The cold war and Mutually Assured Destruction. I was born in 1958, on a DEW line (Distant Early Warning) station in Churchill, Manitoba. It was one of dozens of such radar stations staffed by American and Canadian military personnel(dad was a cook), in a joint effort to detect the approach of nuclear missiles from the USSR. So we could launch our own missiles before the Russian missiles reached their targets, and their cities would die about 12 minutes after we died. Thus mutually assured destruction, and the detente that was called the cold war. NATO vs. the Communist Bloc. WWIII was commonly touted in the media as non-survivable at a planetary level. Both sides were wary of engaging in a frontal war of the scale of the first two world wars for fear that the conflict would escalate to a nuclear exchange and worldwide devastation. They called it nuclear winter.

http://en.wikipedia.org/wiki/Mutual_assured_destruction

So they had little proxy wars instead, each side feeding rebel groups and dictators with weapons and training cadres of elite troops, seals vs. spetsnaz in Korea, Viet Nam, South America, the Middle East, Africa. Spies stealing technological blueprints with mini cameras, crossing borders in the dark.