The nuclear launch sites may well be programmed to provide advanced warning when missiles are on their way and automatically trigger a launch. This thought comes from a nuclear layman. What say you nuclear pro’s???
This isn’t about attacking Russian nuclear sites it is a threat from Russia to Ukraine that if Ukraine tries to destroy the attack sites that are launching missiles at Ukraine’s cities then Putin will start WWIII nuclear War.
Launch sites for missiles or aircraft actively being used for attack are fair game.
Likewise would be radar or support elements. If Russia has any of these assets co-located with elements of their nuclear triad, or ABM battle-management systems, it could be dicey. They do have a “Dead Hand,” system which might have some kind of launch-on-warning or launch-on-attack mode.
Not likely