The majority of people in the United States have never heard of Stanislav Petrov, who died earlier this year in the Moscow suburb of Fryazino. News of his death on May 19 is only now being widely reported.​ But Americans—and, indeed, much of the world— owe their lives to the 77-year-old former lieutenant colonel of the Soviet Air Defence Forces. For 25 minutes in 1983, as sensors indicated a U.S. nuclear strike was headed toward Moscow, Petrov kept his cool and decided to report it as a false alarm, reports Sewell Chan at The New York Times. By preventing a retaliatory counterstrike, Petrov likely saved the U.S. and U.S.S.R. from annihilation and the rest of the world from decades of radioactive fallout.

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On that fateful day in September 1983, Petrov was serving as the duty officer at Serpukhov-15, a secret bunker outside Moscow where Soviet forces monitored an early-warning system for nuclear strikes​, Megan Garner at The Atlantic reports.

Petrov's job was to monitor the situation and pass along any signs of a strike detected by the nation's Oko satellites to his superiors, and just after midnight, the alarms began to sound—satellites had picked up five ballistic missiles heading from the U.S. west coast toward Russia.

Colonel Petrov had two choices. He could simply relay the information to his superiors, who would decide whether to launch a counterstrike, or he could declare the incoming missiles a false alarm. If the missiles were a false alarm, he could prevent the advent of World War III. On the other hand, if the missiles were real and he reported them as a false, the Soviet Union would be hit, perhaps critically, without striking back. “All my subordinates were confused, so I started shouting orders at them to avoid panic. I knew my decision would have a lot of consequences,” Petrov told RT in 2010.

He had roughly 15 minutes to make his decision. “My cozy armchair felt like a red-hot frying pan and my legs went limp. I felt like I couldn't even stand up. That’s how nervous I was,” he said.

At the time, a U.S. strike was not out of the question, Chan reports. Less than a month earlier, the Soviets had shot down Korean Airlines Flight 007, which had strayed into their airspace on a flight from New York to Seoul. The crash killed 269 people, including a U.S. congressman. Earlier that year, President Ronald Reagan had publicly referred to the Soviet Union an Evil Empire, and his administration was committed to taking an aggressive stance against the U.S.S.R., backing anti-Communist groups in Central America and undertaking years of military buildup to force the U.S.S.R. into an arms race it couldn't afford.

Despite the high tensions, John Bacon at USA Today reports that several things caused Petrov to hesitate. First, he knew a first strike by the United States would likely be a huge attack, not five missiles. Second, Petrov was not confidant in the Soviet’s satellite alarm system, which was not completely reliable, and ground based radar did not show any missiles in the air. He decided to go with his gut, and reported the incident as a false alarm to his superiors.

As it turned out, the alleged “missiles” turned out to be sunlight glinting off the tops of clouds. Later, Petrov was actually reprimanded for not recording all of the details in his logbook, but he did not receive any punishment for not directly relaying the signal.

Chen reports that Petrov retired from the air force in 1984, and from there, he fell off the radar. At one point he was so impoverished he had to grow potatoes to survive. It wasn’t until 1998, several years after the fall of the Soviet Union, that his role in saving the world from disaster went public, in the memoir of a former Soviet missile defense commander Yuriy Vsyevolodich Votintsev. After that, he gained some prominence and was awarded the Dresden International Peace Prize in 2013 and was the subject of the 2014 docu-drama “The Man Who Saved the World.”