ISIS beats up the rebels. We beat up ISIS. He tells everyone we're covertly on his side = WIN.
For Bashar Al Assad the ideal scenario is one in which ISIS helps him kill off his armed nationalist opposition in western Syria, American aviation assets pound ISIS positions in the east, and he sits comfortably in Damascus, feeling once again needed by the West as a useful partner against those arguably more evil than him. And a lucrative dividend awaits: The fact or perception of collaboration between Washington and Damascus driving wedges between the U.S. and every one of its regional partners, thereby serving the interests of the party Assad has so faithfully served: Iran.
Based on his experience with Washington since mid-2011, Assad has every reason to believe his strategy will bear fruit. Now, as his own forces focus on bombing, shelling, and starving civilians, ISIS fighters in western Syria work obligingly to eliminate his armed opposition. Now, as the U.S. contemplates an aerial campaign against ISIS targets in the east, Assad envisions a continuation of living large at the expense of others: Iran, Russia, ISIS, and now America. He expects harsh rhetoric from Washington. He will tell allies and adversaries alike to pay no attention to the words of those who have told him to step aside, warned him of red lines, threatened him with military strikes, and promised aid to opponents that never quite materialized in the forms or quantities required.
Indeed, if all the administration has to offer is more rhetoric, it is walking into a deadly geopolitical ambush. Even as Washingtonideally joined by partnersgoes its own way operationally against ISIS with no reference whatsoever to the Assad regime, Assad will be believed both inside Syria and around the region when he claims that the fix is in. He will allege coordination and collaboration when none exists. He will hint at prominent visitors from Europe and the U.S., irrespective of their actual authorities. If all there is from Washington is talk, he will be believed.
http://www.newrepublic.com/article/119226/us-airstrikes-isis-syria-are-not-enough-punish-assad-too