The Russians are rational. Of course the price of nuclear war was too high to pursue their expansionist doctrine in the Cold War, but their military doctrine is quite different than ours; their strategy is that if they do have to fight a nuclear war they plan on doing their best to win it. We seem to think we don’t have to try to win, but just not let the enemy win. Subtle but significant.
So they take the subject arguably more seriously than we do, which is more defeatist, as is shown by our total abandonment of civil defense in a nuclear war, as well as our dismantlement of a national surface to air missile force in the 1970s when we took down the Nike Hercules system in the US. The Russians continue to modernize theirs.
And the whole concept of nuclear winter is as questionable as the global warming “theory”, having much agenda packed behind it from the anti-nuclear groups in the 1980s who were for unilateral disarmament. The Soviets played along with that free propaganda to their advantage, but they were claimed not to be believers in the end. Some volcanos probably put out more smoke and ash, but the Nuclear Winter idea is nothing that can be proven until tried, not that I want that, but what matters is what our potential adversaries think on the subject.
Considering that much of Russia is already an environmental wreck due to the Soviet era, it wouldn’t take much in the way of nukes to finish them off. You can dig a shelter as deep as you like, but its all for naught if you cant grow anything on the surface. I was going to mention super-volcanoes, the Lake Toba eruption reduced the Human population to less than 50,000. I’m not a scientist, but if it doesn’t take many nukes to produce the same amount of ash, then the planet is screwed. I think that the only people dumb enough to launch salvos of nukes are Islamists, and maybe the North Koreans.