deterrence

Deterrence is a strategy to prevent an actor from taking an undesirable action by threatening significant costs that would result from such action. It is commonly associated with national security and international relations but is applied in crime prevention, diplomacy, and policy.

In broad terms, deterrence operates through deterrence by punishment and deterrence by denial. Deterrence by punishment relies on credible threats to impose costs on the aggressor, such as military retaliation or economic sanctions. Deterrence by denial seeks to raise the costs or reduce the likelihood of success by making the action ineffective or difficult, such as strong defense or fortified borders. In international relations, deterrence includes general deterrence (discouraging any actor from taking an action) and extended deterrence (a great power pledging to deter aggression against its allies). Nuclear deterrence is a prominent form, where the fear of mutually assured destruction aims to prevent war.

Effective deterrence requires credibility, capability, and clear communication of a proportional response. The threat must be believable, the actor must be unable to discount it reliably, and there must be a demonstrated willingness to carry it out. Deterrence can fail through misperception, escalation, prolonged crisis, irrational actors, or misreads of resolve.

Critics note that deterrence can provoke arms races, heighten security dilemmas, or be less effective against non-state actors and instantaneous threats. It remains a central, debated tool in strategic planning and public policy.