September 26, 1983

Officer Stanislav Petrov prevented a possible nuclear war.

He was the duty officer at the Serpukhov-15 command post when the missile attack warning system issued a signal about the launch of intercontinental ballistic missiles (ICBMs) from the United States towards the USSR.

The system roared loudly. I was sitting at the control panel, all I could see was the vertical display panel. I saw the banner at the top light up, reading "Start" in red letters. There was no document specifying how long I had to think. (Stanislav Petrov, from a BBC interview)

The Oko system monitored space; it was put on combat alert in 1982. The satellites observed at an angle such that American missile bases were always at the edge of the Earth's visible disk. Launches were detected by infrared radiation from a functioning rocket engine. The system classified single or multiple missile launches as "Start."

At 00:15 AM, the command post's warning system announced that several ICBMs had been launched into Soviet territory. The Cold War was in its escalating phase—three weeks earlier, the Soviet Air Force had shot down a Korean passenger Boeing that had entered Soviet airspace. 269 people were killed.

A minute later, a third missile launched. A fourth missile followed. And a fifth missile. According to the algorithm programmed into the computer, it had already changed the alert from "Launch" to "Missile Attack."

Petrov didn't immediately report the threat to his superiors, but paused briefly to think. He didn't see the flashes and trails of fire from the missiles that signaled a launch. There was no radar confirmation either. Furthermore, he had been instructed that in a real attack, missiles should be launched from several bases simultaneously—"you don't start a war with five missiles."

Petrov reported a false alarm over government communications. It was later discovered that the Soviet satellite had mistaken light beams reflecting off clouds for a missile launch. The world was lucky that the man on duty wasn't just someone skilled in giving and carrying out orders, but an engineer and analyst.