Max Boot fears that it’s forthcoming:
With Ukrainians having overthrown Putin’s ally, Viktor Yanukovych, Putin has ordered a riposte: Russian army units in western Russia and air forces across the country have been scrambled for an unscheduled “exercise.” At the same time, the pro-Russian population of the Crimea, home to an important Russian naval base, has been talking about secession from the rest of Ukraine–no doubt with the Kremlin’s encouragement.
It is by no means inconceivable that the two events could be linked–that Putin could send his troops into part of eastern and southern Ukraine on the pretext of “protecting” the Russian minority, much as Hitler did with Czechoslovakia.
Ukraine expert Alexander Motyl doubts that Russia will be so reckless:
Will Russia lead a charge to reinstall the ancien régime or break off bits of Ukraine? The former scenario is almost impossible, as the regime has melted away and there is no one left to reinstall. The latter is theoretically possible—at least in the Crimea—although it would mean that President Putin has lost all his geopolitical marbles.
If Putin does throw all caution to the wind and acts only on irrational impulse, he will only consolidate democratic rule in Ukraine (nothing rallies people around the flag as much as foreign intervention: even Yanukovych’s financial backer, the multibillionaire Rinat Akhmetov, spoke out against partition on February 24th) and provoke Russian democrats and Crimean Tatars to take to the streets (or, possibly, to arms—in which case, you can kiss the peninsula’s vaunted beaches good-bye). Such action would also be warning Belarus and Kazakhstan that they might be next. When the dust settles, democratic Ukraine will still be standing, Putin’s Russia could be destabilized, and his Customs Union and Eurasian Union would essentially be kaput. An intervention or economic embargo would bring Putin’s Russia nothing at best and enormous risks at worst.