Nuclear doctrine, and you can see this very clearly in the latest US Defence Posture, is evolving towards a more selective and escalatory approach to nuclear weapons.
As I've repeatedly said, any invasion of Russia from the west would, by definition, be existential given Russia's geography. Only the US would ever be capable of doing this, and it would need a massive force build up in Europe is preparation. Thus I'm talking about the end of a very long road, not the beginning.
The battlefield use of tactical nuclear weapons is old stuff, and certainly likely in that situation, which I think you agree with.
What I don't agree with is RV's totally inane analysis that nuclear weapons would never be used due to Russia's assured destruction, and that therefore Russia would be forced to surrender in a conflict with the US which he seems to believe could safely be kept conventional. That analysis is just plain stupid, and shows no grasp of escalation dominance under MAD which would actually put far more pressure on the US to desist from its own aggression than it would put on Russia to stop defending itself.