The reality is that Mr Putin sees holding Ukraine within Russia’s sphere of influence as a vital national interest that he is willing to run pretty big risks to secure. What is more, it seems highly probable that he does not take threats from Mr Obama particularly seriously. He has seen at close hand the American president’s disastrous vacillation over Syria, culminating in the scuttling away from his own red line declaring punishment for the Assad regime if it used chemical weapons. He no doubt also draws conclusions from big American defence spending cuts in the pipeline and Mr Obama’s extreme sensitivity to the war-weariness of American voters.
If Mr Putin believes (as he almost certainly does) that Mr Obama will do little more than deliver a petulant slap on the wrist, he will have no compunction in putting into operation a familiar playbook. (...) While it is easy to criticise Mr Obama’s infinite capacity for thoughtful inaction, the dilemmas for Western diplomacy are real enough. The problem is that like the fox, the West knows lots of different things but is not sure what it really wants, while Mr Putin is like the hedgehog that knows just one big thing, namely that Ukraine, especially in the south and east, is really part of Russia's world.