The Man Who Saved the World by Doing Absolutely Nothing
That the U.S. would be lobbing missiles toward its Soviet counterpart would not, of course, have been out of the question at that particular point in human history. Three weeks earlier, Russians had shot down a South Korean airliner that had wandered into Soviet air space. NATO had responded with a show of military exercises. The Cold War, even in the early '80s, continued apace; the threat of nuclear engagement still hovered over the stretch of land and sea that fell between Washington and Moscow.
Petrov, however, had a hunch -- "a funny feeling in my gut," he would later recall -- that the alarm ringing through the bunker was a false one. It was an intuition that was based on common sense: The alarm indicated that only five missiles were headed toward the USSR. Had the U.S. actually been launching a nuclear attack, however, Petrov figured, it would be extensive -- much more, certainly, than five. Soviet ground radar, meanwhile, had failed to pick up corroborative evidence of incoming missiles -- even after several minutes had elapsed. The larger matter, however, was that Petrov didn't fully trust the accuracy of the Soviet technology when it came to bomb-detection. He would later describe the alert system as "raw.
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On September 26, 1983, the world came very close to nuclear war. Shortly after midnight, alarms inside Serpukhov-15 - a bunker in Moscow where the Soviet Union monitored its satellites over the United States - began to go off. The satellites had detected the launch of an intercontinental ballistic missile from a base in the United States.
( via theatlantic.com )