Today is the 30th anniversary of Petrov Day. What’s Petrov day, you ask? Well, as described on LessWrong:
The story begins on September 1st, 1983, when Soviet jet interceptors shot down a Korean Air Lines civilian airliner after the aircraft crossed into Soviet airspace and then, for reasons still unknown, failed to respond to radio hails. 269 passengers and crew died, including US Congressman Lawrence McDonald. Ronald Reagan called it “barbarism”, “inhuman brutality”, “a crime against humanity that must never be forgotten”. Note that this was already a very, very poor time for US/USSR relations. Andropov, the ailing Soviet leader, was half-convinced the US was planning a first strike. The KGB sent a flash message to its operatives warning them to prepare for possible nuclear war.
On September 26th, 1983, Lieutenant Colonel Stanislav Yevgrafovich Petrov was the officer on duty when the warning system reported a US missile launch. Petrov kept calm, suspecting a computer error.
Then the system reported another US missile launch.
And another, and another, and another.
What had actually happened, investigators later determined, was sunlight on high-altitude clouds aligning with the satellite view on a US missile base.
In the command post there were beeping signals, flashing lights, and officers screaming at people to remain calm. According to several accounts I’ve read, there was a large flashing screen from the automated computer system saying simply “START” (presumably in Russian). Afterward, when investigators asked Petrov why he hadn’t written everything down in the logbook, Petrov replied,”Because I had a phone in one hand and the intercom in the other, and I don’t have a third hand.”The policy of the Soviet Union called for launch on warning. The Soviet Union’s land radar could not detect missiles over the horizon, and waiting for positive identification would limit the response time to minutes. Petrov’s report would be relayed to his military superiors, who would decide whether to start a nuclear war.
Petrov decided that, all else being equal, he would prefer not to destroy the world. He sent messages declaring the launch detection a false alarm, based solely on his personal belief that the US did not seem likely to start an attack using only five missiles.