Yesterday on Fox, George Will said that Russia had to learn to accept its loss of empire -- Ukraine -- as the British did. But I think it he looking at the wrong countries that left the empire. Ukraine is not like India or the Burma, but to Russia it is more like Scotland or Ireland. Scotland is still part of the UK despite a long-running effort to separate, and there was a bitter terrorist war in Northern Ireland over the empire's control which might not be entirely extinguished today.
Not only is Kiev in many ways the first capital and heart of Russia, but the Crimea on the Black Sea is one of Russia's most important naval bases. It is unlikely that Russia and Putin will quietly walk away from these ties, although they may eventually have to give them up. I doubt they will go quietly, whether it means actual fighting or not.
However, I thought during the breakup of the old Soviet Union that the independence of the Baltic countries -- Lithuania, Latvia and Estonia -- was a step too far that would be resisted by Russia. I was wrong; they have been some of the most successful of the old Soviet satellites. But I am guessing that Putin regrets what happened with the Soviet Union disintegrated, and will not let Ukraine go quietly into the night.
One issue that seems to cut both ways for me is the Russian economy. It's not in good shape, and is unlikely to get better as fracking reduces natural gas prices and oil prices along with them. Oil is Russia's main source of foreign exchange. This Russia will be weakened in whatever it does to retain Ukraine, but on the other hand, because of economic pressures, it will be loath to lose an important partner and ally.