Nuclear, explained.
A poster in Washington DC last month warning about the impending expiration of the New START treaty (Probal Rashid/LightRocket via Getty Images)
Without US-Russian limits on nuclear arsenals, Australia faces a more dangerous Indo-Pacific with fewer guardrails.
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New START expired. Now what for global nuclear stability?New START expired. Now what for global nuclear stability?
On 5 February, the New Strategic Arms Reduction Treaty (New START) expired, bringing to an end the last remaining legally binding agreement limiting the strategic nuclear arsenals of the United States and the Russian Federation. For the first time since 1972, the world’s two largest nuclear powers will no longer be constrained by any formal framework governing the size, deployment, or verification of their strategic nuclear forces.
Both states retain the technical capacity to rapidly expand deployed arsenals by uploading additional warheads onto existing delivery systems. While neither has yet announced a full-scale numerical expansion, the absence of limits lowers the political and strategic barriers to doing so.
The loss of transparency is the most immediate consequence of the expiration of the treaty. Verification regimes allowed each side to distinguish between routine activities and destabilising preparations. Without them, intelligence assessments rely increasingly on indirect indicators, encouraging conservative and often pessimistic assumptions about adversary intent. Given the inconsistency in relations between Trump 2.0 and the Kremlin, this dynamic heightens the risk of arms racing driven less by actual threat than by fear of surprise or disadvantage.
The ramifications reach beyond the bilateral US–Russia relationship. China’s ongoing and rapid nuclear expansion is now unfolding with no functioning great power arms control framework. While Beijing’s arsenal remains smaller than those of Washington and Moscow, the absence of constraints and guardrails may reinforce incentives for all three powers to hedge against each other’s future capabilities.
Taken together with the insertion of emerging technologies, the result will spur a more complex, multipolar nuclear order with fewer stabilising mechanisms than existed during the Cold War.
For Australia, the implications are profound. The challenge lies in balancing alliance commitments with advocacy for restraint.
Unsurprisingly, the collapse of bilateral arms control among the major nuclear powers significantly undermines the credibility of the broader nuclear non-proliferation regime. Under the Nuclear Non-Proliferation Treaty (NPT), non-nuclear-weapon states accepted permanent abstention from nuclear weapons in exchange for access to peaceful nuclear technology and a commitment by nuclear-weapon states to pursue disarmament. As has been evident across the last decade, the visible retreat from arms control in this instance only weakens this bargain.
For many non-nuclear states, the expiration of New START reinforces perceptions that nuclear-armed powers are prioritising strategic competition over disarmament obligations. This erosion of trust complicates efforts to strengthen non-proliferation norms and may embolden proliferators or threshold states to question the long-term value of restraint.
Arms control agreements historically have also provided channels for communication and reassurance even when political relations deteriorated. In their absence, crises become more dangerous.
The absence of US–Russian arms control markedly complicates the picture in the Indo-Pacific, and with it, Australia’s strategic environment. Australian security rests in part on extended deterrence provided by the United States, and on the stability of international norms that discourage nuclear proliferation and escalation. Australia has attempted to navigate the tension between supporting US strategic credibility and advocating for nuclear restraint. Australian diplomacy will need to emphasise the importance of deterrence stability rather than sheer numerical superiority.
China’s military modernisation, including its nuclear forces, has also become a central point of concern. Beijing has historically resisted participation in arms control regimes citing disparities in arsenal size, however, the breaking down of existing agreements such as New START will only further reduce incentives for substantive engagement. For Australia, this means operating in a region where nuclear dynamics are less predictable and less constrained.
Australian defence planning has already shifted toward greater emphasis on deterrence by denial, long-range strike, and advanced conventional capabilities. These investments can be understood partly as a hedge against the unpredictability of the nuclear domain and uncertainty in the region. By strengthening conventional deterrence, Australia reduces its exclusive reliance on nuclear umbrellas and contributes to a more layered deterrence posture. This does not necessarily replace extended deterrence but complements it, enhancing stability by raising the threshold for escalation and providing policymakers with a broader range of response options in a crisis.
Australia also faces an opportunity to exercise normative leadership. As a non-nuclear state with strong alliance credentials, Canberra is well positioned to advocate for renewed arms control, risk reduction measures, and confidence-building initiatives. This includes active engagement in NPT processes, support for transparency initiatives, and encouragement of dialogue among nuclear-armed states. Such advocacy should not be viewed as naïve idealism, but an illustration of interest in restoring predictability and reducing the probability of catastrophic outcomes.
In 2009, Barack Obama spoke of a “world without nuclear weapons” and “to end Cold War thinking” – words that sparked significant dialogue and actions all around the world. With the expiration of New START, we now enter a period that marks a critical inflection point in global security. It signals the end of an era in which strategic nuclear competition was at least partially governed by rules, transparency, guardrails and mutual restraint. The resulting environment is characterised by uncertainty, weakened norms, and heightened risk of miscalculation.
For Australia, the implications are profound. The challenge lies in balancing alliance commitments with advocacy for restraint, strengthening national defence capabilities while supporting global non-proliferation, and navigating a regional environment shaped by great power competition. In a world without New START, strategic stability can no longer be taken for granted; it must be actively managed through diplomacy, defence planning, and sustained commitment to the principles that have long underpinned global security.
About the author
Aiden Warren
Professor Aiden Warren is based at the School of Global, Urban and Social Studies at RMIT University in Melbourne and is Theme Leader (National Security) at Centre for Cyber Security Research and Innovation (CCSRI).
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