September 26, 1983: False alarm in the Oko system

On September 26, 1983, Lieutenant Colonel Stanislav Petrov, an officer of the Soviet air defense forces, was on duty at the Serpukhov-15 command post near Moscow. His missile attack early warning system, Oko, reported the launch of American intercontinental ballistic missiles: first one, and soon four more.

The year had been extremely tense. Three weeks earlier, Soviet fighter jets had shot down a South Korean passenger plane, killing 269 people. The Soviet leadership seriously expected a surprise attack and launched Operation RYAN to make sure it did not miss its preparation.

By the logic of the time, a launch signal meant an immediate retaliatory strike was required. Petrov did not pass it up the chain right away and decided to wait for confirmation. The confirmation never came.

Petrov judged the signal to be an error. A massive first strike by the United States would have looked different: it would have meant hundreds of launches at once, not five missiles. The reliability of the new satellite system had already raised questions, and ground-based radars could not see targets beyond the horizon and confirmed nothing.

Later it was established that the system had mistaken a rare coincidence for a launch: sunlight was reflecting off high-altitude clouds, and the Oko satellites were in elongated orbits. The error was subsequently corrected by cross-checking data against a geostationary satellite.

The incident was only made public in 1998. Petrov was initially praised but received no award, and was later transferred to a less sensitive post; he himself recalled suffering nervous exhaustion. Stanislav Petrov died in 2017.

That day is still called one of the closest approaches to accidental nuclear war. The automation was confidently wrong, but a human decided the outcome.

Image: Queery-54 CC BY-SA 4.0 · License

Translation editors: Соловьев В., Пеков А.