FRYAZINO, Russia — The elderly former Soviet military officer who answers the door is known in the West as “The man who saved the world.”

A movie with that title, which hits theaters in the United States on Friday, tells the harrowing story of Sept. 26, 1983, when Stanislav Petrov made a decision credited by many with averting a nuclear war.

An alarm had gone off that night, signaling the launch of U.S. intercontinental ballistic missiles, and it was up to the 44-year-old lieutenant colonel to determine, and quickly, whether the attack on the Soviet Union was real.

“I realized that I had to make some kind of decision, and I was only 50/50,” Petrov told The Associated Press.

Despite the data coming in from the Soviet Union’s early-warning satellites over the United States, Petrov decided to consider it a false alarm. Had he done otherwise, the Soviet leadership could have responded by ordering a retaliatory nuclear strike on the United States.