The “stand-off” in 1983 lasted minutes, not days like the Cuban Missile Crisis some 20 years earlier, but could have likewise led to full-blown nuclear war between the U.S. and USSR: Soviet early-warning systems detected a nuclear attack coming from the United States. The natural response would have been a counter-strike by Moscow. The result, as one Stanford professor wrote later, could have been “roughly a hundred million people blown apart, burned up and poisoned on the first day of the war.” (Within months, he estimated, the death toll could have reached a billion.)
The decision that prevented that from happening was made by a Soviet officer working the night shift at a secret military facility outside Moscow who determined, in the 10 minutes he had to make the call, that the alarm was false. His name was Stanislav Petrov.