I was unclear. Russia's military threat to Nato is simply a soft invasion by supporting paramilitary uprisings such as that in Moldova and Ukraine. It's more about Putin's prestige as the defender of greater Russia than any actual substance in protecting a minority. Russia probably does perceive a real threat of Nato and the US moving to make Russia's nuclear threat less of an actual threat. But, the question is whether Nato can allow Russia to continue its soft invasions.
Russian fears are exaggerated in line with their leaders ambitions. But a Barbarosa against Russia today is not that far from Moscow at start.
Also people who live in the Eastern Ukraine are suffering massively in this continual conflict and the innocent are dying in this fight. Putin keeps the conflict going like an open wound on the Ukrainian state but he has not been clear about what he actually wants. I suspect he wants it all but realistically a the Crimea and perhaps Donetzk is the most he can expect. This callous indifference to the loss of life being incurred has undermined his reputation and the passion of the locals for Russian rule.
He has not done these soft tactics in any NATO state though Russian groups have been on peaceful marches in the Baltics for instance and there was a lot of Facebook activity by pro Russians at the outbreak of the Ukrainian problem.
We would not need a missile shield so much if we could establish clear boundaries.
Putin invaded Georgia on W Bush's watch, so I can't see him as much of a strong leader in Europe. He's not the man his father was, or even Clinton. But, Obama's foreign policy is inconsistent, and was initially naïve.
Bush would probably also have considered the ukraine like Georgia to be Russias back yard. The Cuba or Mexico of Russia. Obamas activity in opposing Russian aggression was magnified by his ambitions to squeeze Russia here. But his policy in the Ukraine increasingly appears to have been a unilateral American one or if the EU was involved a badly thought through one which failed to consider the costs of such ambitions and what they would provoke