A plume of smoke rises after a rocket fired by a Syrian regime jetfighter impacts in the Sheikh Maqsood neighborhood of Aleppo.
For nearly two years after the Syrian uprising began, in March 2011, Barack Obama managed to keep his distance from an Arab Spring revolution that seemed to promise him only trouble. The White House feared entanglement in another Iraq-style sectarian bloodbath and wasn't sure that whoever might replace Syrian dictator Bashar Assad would be an improvement. Now Syria has become impossible for Obama to ignore. That's partly because of a horrific death toll that has climbed past 70,000. But arguably more significant for the White House is the growing fear that Assad's huge chemical-weapons arsenal poses a threat beyond...
