Why It Matters
The loss of New START erodes confidence in US nuclear guarantees to Europe and signals a broader erosion of arms‑control architecture, heightening strategic uncertainty across the trans‑Atlantic alliance.
Key Takeaways
- •New START expired, ending last US‑Russia strategic arms treaty
- •US‑Russia limits may persist via informal “handshake” agreement
- •Treaty did not constrain theater nuclear forces threatening Europe
- •Russian modernization targets US missile defenses, raising escalation risk
- •China’s expanding arsenal hampers future multilateral arms‑control efforts
Pulse Analysis
The expiration of New START marks a watershed moment in post‑Cold‑War arms control. For decades, the treaty provided a transparent framework that limited the size of the US and Russian strategic arsenals and facilitated data exchanges, on‑site inspections, and confidence‑building measures. Its disappearance removes a rare channel of dialogue between the two nuclear powers, forcing policymakers to rely on ad‑hoc arrangements that lack verification rigor. In an environment where both sides are pursuing costly modernization programs, the absence of a formal cap could accelerate an unchecked buildup, complicating crisis management and increasing the risk of miscalculation.
Europe feels the reverberations most acutely. While New START did not regulate theatre‑level nuclear weapons—systems that Russia can deploy against NATO members—the treaty underpinned the broader credibility of US extended deterrence. Without a binding framework, European leaders confront growing doubts about Washington’s ability to limit escalation and protect allies from limited nuclear use. This uncertainty fuels debates in several European capitals about developing indigenous nuclear capabilities, a shift that could further destabilize the regional security architecture and provoke Russian countermeasures.
The strategic landscape is now truly triangular, with China’s rapidly expanding nuclear force adding a new dimension to deterrence calculations. Both Moscow and Washington must factor a third nuclear actor into their force‑posture decisions, making bilateral arms‑control solutions increasingly untenable. Future agreements will likely need to incorporate China and perhaps NATO nuclear states to remain viable, but political will remains scarce. Europe’s pragmatic path may involve bolstering conventional strike capacities, deepening missile‑defence cooperation, and investing in resilient command‑and‑control systems to preserve deterrence credibility amid an evolving, multilateral nuclear environment.
New START Expiry: Implications for Europe
The expiry of New START could further undermine the credibility of US extended deterrence and complicate European and US efforts to strengthen conventional deterrence.
Today, 5 February 2026 – the last US‑Russian arms‑control agreement, the New Strategic Arms Reduction Treaty (New START), expired. Concluded in 2010, the treaty placed quantitative limits on warheads deployed on US and Russian strategic delivery systems (ICBMs, SLBMs and heavy bombers), as well as on the numbers of deployed and non‑deployed strategic launchers. New START also provided for extensive reporting, verification and risk‑reduction measures to support the treaty’s effective implementation. New START was the last remaining piece of arms‑control infrastructure between Russia and the US; Washington withdrew from the Anti‑Ballistic Missile (ABM) Treaty in 2002 and the Intermediate Nuclear Forces (INF) Treaty in 2019 (citing Russian violations), with Moscow withdrawing from the Conventional Armed Forces in Europe (CFE) Treaty in 2023.
Russia suspended its ratification of New START in 2023; today the treaty officially expired. At the last minute, reports emerged that the US and Russia were nearing an agreement to extend the terms of the treaty for a limited amount of time. At the time of drafting, the details of the reported agreement (for instance, whether it would include compliance with quantitative limits only or also see the resumption of data exchanges and inspections), or the likelihood that it would be concluded at all, were not clear. As one US official is reported to have noted, any continued compliance with New START limits would have to rely on a ‘handshake’ deal, seeing as the treaty does not allow for further formal extensions. Regardless, this comes as a welcome development in a strategic environment in which both Moscow and Washington have incentive to expand their strategic capabilities.
However, should the New START limits on US and Russian strategic forces indeed collapse, the direct impacts of New START for Europe are likely to be limited – at least in the short term. The treaty did not address the systems of most direct concern to Europe – namely, theatre nuclear forces – and neither Russia nor the US is in a position to begin a major nuclear buildup. What is of greater importance than the end of the treaty itself are the strategic conditions that accompany its expiry, which persist and will determine key features of Europe’s security environment.
Doomed from the Start
The completion of New START – and the arms‑control architecture established between Moscow and Washington over the course of the Cold War and in the years that followed its conclusion – was an impressive achievement in more ways than one. The agreement ran counter to both US extended deterrence and Russian incentives to hedge against a perceived first‑strike risk. The frameworks thus defied strategic gravity for longer than might have been expected.
“All institutions and procedures – including arms control agreements – rest on political and material foundations that lie well beyond their formal remit.”
A key consideration here is the demands on US forces created by US extended‑deterrence commitments, with the US being perennially challenged to prove it would trade ‘Washington for Bonn’. During the Cold War and into the post‑Cold‑War period, US advantages in intelligence, surveillance and reconnaissance (ISR), missile accuracy and the ability to track SSBNs helped mitigate these fears by sustaining the prospect of damage limitation. In principle, the United States could credibly threaten Russian strategic forces while retaining sufficient survivable capability for follow‑on strikes. Escalation on behalf of European allies, in other words, did not automatically entail the certainty of national annihilation. It was never a given such damage limitation would succeed, considering the sheer scale of the Soviet – and later Russian – arsenal. Yet, by reducing the inevitability of catastrophic retaliation through the maintenance of a large strategic nuclear arsenal, the United States made extended deterrence more credible than it would otherwise have been.
Nevertheless, this logic always carried an inherent tension: the same capabilities that enable damage limitation can also be perceived as elements of a first‑strike posture, a point well understood in both Moscow and Washington. Figures involved in Cold‑War negotiations understood that what the US defined as parity and a balance necessary to make its commitments credible, the Soviets would see as US superiority. This inherent asymmetry makes arms control implacably difficult. When arms‑control agreements did occur in the past, they often did so against the backdrop of a wider lessening of tensions (for example the era of détente) which reduced the salience of the finer points of the nuclear balance in policymakers’ eyes. However, the shaky foundations on which agreements rest have meant their de‑facto or de‑jure abrogation has always been more likely than not in periods when tensions inevitably resurfaced.
For contemporary Russia, this tension has been compounded by two developments which drive Russian thinking on its strategic balance with the US.
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US conventional prompt‑strike capabilities capable of engaging elements of Russia’s nuclear forces that previously could only be targeted with nuclear weapons. This expands the set of systems Russia must consider when assessing threats to its deterrent.
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Improved US missile defences, which could provide a degree of homeland protection sufficient either to blunt a calibrated Russian response to a largely conventional first strike, or to intercept residual forces after multiple waves of attack. Russia’s development of systems such as the RS‑28 Sarmat – capable of carrying up to fifteen MIRVs, compared with the ten carried by the R‑36 it replaced – reflects an intent to preserve the ability to rapidly exceed New START limits on deployed warheads if required. Russian officials, including then Deputy Defence Minister Yuri Borisov, explicitly framed Sarmat’s heavy payload as a response to US missile defence. In parallel, Russia has pursued novel systems such as the nuclear‑powered Poseidon torpedo and the Burevestnik cruise missile, which lie entirely outside the treaty framework.
The structural difficulty of sustaining New START’s limits has since been compounded by a further factor: the rise of China as a conventional – and increasingly nuclear – peer of the United States. Beijing has expanded its nuclear arsenal at breakneck pace over the last few years; US intelligence expects China to have an arsenal of roughly 1 500 warheads by 2035. This necessarily impacts US assessments of how big – and what kind – of a nuclear force is enough to deter not one but two adversaries, while also providing for the maintenance of a credible extended‑deterrence posture. Steps the US takes to rectify perceived imbalances vis‑à‑vis Russia and China, taken collectively, will look to each party like the US widening a lead it enjoys, in bilateral terms, over the concerned state. This concern was articulated recently by Admiral Igor Kostyukov, Deputy Director of the GRU, who argued that the deployment of US missiles in East Asia constituted a threat to Russia’s Strategic Missile Forces.
A dynamic that was already unstable in a dyadic setting thus becomes untenable in a triangular relationship: the United States is compelled to reason about deterrence in collective terms, while each adversary continues to judge US capabilities solely against its own bilateral balance.
The Question for Europe
The expiry of New START limits could – in theory – allow for the expansion of US strategic forces to address the two‑peer deterrence challenge. However, any progress on this front will take time to materialise, if it does at all. The total (deployed and undeployed) numbers of strategic launchers in the Russian and US arsenals are currently within New START limits. Furthermore, the US and Russia are both already undertaking costly modernisation programmes to upgrade their existing strategic capabilities. Both programmes have been plagued by issues. On the American side the Sentinel ICBM has faced an 81 percent cost overrun, while Russia’s RS‑28 Sarmat ICBM has seen high‑profile test failures. As such, any significant expansion of strategic systems in the short term is unlikely. A more feasible option may be the uploading of additional warheads onto existing strategic systems. Furthermore, if a more permanent and formal extension of quantitative limits on strategic forces is not reached eventually, this period of limbo – depending on how long it lasts – may allow the two sides to position themselves to expand their arsenals at shorter notice if and when the restrictions finally collapse.
More to the point, because New START governed the strategic balance between Russia and the United States, it did little to constrain the Russian capabilities most immediately threatening to Europe – namely, non‑strategic nuclear weapons. Russia maintains a significant quantitative and qualitative (in terms of diversity of systems) advantage. The UK and France do not possess non‑strategic nuclear capabilities and have therefore historically relied on the credibility of US extended deterrence to deter limited Russian nuclear use in Europe. The implications of New START collapse for the credibility of US damage‑limitation capabilities therefore threaten to exacerbate anxieties in Europe over the credibility of US extended deterrence. Public debate in parts of Europe and Canada over the need to develop national nuclear deterrents has shown how that credibility has already degraded among allies in the face of apparent US disengagement from – and outright undermining of – European security.
Furthermore, it raises the possibility that US efforts to manage this challenge are interpreted by Russia as a drive towards nuclear primacy. In such an environment, capabilities that might appear marginal in isolation can assume outsized significance, because Russia cannot rule out their employment in concert with US forces. Seen through this lens, senior Russian leaders’ public concern over Japan’s acquisition of 400 Tomahawk land‑attack missiles – despite the limited number of missiles and their clear orientation toward China – becomes more intelligible.
The lesson for Europe is that even limited investments in conventional strike capabilities by US allies can exacerbate Russian perceptions of vulnerability if these missiles are viewed as part of an aggregate imbalance, while further entangling the United States in European deterrence for the same reasons.
Conclusions
The demise of New START is emblematic of Henry Kissinger’s observation about how a certain technically oriented style of diplomacy often assumes the correct procedures can shape strategic outcomes. In reality, all institutions and procedures – including arms‑control agreements – rest on political and material foundations that lie well beyond their formal remit. New START was grounded in a set of conditions that were inherently fragile: a brief period of relatively cooperative US‑Russian relations; a temporarily stable nuclear balance between two states otherwise unequal across most dimensions of power; and an increasingly artificial assumption of a purely dyadic nuclear order in a world where conventional capabilities can directly affect the nuclear balance. The collapse of the treaty should therefore come as no surprise. Should the treaty limits be extended, Russia and the US will still have a long road ahead of them to make sure that the restrictions can be sustained in the face of countervailing strategic winds.
Any future arms‑control initiatives will bring to the table a slew of new challenges to manage. Considering China’s quickly expanding arsenal, it is difficult to conceive of a sustainable arms‑control arrangement that does not account for the impact of China’s forces on the strategic environment. At the same time, Moscow has long been calling for France and the UK to be included in arms‑control efforts. Yet, both states maintain a minimal credible deterrent posture; as such, quantitative reductions in UK and French nuclear arsenals will remain a non‑starter in the current strategic environment and until Russia – and by extension, the US – are ready to reduce their own arsenals.
The prospects for future arms control thus remain dim. Europe will need to consider not the question of how to restore a lost stability, but rather how to secure a position of relative security in a context that will be, by its very structure, inherently unstable.
Authors
Darya Dolzikova – Senior Research Fellow, Proliferation and Nuclear Policy (RUSI)
Dr Sidharth Kaushal – Senior Research Fellow, Sea Power, Military Sciences (RUSI)
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