my understanding is that 'conventional wisdom' was that country A would not launch a nuclear strike against country B (if country B also had nukes) because if they did, country B would have time and capability to launch a nuclear strike on them before it got wiped out. i think 'mutually assured destruction' was the phrase.
but if country B didn't have nukes, conventional wisdom was that country A could get an invasion force ready, and country B would not want to fight back because country A might press the button.
we didn't have a nuclear war in the 80s - whether that was because of this, i'm not qualified to say.