This is a good article on why Putin and Russia are reacting as they are to Ukraine potentially joining NATO. The geography of Western Russia is very much in favour of the invader rather than the defender. To compensate, buffer zones have always been the way forward. Arguably, the recent big invasions of Russia (France and Germany) have failed because of stretching the supply chain of the invader. When winter followed by the spring thaw comes, it get very difficult to move supplies long distance.
In that respect, you can partially understand why Putin is getting a bit twitchy about having a potential adversary to the south who also owns one of Russias only warm water ports.
It will be interesting how we get out of this. The Russian psyche likes a strong leader so for Putin to back down now would be career limiting to say the least. He therefore needs to 'win' in some way to not appear weak to both his supporters and rivals in Russia. In the old Soviet days, there could be concessions from the West given without the public in the West knowing. On the face of it, the Soviet Union backed down in the Cuban Missile Crisis but it did lead to the removal of US missiles in Turkey and Italy which directly threatened the Soviet Union. This was Kruschevs 'win' or, at worst 'draw' over the whole affair