Can you be a hero by choosing to do nothing? Ask Stanislav Petrov, the man who saved the world from nuclear war.

Petrov was an officer in the Soviet Air Defense Forces, monitoring satellites over the U.S. In September 1983, an alarm alerted him that five nuclear missiles were headed toward Moscow. Petrov’s job was to report enemy launches to his superiors, but he believed the warning to be a false alarm. After five tense minutes, he told his superiors that a retaliatory strike was not needed.

Petrov turned out to be correct. A satellite reportedly mistook the sun’s reflection for a missile launch, causing the false alarm.

Although Petrov died in Moscow in May, his death was not widely reported at the time. He was 77 years old.