In President Obama's U.N. address, he denounced the prevailing idea that Bashar al-Assad's brutish Syrian dictatorship is acceptable since any realistic alternative would be worse. I wonder, though, how genuinely distressed Obama is by President Putin's military intervention on Assad's behalf.
Spherically speaking, Syria is, after all, in Russia's backyard. To the United States, Syria is essentially a blood moon. Hence Obama has kept a commensurate distance. Let Putin pour Russian resources into Syria. He'll either wound ISIS — a plus for the U.S. — or consume himself in another Afghan folly.
I can't see Obama instructing John Kerry to strenuously protest Putin's intervention in Syria. Obama recognizes, I'd wager, that Putin is, for now, merely playing into Obama's hand.