My personal opinion is, Syria - Iraq (current Shiah government) - Iran there's a big Muslim Shiah Region inside the Middle East. Someone dislike this pro-Shiah situation, and release ISIS beast try to separate above Shiah region inside Iraq.
What current Iraq government really need is a military advisory group, to train Iraq soldiers how to deal with guerrilla warfare & urban combat.
It's happened to China PLA ever supported Sri Lanka Army to finish their Tamil Tiger rebel force, spent two combat years to end half of century problem at the North island. As far as i knew China sent PLA military advisors under the table and China weapons arm Sri Lanka Army to win the War. China provided military advice and arms to exchange Sri Lanka's mineral and seaport, it's a Secret War !
Good analysis ! Iraq soldier need well trained to face guerrilla warfare.