Mutual Assured Destruction, or mutually assured destruction (MAD), is a doctrine of military strategy and national security policy in which a full-scale use of high-yield weapons of mass destruction by two opposing sides would effectively result in the complete, utter and irrevocable annihilation of both the attacker and the defender, becoming thus a war that has no victory nor any armistice but only effective reciprocal destruction. It is based on the theory of deterrence according to which the deployment, and implicit menace of use, of strong weapons is essential to threaten the enemy in order to prevent the use by said-enemy of the same weapons against oneself. The strategy is effectively a form of Nash equilibrium in which neither side, once armed, has any incentive to disarm thereafter.