Nuclear Deterrence in 21st Century: Is It Still Relevant After Ukraine War?

Context

• The rift between NATO allies and the U.S especially over Greenland, has shaken European trust in the U.S. as the ultimate security guarantor. At the same time, the expiry of the New START arms control treaty and the ongoing Ukraine war have forced a rethinking of whether nuclear weapons still guarantee security in the 21st century.

Early Nuclear Debate: Certainty vs Uncertainty

At the dawn of the nuclear age, thinkers debated how deterrence works.

• Uncertainty-based deterrence: It states that even ambiguity about nuclear retaliation can deter aggression. An adversary does not need to be sure of a nuclear response; the fear that one might occur can itself prevent risky actions.
  • E.g.: IIsrael follows a policy of nuclear ambiguity—it neither confirms nor denies possessing nuclear weapons. This uncertainty discourages adversaries from escalating conflicts
  • Example: India–Pakistan Before both tested nuclear weapons, neither side had confirmed capabilities. Yet, the possibility that the other might possess nuclear weapons helped restrain full-scale war.
• Certainty-based deterrence: Large stockpiles, tests, and clear doctrines signal assured retaliation
  • Dominated Cold War U.S.–Soviet thinking
  • Over time, certainty prevailed, leading to massive arsenals and arms racing.

Is Nuclear Deterrence Still Effective Today?

The relevance of nuclear deterrence is increasingly questioned because:

• Changing Nature of Global Threats: Earlier, nuclear deterrence focused on preventing state-to-state wars. Today’s major threats include terrorism, cyberattacks, climate change, pandemics, and economic crises, which nuclear weapons cannot deter.
• Limits of Nuclear Weapons in Modern Conflicts: Nuclear weapons are useful only against large-scale military aggression by states. They are ineffective against non-state actors, proxy wars, hybrid warfare, and grey-zone conflicts.
• Risk from Tactical Nuclear Weapons: Newer low-yield or battlefield nuclear weapons blur the line between conventional and nuclear war. This lowers the threshold of nuclear use, increasing chances of escalation by mistake or miscalculation.

Revival of Great Power Nuclear Competition

Despite limitations, great power rivalry has revived nuclear modernisation.

• The U.S., Russia, and China are upgrading delivery systems and warheads
• China is reportedly adding about 100 warheads annually
• The U.K. has reversed earlier plans to reduce its nuclear stockpile.

This renewed focus shows a return to Cold War logic, where security is linked to nuclear strength. However, this thinking ignores today’s complex, interconnected security challenges

Lessons from the Ukraine War on Nuclear Deterrence

• Nuclear Threats Did Not Ensure Military Victory: Russia repeatedly issued nuclear warnings during the war, but nuclear weapons were never used. This shows that possessing nuclear weapons does not automatically guarantee success in a conventional conflict.
• Deterrence Worked Without Nuclear Certainty: Western countries responded through conventional military support, sanctions, and diplomacy, not nuclear threats. Deterrence worked through the certainty of strong retaliation, while keeping nuclear response deliberately unclear.
• Non-Nuclear State Resisting a Nuclear Power: Ukraine, which gave up its nuclear weapons in 1994, has successfully resisted a nuclear-armed Russia. This challenges the belief that only nuclear weapons can ensure national survival.
• Role of Credible Conventional Deterrence: Advanced conventional weapons, intelligence sharing, and alliances raised the cost of aggression for Russia. This proves that strong conventional forces can deter even nuclear-armed states.
• Nuclear Weapons as Political Tools: Nuclear threats by Vladimir Putin were mainly used for coercion and intimidation, not actual use. This highlights the political signalling role of nuclear weapons, rather than their battlefield utility.

Way Forward on Nuclear Deterrence

• Shift from Nuclear-Centric to Integrated Deterrence: Countries should rely more on conventional military strength, cyber capabilities, space assets, and diplomacy, reducing overdependence on nuclear weapons.
• Revive Arms Control and Risk-Reduction Mechanisms: Major powers must restart arms control talks, confidence-building measures, and nuclear risk-reduction hotlines to prevent miscalculation and escalation.
• Strengthen the Norm Against Nuclear Use: The long-standing nuclear taboo should be reinforced through political commitments, restraint doctrines, and international pressure against first use.
• Promote Credible Conventional Deterrence: Investments in precision weapons, air defence, intelligence, and joint military cooperation can deter aggression without crossing the nuclear threshold.
• Adapt Deterrence Thinking to New Threats: Security strategies must address hybrid warfare, cyberattacks, space warfare, terrorism, and climate-driven instability, where nuclear weapons offer limited solutions.
• Encourage Regional Security Frameworks: Regions like Europe should build autonomous but cooperative security architectures, reducing excessive reliance on a single nuclear guarantor.

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