliberately circumspect in discussing how Australia should be contributing to US extended deterrence in an operational sense.In 2019, the conservative Morrison government responded to a public suggestion by then US Defence Secretary Mark Esper that the US could look at stationing intermediate range missiles in Asia by quickly ruling out any potential for basing the systems in Australia (Johnson 2019).More recently, the Albanese government has focused on playing down any nuclear mission for US B-52s operating from Australian shores (Greene 2023).While these moves have no doubt been made with domestic politics in mind 1 and confirm a junior ally's preference to have its cake and eat it when it comes to the nuclear umbrella, Australia's public reluctance to contribute to the nuclear umbrella beyond parliamentary references to the Joint Facilities underscores a gap between broad declaratory policy and operational level commitments.
In declaratory terms, Australia's current position on extended deterrence has its origins in the 1993 Strategic Review, which lay the groundwork for the 1994 Defence White Paper.The Keating Labor government codified a 'sole-purpose' approach to US extended deterrence-Australia would only look to the activation of a US nuclear umbrella for defence against nuclear threats to national territory.Former senior Australian Defence Department official Hugh White, one of the lead authors of the 1993 Strategic Review, has recalled that the inclusion of explicit reference to the nuclear umbrella was discussed only informally with Pentagon officials who indicated 'they would get back to us if they had a problem' (Quoted in O'Neil 2013, 113).
Thus, in the absence of a red light from Washington, Australia chose to incorporate the sole purpose formula of extended nuclear deterrence in its strategic guidance.The 1994 Defence White Paper provided a detailed rationale for Australia's adoption of sole purpose, and is worth quoting at length: The end of the Cold War has reduced the danger of global nuclear war, and concern that US-Australian Joint Defence Facilities in Australia might have become nuclear targets in a global war has receded.Nevertheless, the use of nuclear weapons remains possible, especially if they continue to proliferate.Australia, therefore, will actively pursue multilateral efforts to restrict the proliferation of nuclear weapons.The Government does not accept nuclear deterrence as a permanent condition.It is an interim measure until a total ban on nuclear weapons, accompanied by substantial verification provisions, can be achieved.In this interim period, although it is hard to envisage the circumstances in which Australia could be threatened by nuclear weapons, we cannot rule out that possibility.We will continue to rely on the extended deterrence of the US nuclear capability to deter any nuclear threat or attack on Australia.Consequently, we will continue to support the maintenance by the United States of a nuclear capability adequate to ensure that it can deter nuclear threats against allies like Australia.(Department of Defence 1994, 96) Sole purpose has been reaffirmed in Australian strategic guidance documents since the mid 1990s, and no US administration has endorsed publicly Australia's unilateral position on extended nuclear deterrence, a unique situation among US allies.This has led some to claim that the existence of a nuclear umbrella is more imagined than real, and that Australia cannot assume that extended nuclear deterrence would be activated for its defence in any crisis (Tanter 2009).The claims of critics tend to mirror similar assertions that the ANZUS treaty does not require the US to do anything to defend Australia's security.
Yet, these claims lack credibility for three main reasons.The first is that just as Washington has not spelt out the circumstances in which it would intervene to defend Australia under ANZUS, the absence of an explicit confirmation of the nuclear umbrella does not, ipso facto, render its existence open to question.Australian governments have appeared comfortable with this arrangement; as the Hawke government's formal review of ANZUS in 1983 noted, 'the imprecision of the [treaty] provisions provides deterrent benefit in regard to possible adversaries with respect to uncertainty as to the basis and extend of US military support'. 2Most recently, Australia was named in the 2022 Nuclear Posture Review alongside Japan and South Korea as allies with which the US is engaged to reinforce 'strong and credible nuclear deterrence in the Indo-Pacific' (US Department of Defense 2022, 15).
Second, there has been no operational imperative for Australia to be named publicly by US officials as being under the nuclear umbrella.This contrasts with Japan and South Korea who have both requested formal public commitments by the US during periods of heightened tension with North Korea, while NATO's nuclear sharing arrangements, by definition, involve extended nuclear deterrence commitments.Even in these instances, however, US allies have still historically expressed concern about Washington's willingness to risk the nuclear destruction of US population centres as a by-product of fulfilling extended deterrence commitments (Fruḧling and O'Neil 2021).
Third, the proposition that any US administration would not intervene to defend a formal treaty ally, including countering nuclear threats with a matching response, is problematic for a variety of reasons, not least because of the lasting adverse impact nonintervention would have for America's global reputation.America's allies can take some heart from US support for Ukraine.As Stephen Brooks and William Wohlforth (2023, 86) write: Given how the United States has reacted when Russia attacked a country that is not a US ally -funnelling arms, aid, and intelligence to the Ukrainians and imposing stiff sanctions-the Kremlin surely knows that the Americans would do much more to protect an actual ally.
At the very least, it is hard to see that the absence of explicit statements to this effect would signal any significant difference in US approaches to Australia in such a situation than it would take in case of other allies.

The changing landscape of the Australia-US alliance
Since 2001, the Australia-US alliance has been characterised by attempts to promote greater institutional depth in cooperation.This included the 2011 Force Posture Initiative that built on the intimate intelligence relationship between the two countries-the 'strategic essence' of the alliance (Ball 2001)-as well as close military-to-military cooperation, both in hardware development through joint projects and the exchange of personnel including a record number of Australian Defence Force officers embedded in US combatant commands, most notably INDOPACOM (Hardy 2021).These initiatives have taken place in the context of the growing multilateralisation of US-led security initiatives involving US allies and security partners in the Indo-Pacific designed to contain China's growing influence and assertiveness in relation to territorial disputes (The White House 2022, 12-13).They have included India, Indonesia, the Philippines, and Vietnam, and have built on trilateral arrangements established as far back as the 1990s with Japan, South Korea and Australia, as well as the Quadrilateral Security Dialogue.Australia has been a strong supporter of these arrangements, in no small part because of its desire to lock in a long-term US commitment to the region.
One of the key challenges in substantiating the nuclear umbrella in the Australia-US alliance is that Australia remains the only major US ally that does not have a dedicated extended deterrence consultation process with Washington.This has had more to do with a lack of demand, even resistance, on the Australian side than an unwillingness on the part of the US (Townsend, Santoro, and Warden 2023).Yet, in 2019 the Strategic Policy Dialogue (SPD) was established 'as a forum for Australia and the United States to deepen collaboration to address growing strategic challenges, including on deterrence, arms control, and non-proliferation in the Indo-Pacific region' (Department of State 2022).The creation of this dialogue occurred during a period when the nature of US-Australia strategic cooperation was starting to undergo notable change.The creation of the SPD, which includes senior officials drawn from the Pentagon/Defence and the State Department/Department of Foreign Affairs and Trade, complemented other initiatives that emerged around the same time designed to bolster institutional depth in the alliance.The most notable is the US-Australia Defence Policy and Strategy Talks (DPST).Involving Defence and Pentagon officials, the DPST is described as 'the premier defense policy dialogue for the US-Australia Alliance to address shared challenges in the Indo-Pacific region and beyond by ensuring close coordination and promoting the alignment of strategic guidance' (US Department of Defense 2023a).In spite of this, in 2019 the AUSMIN communique did not even mention deterrence.Nor did it reference new developments on force posture cooperation (Department of Defence 2019).
In 2020, Canberra and Washington agreed to a classified 'Statement of Principles on Alliance Defense Cooperation and Force Posture Priorities in the Indo-Pacific' (Department of Defence 2020a).This established a bilateral Force Posture Working Group to develop recommendations that aimed to 'deter coercive acts and the use of force'.This emerged the same time as Australia began emphasising in its strategic guidance the need for enhanced deterrence through the acquisition of sovereign capabilities to promote long-range strike options against targets in the Indo-Pacific (Department of Defence 2020b).As one author has noted, although the 2023 DSR foregrounded deterrence in an unprecedented way in Australian strategic policy, it was the 2020 Defence Strategic Update that signalled a new desire to marry future capability plans with the imperative of pro-actively deterring adversaries well beyond Australian territory: 'Ideas of denial rather than offsetting-that is, preventing loss rather than imposing demands -began to take over' (Carr 2023, 81).
Central to the aim of deterring potential adversaries well beyond Australian territory was the AUKUS agreement announced in 2021.Substantiated in subsequent implementation plans, including the Optimal Pathway Announcement in 2023, AUKUS is a landmark step in the Australia-US alliance.Pillar 1 is designed to deliver a fleet of conventionally-armed nuclear-powered attack submarines for Australia, but often overlooked is Pillar 2 that promises unprecedented access to key aspects of the US military-industrial base to enhance capabilities for Australia (and the UK) in areas as diverse as artificial intelligence and autonomy, quantum technologies, hypersonic and counterhypersonic capabilities, and electronic warfare (Parish and Nicastro 2023).The unifying theme of AUKUS is that it will enhance deterrence by demonstrating political alignment and building capabilities designed to counter major advances in China's military power in the Indo-Pacific, including a growing numerical superiority and technical proficiency.
AUKUS has both exemplified and catalysed a revised mindset in Australia's approach to the alliance, one that emphasises scaling up operational level cooperation with the US.At the same time, the Albanese government has been careful to emphasise that AUKUS 'is a decision anchored in our own national sovereignty[…]that offers Australia a new level of deterrence and a new capacity to contribute to the stability of our region and the security of our partners' (Albanese 2023).An initial practical sign of increased operational cooperation with the US were Australian-led contracts for infrastructure to host tanker aircraft at the Tindal air base south of Darwin, as well as US investment in military fuel storage in the port of Darwin (Blenkin 2022).In 2021, in the shadow of the AUKUS announcement, Australia and the US agreed to create 'a combined logistics, sustainment, and maintenance enterprise to support high-end warfighting and combined military operations in the Indo-Pacific' (DFAT 2021).By 2022, this had led to agreement to expand the Australian air base at Tindal to enable the hosting of B-52 bombers, and both countries announced plans for further joint enhancement of Australian bases, fuel, and ordnance storage sites to enable operations by US forces (Newdick 2022).This approach to enhanced force posture is consistent with moves by other US alliance partners over the same period to enhance regional security and stability.The Japan-US 2 + 2 meeting in January 2023 provided for 'a vision of a modernized Alliance postured to prevail in a new era of strategic competition' that includes 'an upgrade to US forward presence in Japan including positioning more versatile, resilient, and mobile forces with increased intelligence, surveillance, and reconnaissance, anti-ship, and transportation capabilities' (US Department of Defense 2023c).In February 2023, the Philippines-US alliance announced a revival of the 2014 'Enhanced Defense Cooperation Arrangement'.In April it was confirmed that this would include four new sites (on top of the existing five) at Naval Base Camilo Osias in Santa Ana, Cagayan; Camp Melchor Dela Cruz in Gamu, Isabela; Balabac Island in Palawan; and Lal-lo Airport in Cagayan (Poling 2023).
In early 2023 it was announced that as part of AUKUS, the US would establish a 'Submarine Rotational Force West' of up to four Virginia class submarines in Perth from 2027 (ASA 2023).The 2023 AUSMIN continued the rapid pace of operational expansion of the bilateral partnership.Key additional force posture initiatives were delivered in the air land, maritime, cyber and space domains.The 2023 AUSMIN was heavily orientated towards delivering key initiatives embedded in the DSR, the classified version of which was handed to the Albanese Government in February (Kuper 2023).These included regular rotations of US Army watercraft to Australia, scoping of upgrades to RAAF Bases Curtin and Scherger, the establishment of a flexible guided weapons production and maintenance capability, the announcement of production of Guided Multiple Launch Rocket Systems by 2025, and the maintenance, repair, overhaul, and upgrade of Mk-48 torpedoes and SM-2 missiles in Australia (Corbin and Nason 2023).
Rapidly intensifying cooperation under the Force Posture Initiative since 2019 has increased the salience of conventional extended deterrence in the Australia-US alliance.According to recent polling, a clear majority of Australians are in favour of the United States basing military forces in Australia (Lowy 2023).For the time being, however, the US military presence in Australia is only on 'a rotational basis, as mutually determined, and at the invitation of Australia, with full respect and observance of both Australian and U.S. sovereignty' (DFAT 2023).

Nuclear weapons cooperation as a deterrence maker
Sabre rattling by nuclear-armed adversaries of the US and its allies is nothing new, but in recent times this has increased in frequency.Russia's thinly veiled nuclear threats against Ukraine and NATO, North Korea's explicit nuclear threats against South Korea and Japan, and China's nuclear build-up and coercive behaviour in relation to Taiwan have underscored the continuing importance of the nuclear umbrella in the eyes of US allies.In the Indo-Pacific, unlike NATO, US extended nuclear deterrence is not based on forward-deployed US nuclear weapons, and America's allies historically have had no role in the messaging, force posture, and exercises in relation to nuclear missions.This is changing, however, with Japan and South Korea engaging in greater structured interaction with Washington on extended nuclear deterrence.In the medium to longer term, this has potential momentum to result in a shift to more NATO-like arrangements in the Indo-Pacific whereby 'being implicated in the formulation and signalling of nuclear deterrence also implies embracing responsibility and helping to share the burden of risk' (Mattelaer 2021, 130).
These developments indicate that Australia may soon come under pressure to align its approach to the nuclear umbrella more closely with Japan and South Korea.Tokyo and Seoul have welcomed, and in many cases lobbied in favour of, arrangements that embrace structured consultation and cooperation in areas as diverse as tabletop exercises, inspections of US nuclear delivery platforms and, in the case of the 2023 US-ROK Washington Declaration, future support to US nuclear operations (The White House 2023; US Department of Defense 2023b).US officials have expressed privately a preference that Indo-Pacific allies consider more uniform approaches to managing extended nuclear deterrence that aligns with the strategy of integrated deterrence-to wit, more robust coordination between US inter-agency efforts to bolster deterrence and regional alliance cooperation in multilateral settings (Vergun 2022).This has been overlaid by the Biden administration's continuation of the Trump administration's emphasis on greater alliance burdensharing and growing expectation that US allies will take a lead in their respective sub-regions (Wallis and Powles 2021).
While Washington and Canberra (in particular) have been careful to sidestep the nuclear dimension of the alliance, attempts to quarantine this from conventional military cooperation are becoming increasingly strained.To be sure, conventional deterrence and nuclear deterrence exist on the same spectrum, though it is also the case that they are qualitatively different in practice.As James Wirtz points out, 'the contestability of conventional threats can raise doubts in the minds of those targeted by conventional deterrence concerning the capability of the side issuing deterrent threats to actually succeed […]by contrast, deterrent threats based on nuclear weapons are largely uncontestable' (Wirtz 2018, 58).
The deeper operational military cooperation that has become a feature of the Australia-US alliance since 2019 has opened a window of opportunity for Australia to bolster its contribution to the nuclear umbrella.Doing so would promote strategic guidance that has existed since the 1990s affirming extended nuclear deterrence as a key element of the US security guarantee under the alliance.The need to factor in the prospect of nuclear coercion against Australia in a regional crisis-in many respects the underlying rationale of extended nuclear deterrence-is more compelling today than it has been in the past.North Korea has acquired an intercontinental nuclear strike capability that can reach any location in Australia, and Pyongyang has a history of issuing explicit threats against Australian territory (Greene 2017).For its part, China's rapid nuclear modernisation appears aimed at providing Beijing with a wider range of targeting options in the Indo-Pacific, with new ICBM silo development deep inside China rendering these silos 'less vulnerable to long-range conventional strikes' (Kristensen and Korda 2023, 289).
More generally, bolstering Australia's contribution to extended nuclear deterrence would also serve to widen the footprint of the US nuclear umbrella in the Indo-Pacific, further offsetting the risks of nuclear proliferation among US allies Japan and South Korea, both of which remain capable of acquiring nuclear weapons and have a shared historical interest in exploring technical pathways to a threshold capability (Romei 2023).This would accord with Australia's long-established emphasis on reinforcing nuclear non-proliferation globally.
There is another specific reason why it is in Canberra's short-term interest to strengthen Australia's contribution to the nuclear umbrella.This relates to the potential for a second Trump presidency from 2025 and the return of a more acute focus in Washington on what US allies are doing to earn their security guarantees.This was a major theme of the first Trump administration, and it is possible that a second Trump presidency would be even more radical in its approach to alliance management.Australia should not make the mistake of thinking that it is somehow immune from this and that AUKUS could not be stalled or even wound back by a new administration.By demonstrating that it is prepared to make tangible contributions across the spectrum of US security guarantees, Australia would be better able to vindicate claims that it is fully committed to supporting the US as an alliance partner.
What steps, then, can Australia take to increase its contribution to extended nuclear deterrence?The first major step should be to propose to the US a dedicated extended deterrence dialogue involving deliberations about nuclear strategy along the lines of the US-Japan and US-ROK examples.Extended deterrence dialogue between the US and Japan and the US and South Korea has existed for one and a half decades, and each arrangement has its own unique characteristics.For instance, due to the highly operationalised nature of the US-ROK alliance underpinned by Combined Forces Command, the extended deterrence dialogue includes significant discussion and planning of the respective roles of both sides in any contingency relating to North Korea.As one South Korean observer has commented, the new US-ROK Nuclear Consultative Group 'has a system comparable to NATO's Nuclear Planning Group' and 'is the first permanent nuclear-related consultative body of its kind that the US did not even allow for Japan' (Chung 2023).Any proposed extended deterrence dialogue involving the US and Australia should align closely with formal institutions of the alliance and be constituted as a subcommittee of an expanded Strategic Policy Dialogue involving agencies from across the national security bureaucracy.In addition to proposing a bilateral extended deterrence dialogue with Washington, Canberra should be receptive to a potential multilateral nuclear planning forum among US Indo-Pacific allies of the type proposed in the 2021 Chicago Council on Global Affairs report, whose authors included former US Secretary of Defense Chuck Hegel, and former Australian Prime Minister and current Ambassador to the United States Kevin Rudd (Daalder et al. 2021).Such an arrangement would complement existing multilateral security initiatives in the Indo-Pacific in which Australia is involved.
The second step should be to ensure that any bilateral dialogue on extended deterrence encompasses discussion of delicate questions concerning crisis escalation scenarios and mutual expectations.Constructing scenarios of how Australia would support US operations at different levels in different contingencies will be central to this.As Kelsey Hartigan (2023) has noted, a focus is required on what each side perceives as escalatory (including how they perceive Chinese red lines), who would do what during a crisis, how each side would communicate with one another and the public during a contingency, and whether and how the alliance would integrate conventional and nuclear operations during a crisis.
An aversion to being locked into future US nuclear operations against China-and associated concerns over Beijing's reaction-will be a political obstacle for Australia engaging in such a dialogue.Indeed, this apprehension is the likely reason why Australian officials remained unresponsive to US suggestions before 2019 for a bilateral strategic dialogue outside of the 2 + 2 AUSMIN.Anxiety over possible entrapment resulting from pre-commitments cannot be dismissed and is an inescapable feature of smaller allies' calculations in dealing with their major power ally.The flip side, however, is that dialogue around crisis escalation scenarios can only help avert a future situation where one side feels the other has not delivered fully on its commitments in the moment of truth.As one author observes, 'closer integration could ultimately help to stabilise both parties' roles and expectations' (Carr 2023, 89).
Third, Australia needs to remain receptive to any future proposals to forward base US nuclear capable platforms and be ready to support US nuclear operations in a future war in the region.This will be a jarring recommendation for some who will point to what they see as probable regional disquiet triggered by such a move.However, Australia's neighbours are likely to have nuanced views about US nuclear-capable platforms being stationed in the region.Pacific Island states (and possibly New Zealand) would likely be the most vocal in pushing back publicly but given growing tensions with China on maritime territorial disputes, ASEAN states are far from united on the question of a more sustained US nuclear-capable presence in the region.Indeed, in July 2023, the two B-52 aircraft quietly concluded a joint interoperability exercise with the Indonesian air force; this exercise involved these US platforms operating from Indonesian territory (US Air Force 2023).Ultimately such a move is completely aligned with Australia's declared regional balancing strategy and growing focus on deterrence aimed at maintaining regional order and the status quo (Freedman 2008, 4).
Overall, Australian governments need to be more open about hosting US nuclear capable platforms and place this firmly in the context of delivering on Australia's alliance responsibilities as distinct from a legalistic discourse around ANZUS treaty obligations.This should be analogous to the approach taken with the Joint Facilities, which have been portrayed as contributing directly to nuclear deterrence.As the Japanese and South Korean examples demonstrate, extended nuclear deterrence is no longer about being a passive recipient of assurances-the credibility of the nuclear umbrella is shaped increasingly by operational level commitments on the part of junior allies.
Attention needs to focus more directly on Australia participating in exercises geared to conventional support to nuclear operations of the type undertaken by NATO allies and endorsed in the US-ROK Washington Declaration.Such exercises should be portrayed as part and parcel of Australia's alliance commitments, not something to be avoided because of the perceived risk of domestic political blowback or condemnation by Beijing.Taken together, these initiatives would help to address a fundamental question for those who advocate benefitting from US extended nuclear deterrence but are unwilling to support in a material way the capabilities that underpin this assurance.As one observer of allied nuclear cooperation notes, 'can one ask one's ally to do what one is not, as a matter of principle, willing to do for oneself?' (Mattelaer 2021, 131).
Finally, Australia should revert to its previous stance of opposing the annual UN General Assembly resolution endorsing the Treaty on the Prohibition of Nuclear Weapons (TPNW).Concluded in 2017 and entering into force in 2021, the TPNW prohibits signatories from participating in any nuclear weapons activities, including 'the deployment of nuclear weapons on national territory and the provision of assistance to any State in the conduct of prohibited activities' (UNODA 2023).A resolution in support of the TPNW is tabled annually at the UN General Assembly and is the product of close cooperation between Treaty parties and the International Campaign Against Nuclear Weapons (ICAN).Australia has not signed the Treaty and from 2017 to 2021 Australian governments had argued, correctly, that the TPNW was incompatible with Australia's commitments under its alliance with the US (Galloway 2021).Yet, in 2022, the Albanese government abstained on the annual resolution, overturning the previous government's opposition.The abstention reflected the Labor government's sympathy for the Treaty; in Opposition, Anthony Albanese had personally sponsored his party's initial endorsement of the TPNW at the Labor Party's 2018 national conference and support for signing and ratifying the TPNW was reaffirmed at the 2023 national conference (ALP 2023, 100-101).Foreign Minister Penny Wong has reaffirmed that the Albanese government is 'systematically and methodically' weighing whether to sign the TPNW (Stewart 2023).Canberra's abstention on the 2022 UN General Assembly resolution elicited a statement from the US that any decision by Australia to join the TPNW 'would not allow for US extended deterrence' (Hurst 2022).
Despite claims that Australia's abstention on the TPNW represents a welcome demonstration of 'sovereignty' when it comes to the alliance (ICAN 2023), from a policy perspective Australia's revised position is inherently contradictory-projecting ambivalence about the role of nuclear weapons in international forums while simultaneously invoking US nuclear protection in national strategic guidance.It is also conspicuously out of step with the position of other US treaty allies.NATO's formal position is that the TPNW 'is inconsistent with the Alliance's collective defence commitments' (NATO 2023) while Japan and South Korea have voted consistently against the Ban Treaty in UN forums, including at the UN General Assembly (NWBM 2023).
Endorsing a treaty that treats all nuclear weapons possession as a uniform threat to international security overlooks the distinction between a nuclear-armed US, which is an ally of Australia, and other nuclear weapon states, including China which is persistently opaque about its own nuclear force modernisation, and Russia and North Korea which engage regularly in nuclear sabre rattling for coercive purposes.More importantly, for as long as it claims the applicability of the nuclear umbrella and recognises that the latter plays an important role in non-proliferation among America's allies, Australia should actively support US extended nuclear deterrence.This is part of alliance burden-sharing.

Conclusion
Just as the Australia-US alliance has acquired greater depth over the past twenty years due to contingent factors rather than the ANZUS treaty per se, so too the nuclear umbrella must evolve in future as a result of initiatives outside the scope of formal treaty commitments.We have argued that the changes currently underway in the Australia-US alliance present an unprecedented opportunity for Australia to reimagine its contribution to extended nuclear deterrence.This will require strong leadership due to a general ambivalence about nuclear weapons in Australia and a popular view-reinforced by AUKUSthat Australia is a consumer of alliance benefits rather than a provider.As noted, the future of the US alliance cannot be taken for granted despite the major advances in operational military cooperation since 2019.The US political system is unpredictable, fluid, and dynamic and it would be a mistake to assume that long-standing US international commitments will necessarily remain immune from this.
While alliance related commitments by major powers are hard to disavow down the track, it is possible.One only need contemplate a second Trump administration to appreciate that US alliance commitments, including subsidiary agreements, might change over time without formal treaties being renegotiated.Given the centrality of the nuclear umbrella in Australian strategic guidance, it is important that governments put measures in place to ensure that Australia is an active contributor to extended nuclear deterrence rather than a passive recipient, as is the case today.As a junior alliance partner, the temptation is always there to be a security-taker rather than a securitymaker.This may even be what large sections of the Australian community preferlower taxes and keeping out of harm's way are usually preferable to the alternatives.However, the long-term sustainability of Australia's alliance with the US will depend on the extent to which Canberra is willing to share risks and contribute support to core US military capabilities, which includes the potential to undertake nuclear operations against adversaries.As a first step, this requires acknowledging the responsibilities, as well as the benefits, that flow from the US nuclear umbrella.

Notes
1.As well as, in relation to nuclear deployments, Australia's commitments under the Rarotonga Treaty.