Russia isn't going to invade Poland or any Nato country. They know they will be destroyed and humiliated. Its non nato countries who have a good cause for worry.
It sounds crazy to me too, I'll admit, and these plans were made before the Russian armed forced showed themselves to be so wildly incompetent in comparison to NATO. The thinking was that if Russia invaded like they're doing in Ukraine, they'd be pushed back and that would be the end of it.
But now Russia know they would lose a conventional war, and while this is good news in general, Russia are desperate. They see their post-Soviet borders and indefensible, and feel they must hold most of the territory they had as the USSR to narrow the points of entry, so they would actually have enough soldiers to successfully defend itself. They've gone from holding 1 of 9 entry points after the collapse to 5 iirc as of now.
He thinks this is why they're talking about nukes, because they would need to use tactical nukes to have any hope of beating NATO forces, or more likely terrorizing people into submission (which I don't think it's likely either).
From a demographic standpoint, Russia's population is collapsing even faster than Europe, their pool of 18-40 year olds in ideal draft age will be half what it is now in 20 years, leaving them with a force incapable of holding the vast planes of western Russia. And even if they believed no one in Europe would invade them currently, they're worried about what might happen in 100 years.
Nevermind that Europe will have a population collapse as well, and none of their borders are defensible either, of course.
Again, this is all from Zeihan.
