Did nuclear weapons really keep the Cold War cold?

Perhaps, but the honest answer is that experts disagree. The deterrence argument goes like this: each side's large nuclear arsenal created a state of mutually assured destruction, so neither dared attack the other. John Lewis Gaddis has called the period the Long Peace. The strategist Thomas Schelling brought game theory to the study of deterrence, and Kenneth Waltz listed requirements for successful nuclear deterrence, including that part of a state's arsenal appear able to survive an attack and be used for a second strike, and that the state must not respond to false alarms.

But the peace was odd. The stability–instability paradox says that when two countries have nuclear weapons, direct war between them becomes less likely while minor or indirect conflicts become more likely. During the Cold War the US and USSR never fought each other directly, but they fought proxy wars in Korea, Vietnam, Angola, the Middle East, Nicaragua and Afghanistan.

And some who were closest to the button doubt that skill explains it. Robert McNamara said of the Cuban Missile Crisis that "it was luck that prevented nuclear war," and General George Lee Butler, who commanded US Strategic Air Command in 1991–92, said the Cold War ended without a nuclear holocaust by some combination of skill, luck and divine intervention, mostly the last.