For a limited deployment of 2,000 soldiers and some weapons, Mr. Putin is showing Russians their country has global influence again. He needn’t waste Russian blood because Hezbollah provides the cannon fodder. And he needn’t defeat Islamic State as long as he carves out an Alawite protectorate around Damascus and Syria’s coast. Mr. Assad needs Islamic State as an enemy for now because he can pose as the lesser evil. His goal—and the Kremlin’s—is to slowly win Western agreement that Mr. Assad is necessary for Syrian stability.

Mr. Putin is also showing that Russia is an ally to be trusted, in contrast to an America that abandoned Iraq in 2011 and won’t fight ISIS with conviction. His alliance with Iran gives him leverage throughout the Middle East, and his Syria play may even give him leverage with Europe over Ukraine sanctions. Perhaps he’ll offer to limit the barrel bombs that have sent refugees fleeing in return for Europe easing sanctions. Some quagmire.

Mr. Obama could make Mr. Putin pay a price if he reversed his Middle East policy and revived American leadership. In Syria the U.S. could set up a no-fly zone to create a haven for refugees against Islamic State and Mr. Assad’s barrel bombs. He could say U.S. planes will fly wherever they want, and if one is attacked the U.S. will respond in kind.