Fifty-five years ago, a Soviet submarine officer’s cool head may have prevented World War III. Now, the late hero—Vasili Alexandrovich Arkhipov, who died in 1998 at the age of 72—will be awarded with a posthumous prize that acknowledges his actions, The Guardian reports.

As National Geographic recounts, Arkhipov was 34 years old in 1962, and on a secret submarine mission in the Caribbean. The Cuban Missile Crisis was in full force, and no sea traffic was allowed through the island’s waters. But the U.S. Navy spotted the sub, and began attacking it with depth charges.

What the U.S. Navy didn’t know was that the Russians had a tactical nuclear torpedo onboard. The Russian officers hadn’t heard from Moscow in days, but they’d already received permission to use their deadly weapon if needed. Believing that war was imminent, the submarine’s commander, Valentin Savitsky, decided to fire at one of 11 nearby Navy ships.

“We’re gonna blast them now!” Savitsky exclaimed, according to a report from the U.S. National Security Archive. “We will die, but we will sink them all—we will not become the shame of the fleet.”

Savitsky ordered the nuclear missile readied, and his second-in-command gave the go-ahead. That’s when Arkhipov—who was Savitsky’s equal in rank—came in and talked him down. The officer explained that the depth charges were off-target, and were actually the U.S. Navy’s way of asking them to surface. He refused to approve the missile’s launch—and without his sign-off, the initiative was a no-go.

To commemorate the fateful events from October 27, 1962, the Future of Life Institute—a U.S.-based organization that supports “research and initiatives for safeguarding life and developing optimistic visions of the future,” according to its website—will present Arkhipov’s family members with its $50,000 “Future of Life” prize.

“The Future of Life award is a prize awarded for a heroic act that has greatly benefited humankind, done despite personal risk and without being rewarded at the time,” Max Tegmark, an MIT physics professor and head of the Future of Life Institute, said in a statement quoted by The Guardian.

However, Arkhipov’s descendants believe that his actions were driven by duty rather than heroism.

“He acted like a man who knew what kind of disasters can come from radiation,” said Elena Andriukova, Arkhipov's granddaughter. “He did his part for the future so that everyone can live on our planet.”

[h/t The Guardian]