





During the Cold War, the United States and the Soviet Union each built a stockpile of nuclear weapons. Soviet policy rested on the conviction that a nuclear war could be fought and won. The United States adopted nuclear deterrence, the credible threat of retaliation to forestall enemy attack.

To make its threat convincing, the United States during the 1950s developed and deployed several types of delivery systems for attacking the Soviet Union with nuclear weapons. By the 1960s, three such systems emerged as the basis of strategic deterrence:

long-range manned aircraft carrying nuclear bombs land-based intercontinental ballistic missiles with nuclear warheads, and nuclear-powered submarines armed with nuclear ballistic missiles.

Each system became one independent leg of what was called the Strategic Triad. Any one of the three alone was powerful enough to deter attack. Because no enemy could realistically hope to destroy all three at the same time, the Triad seemed almost invulnerable.