Being right

There are few moments in history when the right person is at the right location at the right time and does the right thing and that thing saves the lives of millions or even billions. At a little past midnight on September 26th, 1983 Lieutenant Colonel Stansilav Petrov of the Russian army was that person.

From his wikipedia entry:

Lieutenant Colonel Stanislav Petrov was the officer on duty at the Serpukhov-15 bunker near Moscow. It was his responsibility to use computers and satellites to warn his superiors if there were ever a nuclear missile attack against the USSR. In the event of such an attack, the Soviet Union's strategy was to launch an immediate all-out nuclear counter-attack against the United States.

Just past midnight, on September 26, 1983, the computers indicated that an American missile was heading toward the Soviet Union. Lt. Col. Petrov reasoned that a computer error had occurred, since the United States was not likely to launch just one missile if it were attacking the Soviet Union - it would launch many simultaneously. Also, the satellite system's reliability had in the past been questioned, so he dismissed the warning as a false alarm, concluding that no missile had actually been launched by the United States.

A short time later the computers indicated that a second missile had been launched, followed by a third, a fourth and a fifth. Petrov still felt that the computer system was wrong, but there was no other source of information with which to confirm his suspicions. The Soviet Union's land radar was not capable of detecting any missiles beyond the horizon, so by the time they could make a positive identification it would be too late.

Understanding that if he were wrong, nuclear missiles would soon be raining down on the Soviet Union, Petrov decided to trust his intuition and declare the system's indications a false alarm. After a short while it was apparent that his instincts were right. The crisis put him under immense nervous pressure, yet Petrov's judgement had been sound. A full-scale nuclear war had been averted.

Stanislav Petrov was not originally scheduled to be on duty that night. Had he not been there, it is possible a different commanding officer would have made the opposite decision.