Short answers, pulled from the story.
Stanislav Yevgrafovich Petrov was a Soviet lieutenant colonel in the Soviet Air Defence Forces. On the 26th of September 1983, he was the duty officer at the command center for the Oko nuclear early-warning system when it reported incoming missiles from the United States. He judged the alert to be a false alarm and did not report it up the chain of command, a decision credited with averting a potential retaliatory nuclear strike.
Petrov had several reasons to doubt the alert. A U.S. first strike was supposed to be all-out, making five missiles an illogical opening. The detection system was new and in his view not fully trustworthy. The alert had passed through thirty verification layers unusually fast. Ground radar produced no corroborating evidence even after minutes of delay.
The false alarm was triggered by a rare alignment of sunlight reflecting off high-altitude clouds above North Dakota, which caught the Molniya orbits of Soviet satellites and mimicked a missile launch signature. The error was later corrected by cross-referencing a geostationary satellite.
Petrov was neither officially rewarded nor formally punished for his decision. He was reprimanded for improperly filing paperwork and was reassigned to a less sensitive post. He later took early retirement and suffered a nervous breakdown. He received no commendation because officially honoring him would have required acknowledging flaws in the Oko system, which would have embarrassed his superiors and the scientists who built it.
The incident became publicly known in 1998, when Colonel-general Yuri Votintsev published his memoirs. Petrov had carried the story in effective silence for fifteen years. Widespread media coverage followed the memoirs' publication.
Petrov received the World Citizen Award from the Association of World Citizens in 2004 and again in January 2006 at the United Nations. He received the 2011 German Media Award presented in Baden-Baden and the Dresden Peace Prize on the 17th of February 2013, which included 25,000 euros. On the 26th of September 2018, he was posthumously honored with the $50,000 Future of Life Award at the National Museum of Mathematics in New York.