Daesh, the Islamic State terrorist army, is the same - yet curiously different - as other "independent" Islamo-Arab terrorist groups. For one thing, it has been backed by Iran, Syria, and terrorist allies in Iraq - several Saddam Hussein officers constitute ISIS' leadership core. It fought alongside Al Qaida - itself a state-sanctioned mercenary army - yet internal leadership squabbles - common to Islamo-Arab terror states - led to a breach. And the group known as Daesh/ISIS is trying to seize and consolidate territory, and Barack Obama's appeasement has whetted its aggression.
UPDATE, November 25, 2015:This piece examines that Iran is not possibly an ally in defeating Daesh/ISIS.