Call me silly, but i dont think this is an actual problem for putin. He just wants ukraine territory. All the nato bullshit is just an excuse. There is no way he actually would have messed with an EU country. Ukraine and moldova, and to an extend georgia, are the only invadable countries in europe. And he has his foot already in the door of all three. And with invadable i mean countries he cant comfortably use as a puppet state like most of central asia, belarus, and so on.