Jesus fucking Christ, I never knew this. Right now I'm holding on to the desk for dear life. Jesus fucking H bastard in a bun on a bike Christ.

From Wikipedia, though originally read about in this excellent Edge article.

Vasili Alexandrovich Arkhipov was a Soviet naval officer. On October 27, 1962, during the Cuban Missile Crisis, a group of 11 United States Navy destroyers headed by the aircraft carrier USS Randolph entrapped a nuclear-armed Soviet Foxtrot class submarine B-59 near Cuba and started dropping depth charges. Allegedly, the captain of the submarine, Valentin Grigorievitch Savitsky, believing that a war might already have started, prepared to launch a retaliatory nuclear-tipped torpedo.

Three officers on board the submarine — Savitsky, Political Officer Ivan Semonovich Maslennikov, and Commander Arkhipov — were entitled to launch the torpedo if they agreed unanimously in favour of doing so. An argument broke out among the three, in which only Arkhipov was against making the attack, eventually persuading Savitsky to surface the submarine and await orders from Moscow. The nuclear war which presumably would have ensued was thus averted.

At the conference commemorating the 40th anniversary of the Cuban Missile Crisis held in Havana on October 13, 2002, Robert McNamara admitted that nuclear war had come much closer than people had thought. Thomas Blanton, director of the National Security Archive, said that "a guy called Vasili Arkhipov saved the world."

And from this 2002 Boston Globe article

Participants emphasized that any new knowledge should be used to help avoid future conflict, in particular a potential US war with Iraq. ''God willing, someone will be sitting down in Baghdad and talking about this moment in 40 years'' if a war is averted, said Christopher Kennedy Lawford, President Kennedy's nephew. Lawford, who played a US pilot in a film about the crisis, ''13 Days,'' was among several members of the film's team attending the conference.