Nuclear Deterrence

Nuclear deterrence seeks to prevent attack by convincing an adversary that aggression will trigger costs far greater than any expected gain. It works through the threatened use of nuclear weapons rather than their battlefield use. When both sides retain a survivable retaliatory capability, even a conventional war carries the danger of catastrophic nuclear escalation.

How deterrence restrains direct war

Deterrence changes the adversary's calculation by making victory uncertain and the possible cost intolerable.

• A state threatens unacceptable retaliation if the adversary crosses its declared nuclear threshold.
• A survivable second strike capability ensures that an enemy cannot escape retaliation by destroying nuclear forces in a surprise first strike.
• Mutual vulnerability makes leaders cautious because a direct conventional conflict may escalate beyond political control.
• In its extreme form, mutually assured destruction means that both sides can inflict devastating retaliation, leaving neither with a meaningful prospect of victory.

Requirements for effective deterrence

Deterrence depends on capability, credibility and communication. The opponent must believe that retaliation is both possible and politically likely.

• Capability requires survivable weapons, reliable delivery systems, protected command and control, and functioning decision-making arrangements.
• Credibility requires sufficient resolve to retaliate; an implausibly excessive threat may fail to influence the opponent.
• Clear communication of thresholds and consequences reduces miscalculation, although excessive ambiguity or rigidity can itself create danger.
• Deterrence also assumes leaders can interpret signals and make sufficiently rational calculations under severe crisis pressure.

Why deterrence does not guarantee peace

Nuclear weapons may reduce incentives for full-scale direct war, but they do not remove rivalry, violence or escalation risks.

• The stability-instability paradox suggests that confidence against nuclear war may encourage proxy conflicts or limited conventional operations below the nuclear threshold.
• Misperception, false warning, unauthorized use or breakdown of command systems can defeat otherwise rational deterrence.
• During a severe crisis, fear that forces may be destroyed can create crisis instability and pressure leaders to act quickly.
• Arms races and efforts to gain strategic superiority can weaken mutual confidence in restraint.