The world came seriously close to a nuclear war during the 1962 Cuban Missile Crisis, when the Soviet Union infamously shipped its intercontinental ballistic missiles to the vicinity of the southern border of the United States. Thankfully, the cold war soon eased and the possibility of a nuclear conflict became considerably remote.
Related conversations were conveniently swept beneath the carpet of the world’s collective thinking. Nuclear-armed nations were expected to become rational actors, exercising self-control in appreciation of the principle of mutually assured destruction (MAD). The fear of a repeat of Hiroshima’s unthinkable horrors was also enough deterrence for anyone.