Introduction

The global debate on nuclear deterrence is entering a decisive phase. A visible rupture in transatlantic trust—particularly between Europe and the United States—has coincided with the steady erosion of arms control regimes and the return of great-power rivalry. With landmark agreements such as New START nearing their end and nuclear modernisation accelerating across major powers, long-settled assumptions about deterrence are being re-examined. The question confronting policymakers today is not merely how to deter adversaries, but whether nuclear weapons still deliver the security they promise.

From Cold War Certainties to Strategic Ambiguity

During the Cold War, nuclear deterrence rested on a stark logic: nuclear weapons were the ultimate guarantor of national survival.

• Security depended on the certainty—or deliberate uncertainty—of devastating retaliation.

• The fear of mutual destruction was expected to prevent rational actors from initiating nuclear war.

• In some regions, deterrence relied on ambiguity rather than declared doctrine, as seen in cases such as Israel.

• Despite massive stockpiling, a powerful taboo on nuclear use emerged, reinforced by moral revulsion and global norms.

• This taboo has held since 1945, even at moments of extreme geopolitical tension.

Deterrence thus worked as much through psychology and restraint as through weapons themselves.

A Changing Global Security Landscape

That Cold War equilibrium is now under strain.

• The resurgence of rivalry among the United States, Russia, and China has re-centred nuclear weapons in strategic thinking.

• Major powers are modernising delivery systems, expanding or diversifying warhead capabilities, integrating nuclear options more explicitly into military doctrines

• At the same time, arms control frameworks that once constrained escalation are weakening:

  • Verification regimes are fraying

  • Trust between rivals has diminished

  • Diplomatic channels for risk reduction are narrowing

The result is a world where nuclear weapons are again being treated as active instruments of power, not merely last-resort deterrents.

What the Ukraine War Reveals About Deterrence

The war in Ukraine has provided an unexpected real-world test of nuclear deterrence theory.

• Russia repeatedly issued nuclear threats, yet:

  • Nuclear weapons were not used

  • Escalation remained below the nuclear threshold

• Ukraine, despite being a non-nuclear state, mounted sustained resistance through:

  • Conventional military capability

  • Strong international political and military support

• This experience suggests an important insight:

  • Nuclear weapons alone do not guarantee victory or security

  • Credible conventional deterrence and alliance support can constrain nuclear-armed adversaries

Rather than reinforcing nuclear centrality, the conflict has exposed the limits of nuclear coercion.

Europe’s Strategic Dilemma

For Europe, these developments raise uncomfortable questions.

• For decades, European security has rested on the U.S.-led nuclear umbrella under NATO.

• Growing uncertainty about U.S. political reliability has prompted debate over:

  • Continued dependence on American extended deterrence

  • Greater reliance on French and British nuclear capabilities

  • Alternative, non-nuclear security arrangements anchored in conventional strength and diplomacy

• Europe’s choices will influence on the following front:

  • The future of alliance structures

  • Concepts of strategic autonomy

  • The balance between nuclear and non-nuclear deterrence

How Europe responds may shape global deterrence thinking for decades.

Nuclear Weapons: Privileged but Questioned

What emerges from current trends is a paradox.

• Nuclear weapons are once again being privileged as guarantors of security.

• Yet empirical evidence—from Ukraine and elsewhere—shows that:

  • They do not automatically deliver strategic success

  • They cannot substitute for political legitimacy, economic resilience, or conventional military strength

• The risk is a return to Cold War-style nuclear centrality without the stabilising arms control architecture that once accompanied it.

This raises the possibility that the world is standing at a crossroads.

The Broader Significance

The present moment could mark one of two paths:

• A regression to heightened nuclear dependence, with larger arsenals, weaker norms, and greater risks of miscalculation.

• Or an evolution towards deterrence models that:

  • Reduce reliance on nuclear weapons

  • Emphasise conventional capabilities, alliances, diplomacy, and economic statecraft

  • Treat nuclear arms as residual, not central, security tools

Which path prevails will depend heavily on how major powers—and especially Europe—respond to current crises.

Conclusion

As arms control erodes and nuclear arsenals expand, debates over deterrence are intensifying rather than settling. The Ukraine conflict has demonstrated that nuclear weapons neither ensure victory nor guarantee security, even against non-nuclear adversaries. Europe’s strategic response to this moment—whether it doubles down on nuclear dependence or invests in alternative deterrence frameworks—will play a pivotal role in shaping the future global order. The world may be approaching a turning point where deterrence either returns to its most dangerous Cold War assumptions or evolves beyond them toward a more stable and less nuclear-dependent security architecture.