Wounded by a personal political defeat in a battle for influence over Russia's Slavic neighbour, Putin is fighting back, and presenting the crisis as a question of symmetry.
In his view, the West "stood by" and allowed armed men to direct events in the capital Kiev - now he is "standing by" as armed men extended their control over the Crimea region.
The former KGB spy blames the West for stirring passions in Kiev, encouraging an opposition to break agreements to restore peace and allowing what Moscow calls "extremists" and "fascists" to dictate political developments in Ukraine.
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Now authorised by parliament to deploy Russia's military in Ukraine to protect national interests and those of Russian citizens, Putin is taking on a West he feels has cut Moscow out of talks on the future of Russia's Orthodox Christian brothers.
How far he will go is the big question.
While Moscow has put 150,000 troops on high alert near Ukraine's border, it has shown no signs, yet, of sending them and denies Ukrainian allegations it sent the protesters who have hoisted Russian flags in some eastern towns.
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Putin is saying nothing in public on Ukraine - and has not done so since Moscow-backed President Viktor Yanukovich was deposed more than a week ago.
At the centre of attention as one Western leader after another calls to urge him not to use force, he is betting the West's response will be weak.
His calculation is that Obama has few levers at his disposal and no appetite for war over a remote Black Sea peninsula with symbolic and strategic value to Russia as home to a Russian naval base, but little economic significance.
The two presidents spoke by phone for 90 minutes on Saturday. The call appeared to have ended in a stalemate.
Reclaiming "lost" property
Putin is banking on salvaging something out of a battle over Ukraine that he appeared to have won when Yanukovich spurned trade and political deals with the European Union in November, but then seemed to lose when Yanukovich was ousted after three months of protests.
"The West told Putin to get lost over Ukraine," said Sergei Markov, a pro-Putin political analyst and director of the Institute for Political Studies in Moscow, underlining the depth of hurt Putin felt over Ukraine.
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Accusing Western powers and international organisations of trying to ignore Moscow in talks on financial assistance for Kiev, Markov said: "What we are saying is that if there are any UN, IMF, G8 agreements without consultations with us, then we will see them as illegitimate."
Reclaiming Crimea, a former Russian territory handed to Ukraine by Soviet leader Nikita Khrushchev in 1954, would win Putin kudos among core voters and especially nationalists.
If the status quo established in the last few days holds, with Russian forces already in charge in Crimea, he can hope to have won back Crimea without a shot being fired in anger or the necessity of taking on another drain to the state coffers.
Even if a pullback is forced on him, Putin will still portray himself as the defender of national interests and those of Russians abroad. In the eyes of many voters, he hopes, he will not have given up Ukraine without a fight.
While he has been busy defending national interests, his lieutenants have been lambasting the West over Ukraine, accusing it of manipulating events and working with a government chosen by gun-toting "extremists".
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Combined with an orchestrated wave of nationalist indignation over attempts to limit use of the Russian language and persecute Russians in a country many consider an extension of their own, Putin's stance plays well at home.
His insistence that Ukraine's new leaders stick to the terms of a European Union-brokered political agreement last month with Yanukovich goes down well.
This month, his popularity ratings have bounced back to almost 70 percent, according to an opinion poll by independent pollster Levada.
"Putin has not forgiven the fact that the agreement was not fulfilled and that is one of his greatest motivations. He considers he is acting in a symmetrical way," said Gleb Pavlovsky, a former Kremlin spin doctor.
"I think that the authorities think it's very helpful that people are getting themselves worked up about this... And the majority feel in a patriotic mood about Crimea and Ukraine. I think it's positive for the Kremlin. They won't refuse action."
Whether he takes action may still depend on the West.
Military intervention in Ukraine has higher stakes than the war Russia fought with Georgia in 2008 - invading Ukraine's southeast could transform Putin, a man who wanted the Sochi Winter Olympics to show Russia's modern face, into a pariah.
If Western powers decide to try to punish Russia with sanctions, Putin will be likely again to pursue a "symmetrical" policy and hit back with similar moves.
This would go down well with core supporters, but might risk unsettling the wealthy businessmen whose support helps cement Putin's grip on power.
But there is a risk Putin could be forced into action over Crimea by the nationalist thinking that he has let loose - and this would be particularly risky if he were pushed into action to defend Russian speakers in eastern Ukraine.
The decision to seek authorisation to send in troops looked less like a prelude to war and more like a threat aimed at getting Kiev and the West to cut a deal, Professor Mark Galeotti from the Center of Global Affairs at New York University wrote on his blog.
"As the language toughens and the troops roll, though, it's getting harder to believe that common sense is going to prevail in the Kremlin."
In broadcasts with Cold War overtones, state television has many times repeated footage of parliament accusing Washington of crossing a red line by warning that Moscow will face "costs" if it intervenes in Ukraine.
It has run image after image of pro-Russian protesters raising the Russian flag above administrative buildings in several eastern regions, including the industrial centres of Donetsk and Kharkiv.
The patriotic mood has caught on. For every dissenter wondering whether this is the worst thing Russia could do since it crushed opposition in Czechoslovakia in 1968, there are dozens more who say the West is fomenting violence.
Near Red Square and the Defence Ministry in Moscow on Sunday, a few hundred protesters waved banners calling for "No War". Dozens were detained.
But their numbers could not match the thousands who turned out for a demonstration for the "defence of the Ukrainian people" in central Moscow.
"Fascism will not win," the protesters chanted. "Crimea is Russia. We are for Russian unity."
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