THE PERFECT WAR:

Russia's motivation is simple: to protect Assad. Putin believes he is defending a basic principle against "outside intervention" that seeks to bring down an allied government--as he's angrily watched happen over the last 15 years in Serbia, Iraq, Libya and Ukraine. And Russia's military role in the Syrian conflict is hardly new. They've been there from the beginning as one of Assad's only allies and chief weapons suppliers. Russian personnel have been on the ground throughout.

Seen this way, Putin's moves are driven primarily out of fear and weakness, not confidence and strength. He sees his only ally left in the region on the ropes and therefore Russia had to come to his defense. Russia wants to maintain the only military outpost it has in the region, anchored by a key naval facility in Tartus.

Now that Russia has decided to go all-in to back Assad, it will have to be there for the long haul. It may enjoy some tactical battlefield successes. But defeats and mistakes are just as likely (or, as shown by Russian missiles landing in Iran, perhaps more likely). And for Russia to maintain its position it will require a continuing supply of resources and higher costs, which will prove harder to sustain over time.

Putin also wants to use the military intervention in Syria to change the subject from some of his troubles at home, particularly the situation in Ukraine and Russia's economic tailspin. 

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