IIRC the USSR's Seven Days to the Rhine plan hinged on hitting NATO rear areas with nukes ahead of the ground advance. Are we counting that as conventional?
If not: How prepared were Warsaw Pact forces to face NATO with intact rear areas?
opinions over soviet first use of nukes range from "of course" over "they had plans,because you plan everything" to "they didn't want to,and it was used for internal politicking".
they were plenty prepared. They didn't make sure to maintain overhelming conventional superiority just to render it meaningless within minutes.