 It has been a decade now since the Islamic State terrorist group declared a caliphate in large parts of Iraq and Syria. BBC's Frank Gardner. The nearly five years of rule by the so-called Islamic State, inflicted on millions of citizens in Iraq and Syria, will be remembered for its extreme brutality. It targeted Christians, Shia Muslims, ethnic Yazidis, policemen and their families. Anyone, in fact, who opposed its narrow and violent version of Sharia, Islamic law.