Definition
Nuclear deterrence is a security strategy in which a state prevents an attack by maintaining the credible threat that any aggression will be answered with devastating nuclear retaliation. The goal is not to win a war but to make war too costly to start.
The strategy took shape during the Cold War, as both the United States and the Soviet Union built large nuclear arsenals. Its central logic became known as mutually assured destruction: because neither side could survive a full nuclear exchange, neither side dared begin one.
Why it matters
How it works
Deterrence depends on the attacker believing that retaliation is both certain and unsurvivable. States therefore built second-strike capability — weapons hidden in submarines, hardened silos, and mobile launchers — so that even a surprise attack could not disarm them.
The danger of the strategy lies in its assumptions. It requires leaders to behave rationally, communication channels to remain open, and no accident or miscalculation to trigger an exchange. Crises and false alarms during the Cold War showed how thin that margin could be.