Stanislav Yevgrafovich Petrov (Russian: Станисла́в Евгра́фович Петро́в; born c. 1939) is a retired lieutenant colonel of the Soviet Air Defence Forces. On September 26, 1983, he was the duty officer at the command center for the Oko nuclear early-warning system when the system reported that a missile was being launched from the United States. Petrov judged the report to be a false alarm, and his decision is credited with having prevented an erroneous retaliatory nuclear attack on the United States and its NATO allies that could have resulted in large-scale nuclear war. Investigation later confirmed that the satellite warning system had malfunctioned.