Why did Sunni Arab tribes pledge allegiance to Islamic State?

A number of Sunni Arab tribal sheikhs and tribes in Fallujah and Ramadi in Anbar province have pledged allegiance to the Islamic State [IS] militant group. The sheikhs and tribal leaders made the pledge to IS in Fallujah in a statement read out by Ahmed Dara al-Jumaili, an influential and known sheikh, after a meeting… Read More Why did Sunni Arab tribes pledge allegiance to Islamic State?