Much as people carp about the insufficiency of President Obama's response, the entirety of this crisis is governed by the fact that the US has no viable military options and Russia does. (A good example for the United States of why it is important to cultivate sources of strength other than purely military ones.) We know that; Putin knows that. It is difficult to overstate the ease with which Russia can take possession of the Crimean Peninsula since, in effect, it already has possession. It's the home to Russia's Black Sea Fleet. And the peninsula is riddled with Russian military installations, as part of an uneasy post-Soviet accommodation in which Ukraine leases Soviet-era bases to Russia.
I don't agree with the suggestion of this piece in the Telegraph - that it may better for Ukraine to agree to a partition on diplomatic terms rather than face military occupation. But it's right that the post-Soviet history of Ukraine has been marked by neither the country's east nor west being able to successfully or sustainedly unite the country.
The crux of current crisis, or the central issues at stake, is not which slabs of land, in the abstract, should be part of Ukraine or Russia but that borders shouldn't be changed by force or the threat of force. Crimea's current status is the result of a Russian invasion almost a quarter of a millennium ago and a totally arbitrary reassignment of the region from the Russia SSR to the Ukraine SSR in 1954. If history were our guide, the people with the bigger beef or demand for recompense aren't the people in Kiev but the Tatars, Greeks and other ethnic minorities (what's left of them) who were expelled en masse from Crimea after World War II."