i read up on it a little and part of the reason why isis became so popular/such a threat was due to the disbanding of the iraqi army, american trained and funded, after the goverment was toppled and our top brass didn't need them anymore or something. this made thousands of men with military angry with america for abandoning them n stuff. the leader of isis used the revolt in syria to recruit more angry people i think. i might be talking out my ass but idk.