mutual assured destruction

Political and military doctrine that asserts that the relationship between nuclear powers remains stable if they are able to destroy each other. It reflects the theory of deterrence: that a potential aggressor will be discouraged from launching a ‘first strike’ nuclear attack by the knowledge that the enemy is capable of inflicting ‘unacceptable damage’ in a counterstrike.

The doctrine is particularly associated with the nuclear arms race between the USA and the USSR during the Cold War (1945–89). The subject of great moral debate, it espouses the idea that a country's population is best protected by leaving it vulnerable, so long as the adversary is equally vulnerable. The USA and USSR both had ample nuclear might to inflict ‘unacceptable damage’ that would eliminate each other as world powers during the Cold War. ‘Unacceptable damage’ is defined as 25% of the population and 50% of industry.

Towards the end of the Cold War the USA began to look for a more tangible means of defence, and began to develop the concept of a nuclear missile defence system that would destroy incoming missiles before they reached their target. The first programme (1983–93) was the Strategic Defense Initiative (SDI), which was named Star Wars because it was to be based partly outside the Earth's atmosphere. The programme, had it succeeded, would have altered the balance of mutually assured destruction.

SDI was later replaced by the National Missile Defense (NMD) programme, a less ambitious system that aims to protect the USA from a limited nuclear missile attack, the threat being considered to come from ‘rogue’ states such as Iraq or Korea.