My answer to Why hasn't President Obama degraded and ultimately destroyed ISIS or “ISIL” as he calls them as promis…
Answer by Abbey Laurel-Smith:
Because the main core of ISIS are run away ex-Russian soldiers, ex-Georgian servicemen that we trained, and ex-European and Turkish soldiers, plus Iraqi revolutionary guards. They know our tactics. They know how to fight, when and where to fight and are well organized with their operations. They know how and when to move.
Worse for us, they have an unpredictable organizational structure that works well for them. They are constantly spying and gathering info on us. While we have to be careful not to expose ourselves too much.
Russia wanted them all dead at all cost. We are being careful because some funky allies are also working the other side.