The Olympics and recent events in Kiev have placed Russia in the spotlight, and Russian Premier Putin has some choices to make. How big a bite of the apple will he take? The smallest would be to protect the naval base at Sevastopol. This is a given. Any Russian leader would go to war to assure Russia could keep its one warm water seaport. The Black Sea exits into the Mediterranean and that give Russian ships year-round access to the waters of the globe.
The mid-bite would be to safeguard the Russian population of the Crimea. Most of that area identifies with Russia and speaks the Russian language. One resolution would be to partition Ukraine; one part Russian, looking east, and one part more Europeanized, looking west.
The largest bite Putin could take would be to use military force to seize control of Kiev and the national parliament and re-install the ousted president.
Unfortunately, my educated guess is that he will chose to take the largest bite. Five reasons: One, he's Putin. Two, he can get away with it; NATO is not going to invade Ukraine. Third, he can hold off Western aggression by cutting off oil and gas supplies to Ukraine and Europe. Fourth, Russia has used its army to assert its self-interest before, despite huge costs; obtaining a warm water port was the reason Russia invaded Afghanistan. Fifth and most important, Putin is opposed to popular uprisings forcing a change in government; his ongoing support for Assad in Syria is a prime example.
Sadly, Putin is probably going to accomplish a fait accompli, sit back and watch Europe and the United States squirm. There will be no military war, but in Ukraine the war for democracy and government of the people, by the people and for the people, will intensify. It is not a happy scenario.