It is a mistake to see Putin as mad, paranoid, or motivated by an inflated ego. His posture is that of an old-school Soviet intelligence officer.
AIUI, Ukraine cannot join NATO at the moment; it doesn't control its own borders (Crimea, Donbas).
If Russia annexes Donbas, then they're back to the previous problem: NATO on the border. Note that Russia has not annexed the part of Georgia they invaded; it is now supposedly an independent republic. My guess is that they would settle for independent republics in Donetsk and Luhansk. They don't want Global Nuclear War any more than we do. It's a shame Ukraine didn't agree to give them autonomy earlier; now it looks like Russia is determined to destroy the Ukrainian military infrastructure, and autonomy isn't any longer up for discussion.
AIUI, Ukraine cannot join NATO at the moment; it doesn't control its own borders (Crimea, Donbas).
If Russia annexes Donbas, then they're back to the previous problem: NATO on the border. Note that Russia has not annexed the part of Georgia they invaded; it is now supposedly an independent republic. My guess is that they would settle for independent republics in Donetsk and Luhansk. They don't want Global Nuclear War any more than we do. It's a shame Ukraine didn't agree to give them autonomy earlier; now it looks like Russia is determined to destroy the Ukrainian military infrastructure, and autonomy isn't any longer up for discussion.