A nuclear war between great powers would mean the collapse of human civilisation – and could lead to the irreversible breakdown of global society. Rhys Lewis-Jones argues that humanity faces an existential nuclear threat that demands deliberate and urgent action
The advent of the Russo-Ukrainian war marked a resurgence of great-power competition and with it heightened nuclear risk. It is the largest-scale conflict in Europe since the Second World War. Over its course, Russia has engaged in aggressive nuclear coercion to limit NATO’s involvement.
For some, this is mere sabre-rattling, but Russia is certainly capable and may be willing to follow through on these threats should it face defeat in Ukraine or get involved a hot war with NATO. One particularly concerning scenario is Russian use of nonstrategic nuclear weapons in a Baltic land grab – a scenario NATO cannot ignore.
If Russia used nuclear weapons in a hot war with NATO, NATO would either have to retaliate and initiate a 'limited nuclear war' or de-escalate and face strategic and political defeat
Deterrence is famously predicated on ‘mutually assured destruction’: an all-out nuclear war. A more plausible scenario is that Russia uses a single or limited number of lower-yield nuclear weapons in a hot war with NATO. This would initiate a game of thermonuclear chicken: NATO can either retaliate or de-escalate. In the case of de-escalation, the Alliance would face strategic and political defeat because Russia could make further demonstration attacks; against NATO airbases, for instance.
If, instead, NATO took the decision to retaliate, it would initiate a ‘limited nuclear war'. It is uncertain whether such an exchange could be halted. Uncontrolled escalation would likely follow.
The discourse in nuclear politics shifted post-Cold War, from NATO-Soviet tensions to nuclear proliferation, arms control and the threat of nuclear terrorism. With the return of great-power competition, however, nuclear risk is heightened and the possibility of systemic war re-emerges: full-scale, multi-theatre conflict between nuclear-armed great powers that mobilises societies, strains command-and-control systems, and threatens to destabilise the international order itself.
Historically, such ‘total wars’ are highly escalatory. They exploit new weapons technology, revitalise the armament industry and trigger full deployment of a nation’s manpower through mass conscription. It is difficult to envisage how a NATO-Russia hot war, or indeed a Sino-American conflict, would manage nuclear risk when the political stakes are so high. Wargames of such scenarios frequently deteriorate into nuclear war, as pressures for victory overwhelm the so-called ‘nuclear taboo’. After all, during WWII, the Manhattan Project developed the atomic bomb, which the US immediately used to catastrophic effect.
While the core precept of national and collective defence is ostensibly survival, what this really means is regime survival. NATO’s member states are willing to accept the risk of nuclear use, reassured by the fact that strategic deterrence held during the Cold War and its crises. NATO may therefore assume that it would also hold in future conflicts. But if, in a Russian demonstration attack, Russia used a nuclear weapon against a NATO military formation or against a major NATO airbase, this would force NATO to choose between conceding defeat or escalating further.
Should such a limited nuclear war escalate to all-out city-targeting, it would likely inflict severe climate damage, as attested by numerous scientific studies on climatic modelling of nuclear winter. Further studies suggest a major nuclear winter would bring about a global famine resulting, according to several models, in billions of deaths.
Studies suggest a major nuclear winter would inflict a global famine, inflicting billions of deaths. It is vital that contemporary policymaking responds to such a threat
Of course, we cannot know; a nuclear war has never been fought. However, it is vital that contemporary policymaking responds to this dire scenario. Low-probability scenarios can be highly consequential. Work on existential risk suggests such catastrophes could end human civilisation and prevent its recovery. So, while the political stakes are high for NATO and Russia, we cannot possibly equate this to species annihilation in a normative sense. What degree of uncertainty over humanity’s survival are we willing to accept in the twenty-first century and beyond?
Nuclear winter represents an objective threat to our species and countless others. Such a threat should motivate a radical transformation of the status quo, yet deterrence practice is increasingly entrenched. A resurgence of great-power competition diminishes the prospects of arms control, let alone nuclear disarmament.
One positive step would be an enduring peace deal over Ukraine. This would at least stabilise relations with Russia. Equally, American political actors with hawkish attitudes to China create a dangerous rhetoric that war is inevitable. For them, the only acceptable course of action is to win a new arms race over conventional and nuclear weaponry. This is misguided.
Any systemic war threatens species annihilation through the immense destructive force of thermonuclear weapons and their climatic effects. Great powers must therefore work towards compromise and de-escalation. Otherwise, Einstein’s warning remains apt: 'I know not with what weapons World War III will be fought, but World War IV will be fought with sticks and stones'.
We cannot sustain real compromise without addressing the underlying dynamics of mistrust. The security dilemma – in which fear of an adversary’s intentions drives spirals of tension – remains the central obstacle. Defensive realists argue it is dangerous but manageable; offensive realists deem it inescapable.
Yet if escalation risks the collapse of civilisation, cultivating a sensibility toward the security dilemma becomes a practical necessity. NATO and other great powers must signal defensive rather than offensive intent, pursuing arms control, and opening channels for dialogue. This is not, however, an excuse for managing nuclear risk over a commitment to global disarmament. This should instead form the basis of future efforts and a restoration of relations.
NATO and other great powers must signal defensive rather than offensive intent, pursuing arms control, and opening channels for dialogue
A peace settlement with Russia could reset relations without excusing aggression. Renewed arms-control talks with Russia and China would affirm that security need not be zero-sum. The long-term goal, however, should be the avoidance of systemic war and general nuclear disarmament. The elimination of nonstrategic nuclear weapons would be a positive step – but in practice, Russia might expect a political trade-off for losing this powerful arsenal.
Without such efforts, the path leads only to deepening mistrust, spiralling arms races, and the possibility of a catastrophic systemic war this century.
