Mr Putin simply could not interpret the ousting of Mr Yanukovych, after the Ukrainian leader had refused to sign an association agreement with the European Union (EU) in favour of an agreement with Russia, as anything other than a new attempt by the Western world to continue shrinking Moscow's sphere of influence. The flurry of American and European dignitaries who flew to Kiev in order to encourage pro-EU and anti-Moscow demonstrators - they also assured the protesters of their support - could not but reinforce the Russian president's impression. What pushed Mr Putin to react even more strongly was the fact that Crimea, where the majority of the population is of Russian origin, is the seat of the Russian navy in the Black Sea - a crucial strategic outpost. In addition, Ukraine itself has tremendous strategic and symbolic value for Russia; a significant part of the country outside Crimea - especially in the east - comprises a very important segment of the population of Russian origin, or Russophile.
Therefore, one wonders what EU High Representative for Foreign Affairs Catherine Ashton, US Senator John McCain and US Assistant Secretary of State for European and Eurasian Affairs Victoria Nuland had in mind when they were - de facto - encouraging the protesters at the Maidan square in Kiev to continue with what was increasingly becoming an insurrectional movement involving a mixed bag of various forces.
It had to be envisaged - this is supposedly the role of strategic planning outfits in any foreign affairs or defence ministry - that Mr Putin was not going to sit on his hands. He would be even less inclined to do so since he knew that a show of force and a de facto takeover of Crimea would not be met by a military response from the United States and/or Europe. In that respect, the hype at the end of February in the American and European media about the "danger of war" in Europe was irrelevant talk. It takes two parties to have a war, and the Ukrainians - divided, bankrupt and disorganised - aren't in a position to wage even a rearguard battle.
So, taken flat-footed as they were, the Obama administration and the Europeans have been scrambling for an answer. They are caught in a dilemma: on the one hand, they need to send Mr Putin a message that should be stronger and more convincing than their meek reaction to the de facto annexation of Ossetia in August 2008; on the other, their options are limited.
US President Barack Obama is a pragmatist. He looks at such situations by balancing costs and benefits, and evaluating practical feasibility of any policy or action on the foreign front. He knows that after the loss of credibility generated by his flip-flop on Syria, he needs to show his Russian counterpart that he means business and that the cost of doing nothing - or close to nothing - will be high. At the same time, however, he has limited scope for manoeuvre. He cannot pretend that a possible military action is on the table. And the use of sanctions will be extremely delicate to manage, given the fact that Russia has the power of veto in the United Nations Security Council and that there are quite a number of American and European business and economic interests that will be badly hurt if Moscow engages in a tit-for-tat game.
The situation is made even more complicated for the West by the fact that neither Germany nor the United Kingdom is ready to endorse sanctions that would harm their interests in, and their economic relationship with, Moscow. More than 6,000 German companies operate in Russia, and London benefits a lot by being the platform of choice for the financial dealings of Russian tycoons and companies. Moscow is also a key gas and oil supplier for Europe, especially for Germany. Even though it could be replaced in that role, this would not be without serious disruptions.
Drawing a comparison with Iran - how sanctions brought that country to the negotiating table - and concluding that sanctions would have the same result for Moscow, as is sometimes heard in Washington circles, demonstrate plain ineptitude: Russia is not Iran. Similarly, a choice between Russia remaining a member of the G8 (assuming there would be unanimity to expel it, which is subject to question) and keeping control of at least part of Ukraine - including Crimea - will be a no-brainer for Mr Putin.
Moscow has made its objective plain: it wants to have something similar to the agreement achieved on February 21 between Mr Yanukovych and the Opposition, which was rendered void by Mr Yanukovych's fall. The agreement was meant to give the Russian-speaking regions of Ukraine a greater say in the government and more legal protection, thus ensuring Moscow's influence on the future of Ukraine. Short of a move to engineer a full secession of Crimea by way of a referendum - which remains on the cards - Mr Putin will not be satisfied with anything less. He has also kept his options open on whether he will recognise the results of the presidential election in Ukraine scheduled for next May, and on whether he will step up military pressure if he considers the fact that the "threats" - as he defines it - against the security and lives of Ukrainians of Russian origin are increasing.
It is not clear whether actual sanctions - and which ones - would be decided on by the US and Europe against Russia. But even if there will be sanctions, a reasonable bet is that they will not deter Mr Putin from his objectives. It is most likely that the new government in Kiev will have to accommodate Moscow's priorities and concerns. This is shaping as the endgame - for the moment at least. The rest will be diplomatic ballet and fine-tuning.