Why would a country that has so many nukes be afraid of invasion? Genuine question, maybe I am missing something but I see this kind of explanation (Russia afraid of massive land invasion) often and it does not make any sense to me. It feels like applying pre-WW2 logic to world that has fundamentally changed after WW2. Also, if I am mistaken, before Russia attacked Georgia, NATO had like 4 battalions close to Russia and military spending in Europe was going down to ridiculous levels.
Nuclear powers are afraid of invasion because there is a lot of territory between conventional war and the use of nuclear weapons. And because they know that the only real threat of invasion comes from other nuclear powers, meaning once the nukes are fired, the other side fires back and all of a sudden there isn't anything left to defend anymore.
NATO had the local armies of the Baltics, Poland, Slovakia and so on the Russian border (by definition). NATO had the US forces in Germany reasonably close to the Russian border. NATO had the forces supporting the war in Afghanistan on Russians southern border None of that was, as far as anyone not informed about secret NATO planning, can tell geared against Russia. If your neighbor patrols his fence with a huge axe while your children are playing in the backyard, so, you would be worried I assume. Even if it was just to cut wood. Especially if you have bad history with that neighbor.
During the cold war, both NATO and the Warsaw pact conducted war games about invasions of the other side. War Games, because they needed something build their defensive strategies on. As it turned out, both sides, NATO and the Warsaw Pact, never had any real invasions plans for Europe, instead both side focused purely on defense against such an invasion. Turns out that this fear of the other side never died.
Since all that lies in the past, the question where we (as in the West) draws the line. NATO, and the US, kept a ton of unresolved territorial disputes in check since the end of the cold war. Most of those conflicts have the potential to turn really, really bad. If Russia gets away with their attack on Ukraine, others will, potentially rightly so, think they can do the same. And then the World-as-we-know-it might pretty much just end. Well, it might as well if NATO goes to war with Russia over Ukraine as well. Only bad choices it seems.
This is the difference between strategy and grand strategy. Russia is planning not only for 2025 or 2030 but also for 2050 and beyond. Who knows what the world will be then and whether nuclear weapons continue being an effective deterrent. They are falling back to the rules of thumb empires have used for ages. Having a potential enemy at your doorstep can be a bad thing, while having some space between you and potential enemies is probably a good thing.
I am no strategist but I would estimate that right now Russia is generating incredible amounts of hate and fear and turning even those who were kind of indifferent into future enemies. If I naively estimate the probability of this being some rational grand strategy vs probability of this being a move of an old dictator possessed by his ego and some imagined grievances behaving in an irrational way that will damage Russia... I am leaning towards the later one. Of course this is just one example and there are certainly other scenarios/explanations.
I wouldn't make this too much about Putin as a person. Russia has had plenty of leaders with similar ambitions, both in Soviet times and in the empire before it. If leaders like Putin persistently arise in Russia, there must be deeper institutional issues behind them.
