Putin is NOT Hitler, nor is Ukraine the Sudentenland
Let's not lose perspective here. Putin isn't Stalin, and the current commonwealth of Russia isn't the Soviet Union.
Putin is -to his lights- merely setting things right after the chaos of the USSR's fall. He's not bent on world domination, nor is China for that matter.
While WW2 is a useful piece of history, it's only one piece, nor does history repeat itself. We need to stop viewing every event through the lens of 1939-1945. Those who frantically condemn Putin as some sort of Hitler-wannabee monster miss the point; they are thinking like Westerners, while Putin is thinking like a Russian.
Given that the Ukraine has been under the control of either Poland or Russia for the past several centuries, it is less than sensible to cast this as the first step towards world domination. Neither Russia nor China are our enemies. They are, rather, our competitors.
North Korea and the current Iran regime would be more accurately described as enemies.
I expect that Russia will take the Crimea and a slice of (Russian-speaking) eastern Ukraine is the most likely outcome.