@the5thColumnist In 1979 a technician inserted a training tape into a NORAD computer (by mistake) that simulated a Soviet attack on the US. It could be that or the 1980 incident you're thinking of: https://nsarchive.gwu.edu/briefing-book/nuclear-vault/2020-03-16/false-warnings-soviet-missile-attacks-during-1979-80-led-alert-actions-us-strategic-forces