FRYAZINO, Russia (AP) — 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.

What made this even more dangerous was that the Soviet Union appears genuinely to have feared a surprise U.S. nuclear attack during what was an exceptionally tense period of the Cold War. That month, the Soviets had shot down a passenger plane flying to South Korea from the U.S., suspecting it of spying. The United States, after a series of provocative military maneuvers, was preparing for a major NATO exercise, called Able Archer, which simulated preparations for a nuclear attack.

In the movie, “The Man Who Saved the World,” by Danish director Peter Anthony, actors portray the events of that night in 1983. The dramatic scenes are interwoven with footage of the real Petrov as an older man at his home in Russia, and on a 2006 trip to the United States, where he receives an award at the United Nations and meets with movie stars, including Kevin Costner, Matt Damon and Robert De Niro.

In his homeland, Petrov’s role in history has won him little fame. He still lives in Fryazino, a town on the outskirts of Moscow, in a simple, unkempt apartment that looks much as it does in the movie, down to the long strip of yellow fly paper hanging from the ceiling. Unlike in the movie, where Petrov is shown angrily chasing out foreign journalists who have come to hear his story, he proves a gracious host, welcoming guests into his kitchen.

When Petrov, now 76, looks back on that night at the secret Serpukhov-15 control center, he remembers the sound of the alarm that shattered the silence shortly past midnight.

“It was this quiet situation and suddenly the roar of the siren breaks in and the command post lights up with the word ‘LAUNCH,'” he said. “This hit the nerves. I was really taken aback. Holy cow!”

He stood up and saw that the others were all looking at him in confusion. “My team was close to panic and it hit me that if panic sets in then it’s all over.” He needed to make a decision.

In the movie, Petrov speaks of not wanting to be responsible for setting off a nuclear war. But in the AP interview he suggests this was more of the filmmakers’ poetic license.

“Sorry, I didn’t have time to think about whether I would be the one who started World War III,” he said. “I had to decide how reliable the information sent by the computer was.”

Within minutes of the first alarm, the siren sounded again, warning of a second U.S. missile launch. Soon, the system was reporting that five missiles had been launched.

Petrov reported to his commander that the system was giving false information. He was not at all certain, but his decision was informed by the fact that Soviet ground radar could not confirm a launch. The radar system picked up incoming missiles only well after any launch, but he knew it to be more reliable than the satellites.

The false alarm was later found to have been caused by a malfunction of the satellite, which mistook the reflection of the sun off high clouds for a missile launch.

Petrov was not rewarded for his actions, most likely because doing so would have brought to light the failure of the Soviet’s early-warning satellites. Although his commanding officer did not support Petrov at the time, he was the one who revealed the incident after the Soviet Union collapsed in 1991. If Col. Gen. Yury Votintsev had not spoken out, Petrov said he himself “would have forgotten about it like a bad dream.”

Ret. Maj. Gen. Vladimir Dvorkin, an expert on Russia’s strategic nuclear forces, played down the importance of the decision forced on Petrov, saying the Soviet leadership in any case would have waited for confirmation from the radars before launching a retaliatory attack.

What’s more, Dvorkin said, Russia no longer even has full satellite coverage of the United States, and relies fully on its radar network to monitor U.S. nuclear forces.

“The situation in Russia today is such that the satellite system doesn’t work at all, and this doesn’t frighten anyone too much,” he said. “As you can see, everyone is living peacefully, without panic.”