What Putin misunderstands most is that the center of gravity for the former Soviet Union has shifted west. Former Soviet satellites such as Poland and the Czech Republic are prosperous members of the E.U. The nations that made up what was once Yugoslavia have survived their bloody breakup, and most have emerged as strong democracies. Ukraine was set to join this movement toward the European Union last November when Yanukovych suddenly suspended trade and financial talks with the E.U. and accepted what amounted to a $15 billion bribe from Putin to stay in Russia’s camp. To the tens of thousands of courageous Ukrainians who braved the cold and police brutality to protest, Yanukovych’s submission to Moscow looked like an attempt to reverse history.

The opportunity for Putin is almost precisely opposite his atavistic vision of restoration. It is only by moving west, toward Europe, that Russia itself can reverse its demographic and political trap. Year by year, the Russian political system becomes more of a corrupt Oriental despotism — with Moscow closer to Almaty than Berlin. The alternative is for Ukraine to pull Russia with it toward the West…

Putin’s Russia may well make more mistakes: We may see a cascading chain of error that brings Russian troops deeper into Ukraine and sets the stage for civil war. Those are the kind of miscalculations that lead to catastrophic consequences, and Obama would be wise to seek to deter Russian aggression without specifying too clearly what the U.S. ladder of escalation might be.