On the 5th of February 2026, the New Strategic Arms Reduction Treaty (New START) between the United States and Russia is set to expire, removing the last formal constraints on the world’s two largest nuclear arsenals. Its expiry is not merely a strategic event; it is a profound moral turning point. For over a decade, New START provided more than caps on deployed warheads and delivery systems—it created a framework of restraint, transparency, and normative signalling, constraining the existential risks posed by nuclear weapons. With its lapse, the ethical responsibility to avert catastrophe now falls squarely on states and the global community.
Nuclear weapons, by their very nature, are instruments of indiscriminate and potentially apocalyptic harm. Their existence and deployment raise profound moral questions, particularly when assessed through the lens of just war theory (both jus ad bellum and jus in bello): the principles of discrimination, which require combatants to distinguish between legitimate military targets and civilians, and proportionality, which demands that the harm caused by military action not exceed the legitimate military objective. Nuclear arsenals, even if maintained primarily for deterrence, inherently threaten the survival of vast civilian populations, and their use cannot be reconciled with these ethical standards.
The moral stakes extend far beyond the immediate battlefield. They encompass populations that have no role in state decision-making: distant allies, neutral states, and non-nuclear nations may all be affected by miscalculation, accidental escalation or signalling intended to demonstrate resolve. In this sense, the ethical obligations of nuclear states are not confined by geography or borders. As Thomas Nagel emphasises in The Problem of Global Justice, moral responsibility is not limited to compatriots or co-citizens. States have obligations to protect, or at least not to imperil, the lives of individuals globally. Nagel distinguishes between national self-interest and global justice, arguing that actions taken to secure the safety or advantage of one’s own population can generate moral claims of harm or injustice against distant populations. Nuclear policy, by creating the capacity for catastrophic harm to others, directly invokes these claims.
Even ostensibly defensive postures—so-called “deterrent” strategies—carry profound ethical weight. Misjudgements in signalling, incomplete restraint, or failure to implement rigorous safeguards can place millions of lives at risk. Ethical responsibility is forward-looking and universal: it demands anticipation of how decisions made today ripple across borders, influencing the security, health, and survival of others. The existence of nuclear weapons transforms abstract moral concerns into concrete obligations: to maintain maximum transparency, to adhere to verification mechanisms, to minimise the risk of miscalculation, and ultimately, to seek pathways to reduction and disarmament. In a globalised world, no nuclear state can claim that its decisions are morally localised; each action reverberates across the international system, generating ethical duties to prevent catastrophic outcomes, even for populations with whom a state shares no direct political or military tie.
Nagel’s insistence on moral universality, coupled with the existential stakes posed by nuclear arsenals, underscores a fundamental truth: the possession of nuclear weapons is inseparable from moral responsibility, and ethical analysis must guide both policy and strategy. The global risk landscape created by nuclear deterrence is not merely a technical or strategic problem—it is a profoundly moral one. States that fail to account for the consequences of their nuclear posture on distant lives violate the principles of justice and responsibility that Nagel articulates, highlighting the urgency of coordinated, ethically informed approaches to arms control, restraint, and eventual disarmament.
Hobbes, Security, and Visible Proliferation Risks
The expiry of New START intensifies what Thomas Hobbes in Leviathan or The Matter, Forme and Power of a Commonwealth Ecclesiasticall and Civil described as the state of nature: a world of anarchy in which survival is uncertain and actors rely on self-help to secure their own safety. In this framework, the absence of overarching authority produces competition, distrust and pre-emptive military logic: states arm themselves not out of aggression, but because they cannot safely rely on others.
Nuclear weapons amplify this Hobbesian calculus. With arms control gone, states perceive heightened risk from strategic peers, prompting observable proliferation hedges. In Europe, countries such as Poland have signed security agreements with France, while discussions continue around a European Union nuclear deterrent independent of the United States. In East Asia, Japan and South Korea are signalling renewed interest in nuclear-adjacent capabilities amid uncertainty about U.S. extended deterrence. Meanwhile, China’s breakneck nuclear expansion continues unconstrained, and Pakistan’s nuclear arsenal, historically India-focused, is now being extended through a strategic defence pact with Saudi Arabia, potentially incorporating longer-range delivery systems. These developments illustrate a shift toward a post-non-proliferation order: countries are hedging and signalling independently, creating a web of proliferative influence that spans multiple continents.
This environment exemplifies the security dilemma in game theory: defensive measures by one state increase perceived threat for others, prompting reciprocal expansion. The logic of Mutually Assured Destruction (MAD) intensifies this dynamic, as states recognise that any nuclear exchange could be catastrophic for all, yet the threat itself compels continued investment and signalling. Hedging, extended deterrence arrangements, and nuclear-adjacent alliances are not merely strategic; they are ethically charged. Each decision carries potential consequences for populations beyond national borders, illustrating the moral weight inherent in Hobbesian self-help. Even as states pursue ‘rational’ survival strategies under MAD, they generate cascading ethical risks, akin to a global moral hazard.
Necropolitics and the Ethical Stakes of Nuclear Policy
Achille Mbembe’s concept of necropolitics provides another lens. Nuclear weapons institutionalise the power to decide who may live and who may die among millions of people. Each deployment, modernisation programme or signalling exercise enacts a necropolitical claim: certain populations are rendered strategically expendable in the logic of deterrence. In a post–New START world, these necropolitical stakes are heightened, as the erosion of formal treaties intensifies both proliferation and risk.
States cannot disclaim responsibility for risks they enable, even indirectly. Hence nuclear proliferation is never morally neutral. Every decision—from arsenal expansion to extended deterrence arrangements—carries consequences for life and death beyond national borders. Under Mbembe’s lens, to act purely according to rational self-help logic is to neglect the moral accountability owed to populations made vulnerable by strategic competition.
Moral Imperatives and the Case for Renewed Activism
The lapse of New START is also a clarion call for coordinated global ethical action. Hobbesian self-help and the security dilemma explain why states hedge, expand, and signal, but they do not excuse moral inaction.
Drawing once more on Michael Walzer’s principles of just war, nuclear weapons raise profound ethical concerns because they violate the requirements of proportionality and discrimination. Proportionality demands that the harm caused by military action not be excessive in relation to the legitimate aim; nuclear arsenals, by their very nature, threaten catastrophic civilian destruction that far exceeds any conceivable military objective. Discrimination requires combatants to distinguish between legitimate military targets and non-combatants. Even when deployed solely for deterrence, nuclear weapons carry the potential to harm vast numbers of civilians indiscriminately, making their very possession and signalling morally fraught. Survival alone, under this framework, does not justify actions that could foreseeably endanger millions of innocent lives.
Behavioural ethics further illuminates the risks. Human and institutional decision-making is bounded by cognitive biases, risk misperception and overconfidence. Leaders and policymakers operate under high uncertainty, and even well-intentioned strategic choices can produce catastrophic consequences. Misreading signals, underestimating escalation risks or over-relying on the assumed rationality of adversaries can inadvertently bring states closer to nuclear use. Behavioural ethics demonstrates that moral responsibility is not suspended in uncertainty; rather, it is intensified. States must anticipate not only the direct consequences of their choices but also the systemic and global impact of their actions.
A renewed programme of coordinated nuclear disarmament activism is therefore ethically imperative. Such efforts should:
- Reassert moral norms against nuclear expansion, modernisation and testing, embedding ethical responsibility alongside strategic reasoning.
- Mobilise civil society and global coalitions to press states toward phased reductions, verification and transparency, ensuring that survival strategies do not override ethical constraints.
- Promote a shared ethic of restraint, signalling that life, even in distant nations, cannot be treated as an expendable variable in strategic calculations.
- Integrate moral accountability into alliances, ensuring that hedging arrangements or extended deterrence do not obscure ethical responsibility for populations caught in escalation zones.
Ethical activism is inseparable from diplomacy and strategy. Just as New START relied on verification and trust, contemporary nuclear governance requires moral pressure and norm-building. States must be prevailed upon to act with foresight, transparency and accountability.
Conclusion
The expiry of New START is not merely a strategic turning point—it is a moral and ethical watershed. It removes the last legally binding constraint on the world’s two largest nuclear arsenals, creating visible proliferation pressures in Europe, the Middle East, South and East Asia.
Ethics, therefore, must guide the next phase of nuclear policy. Coordinated activism, norm-setting, and disarmament diplomacy are not optional—they are moral imperatives in a world where New START’s absence has removed formal legal restraints. Survival, credibility, and national interest remain important, but they are ethically insufficient in the absence of global accountability. Humanity now faces a test of moral courage: whether it can restrain, reduce, and eventually eliminate nuclear threats while ensuring that strategic rationality does not override the moral responsibility to protect life.
The post–New START world is thus not only anarchic and strategically complex—it is ethically urgent. The question is no longer merely whether states can maintain deterrence; it is whether they will uphold their moral obligations to humanity.