I suspect who is fighting who at the moment is mostly driven by tactical considerations and just plain physical proximity. ISIS, basically, fights everyone it comes into contact with. If there are rebels between it and Assad, it will fight the rebels. If Assad pushes the rebels back and comes into direct contact with ISIS, it will fight Assad.
I suspect who is fighting who at the moment is mostly driven by tactical considerations and just plain physical proximity. ISIS, basically, fights everyone it comes into contact with. If there are rebels between it and Assad, it will fight the rebels. If Assad pushes the rebels back and comes into direct contact with ISIS, it will fight Assad.