The Islamic State, previously referred to as Isis, is a brutal offshoot of al Qaeda.
It now controls a wide swathe of territory spread across the Iraqi-Syrian border.
The White House has ruled out ground troops in Iraq but says it will use force to stop the advance once the country has a new government.
ITV News correspondent Lewis Vaughan Jones reports on how Iraq is tackling its growing militant problem:
Kurdish Peshmerga fighters have emerged victorious in the battle for Mosul Dam, but the question is - what will their next move be?
An ITV News team at Mosul Dam was with victorious Kurdish Peshmerga fighters at the complex earlier today.
ITV News joined a Kurdish unit fighting Islamist militants near Irbil and found them using tanks from the 1950s and short on ammunition.