Moscow cannot do the job without forcibly suppressing the western half of Ukraine. Such a war would be the most dangerous crisis in Europe since 1945 and one wonders whether the Putin government could survive a catastrophically expensive war and the ensuing isolation. Unless the intervention was lightening fast and the opposition was quickly suppressed, the cost of the war and the cost of pacifying and developing Ukraine in the aftermath would almost certainly wreck the Russian economy.

On the other hand, Putin would have grave difficulties surviving the loss of all Ukraine. The example of a popular revolution against a Moscow-leaning government is horrifying and destabilizing enough. Hatches are being battened down from Kaliningrad to Vladivostok as the FSB (ex-KGB) does its best to prevent any kind of contagion. The consequence of a united Ukraine joining the West would be infinitely worse. Putin’s dream of a Eurasian Union would suffer an irrevocable and decisive defeat. The loss of Crimea would infuriate Russian nationalists beyond endurance, and Putin would look helpless and weak in a political culture that worships only strength and success.

A rationalist would suggest to the Kremlin that partition was its best hope. Solzhenitsyn once gloomily speculated that the Ukrainians on the west bank of the Dnieper were lost to the Russian motherland as a result of Soviet history; the Kremlin might well think about trying to move quickly towards a de facto partition with the dividing line as close to that river as possible in the north, and stretching across it to Moldova in the south. It would be surprising if the Kremlin has not entertained the possibility of partition as a second-best outcome and wouldn’t switch quickly to promoting it if all hope of absorbing the whole country is lost.