Deterrence theory gained increased prominence as a military strategy during the Cold War with regard to the use of nuclear weapons. It took on a unique connotation during this time as an inferior nuclear force, by virtue of its extreme destructive power, could deter a more powerful adversary, provided that this force could be protected against destruction by a surprise attack. Deterrence is a strategy intended to dissuade an adversary from taking an action not yet started, or to prevent them from doing something that another state desires. A credible nuclear deterrent, Bernard Brodie wrote in 1959, must be always at the ready, yet never used.

Mutual assured destruction, or MAD, is a doctrine of military strategy and national security policy in which a full-scale use of nuclear weapons by two or more opposing sides would cause the complete annihilation of both the attacker and the defender (see pre-emptive nuclear strike and second strike). It is based on the theory of deterrence, which holds that the threat of using strong weapons against the enemy prevents the enemy's use of those same weapons. The strategy is a form of Nash equilibrium in which, once armed, neither side has any incentive to initiate a conflict or to disarm.