Consider

Consider the possibility President Putin isn't as much interested in Ukraine as many experts seem to portray his interests there but to test the willingness and resolve of the European Union against their own economic interests and dependency on Russian natural gas and oil.

His interest in Ukraine is political as he had a crony there as the puppet president who was ousted after public protests after which the people discovered he and his friends had used the government and Russian aid to bolster their own financial interests and wealth.

His interest in Ukraine was to unsettle the government where the people would oust the government and he can establish a new puppet president, except he now knows the majority of the people are for their government and want their soverignty and independence for themselves and from Russia.

So he settled for the Crimean peninsula, which was an invastion and occupation for the offshore oil rights than the land, government or people, and for the eastern border area with the majority of Russian heritage, except the local militias weren't armed or experienced for a civil war.

And that's why he sent experienced troops and leaders along with heavy weapons, including artillery, tanks, and personnel carriers, and now we know included surface-to-air missiles which shot down the commerical aircraft with 298 people on board. 

Depsite all that, his goal may be simply a political test of the resolve and willingness of the EU to support Ukraine through the fighting in their country with the Russian backed and supported pro-separatists. 

He knows the US can and will add sanctions against selected Russian people and companies, but he's testing if President Obama will include sanctions against US companies working in Russia or with the Russian government, especially energy and airplane production companies.

But his real goal may just be to push the EU using their dependence on Russian natural gas and oil as his leverage. He's done this with Ukraine using false claims of overdue bills on inflated natual gas prices in violation of the agreements, but after shutting off the pipeline, he's always turned it back on for a reason.

He knows if he actually shuts down the pipeline the EU will revolt against him. That's the certainty he knows about the EU, their dependence but mostly his revenue from the sale of natural gas to the EU. Turning it off stops both, something the Russian economy and government can't survive for very long.

So this is what he's testing, especially Germany and a few other countries who are heavily dependent on Russian natual gas, in short, how long can they survive if the gas is shutoff and what they will do in response and how far will their tolerate his intervention in Ukraine.

Putin is gambling the EU doesn't have the interests to threaten their source of natural gas, but without the sale of it to the EU, Putin and the Russian government is equally hurt, and that's what the EU has to use against him than their fear of consequences.