And yes, nuclear weapons were and are capable of destroying humanity many times over. Not only once or twice did we get close to nuclear war, during the 1962 Cuban Missile Crisis, and then again in 1983 when we forgot to give the Russians the heads up that we were doing some war games which made it look like we had launched a first strike. Our bad! But even though Mutually Assured Destruction prevented direct conflict, there was plenty of hot war in the Cold War. The Korean War saw lots of fighting between communists and capitalists, as did the Vietnam War. I mean, these days we remember the domino effect as silly paranoia, but after Korea and especially China became communist, Vietnam's movement toward communism seemed very much a threat to Japan, which the US had helped remake into a vibrant capitalist ally. So the US got bogged down in one of its longest wars while the Soviets assisted the North Vietnamese Army in the Viet Cong.