Background to the incidentEdit
They knew there early launch radar was unreliable as they found out in The 1983 Soviet nuclear false alarm incident and so was of little if any use to them.
1983 Soviet nuclear false alarm incident occurred on the n the night of September 26, 1983, when the Soviet orbital missile early warning system (SPRN), code-named Oko, mistakenly reported a single intercontinental ballistic missile launch from the territory of the United States.
It's commander, Lieutenant Colonel Stanislav Petrov, who was on duty during the incident had the intelligence to correctly disregard computer error.
This was because ground based early warning radars did not detect any launches, a planned full-scale nuclear attack from the United States would involve hundreds, if not thousands, of simultaneous launches rather than just single missile and he also the spy satellite was known to be faulty.
They knew there early launch radar was not just unreliable, but now a known liar.