Deterrence Theory

Military deterrence seeks to prevent an adversary's action by convincing it that the expected costs or risk of failure will outweigh any gain. It is relational and psychological: possessing force is insufficient unless the opponent believes both the capability and willingness to use it under stated conditions.

Core conditions of credibility

A credible deterrent rests on the interaction of capability, resolve and communication. Weakness in any one can cause the rival to discount the threat.

• The state must possess military capabilities that can deny the objective or impose costs the adversary considers unacceptable.
• The adversary must believe that the state has the political resolve to act when its protected interests or red lines are crossed.
• Red lines and likely consequences must be communicated sufficiently clearly; excessive ambiguity can encourage probing or miscalculation.
• Capability and resolve must be demonstrated through consistent policy, preparedness and, where relevant, dependable alliance commitments.

Operational foundations

• Deterrence by denial requires defences, resilience and forces capable of making aggression unlikely to succeed.
• Deterrence by punishment requires an ability to retaliate effectively after aggression; nuclear deterrence particularly depends on survivable forces and reliable command and control.
• Threatened responses should be militarily feasible and politically proportionate enough to be believable; an all-or-nothing threat may lack credibility.
• Timely warning, reliable attribution and secure decision-making systems are needed to identify a violation and execute the promised response.

Strategic stability and limits

Deterrence is more stable when both sides understand the consequences of escalation and know that restraint will avert punishment.

• The adversary must be able to connect its contemplated action with the threatened consequence and must value something that can be denied or placed at risk.
• Reassurance, crisis communication and opportunities for de-escalation reduce the fear that compliance will still invite attack.
• Misperception, unequal stakes, accidental escalation and disbelief about resolve can produce deterrence failure even when substantial military power exists.
• Deterrence is harder against actors whose responsibility is difficult to establish or whose objectives and risk calculations are poorly understood.

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