In Iraq’s Sunni dominant North West, ISIS has made rapid gains while only fielding a combat force estimated at between 6,000 and 10,000 soldiers. It’s not surprising that local Sunnis haven’t put up much of a fight given the rough treatment they’ve received from the Shia dominated al-Maliki administration in Baghdad. Why would they fight against fellow Sunnis for a government that treats them as second class citizens?
But as ISIS attempts to break out of its ethnic and religious home territory, it might meet stiffer resistance. To the North East the Kurdish peshmerga forces number in the hundreds of thousands. While the Kurds are Sunni dominant, they have been fighting for an ethnic homeland since the modern division of nations in the Middle East, and they won’t be keen on trading one set of Arab overlords for another. To the South East, ISIS faces the bulk of Iraq’s Shia population, which enjoys the backing and support of neighboring Iran, and the U.S. A reorganized Iraqi military, with the help of Shia militias like the Mahdi Army led by Muqtada al-Sadr, will make advances in the South East difficult for ISIS’s small fighting force.
On the other hand, ISIS is well funded with money looted from banks in the north and donated by wealthy Arab Sunni benefactors. The polished ISIS propaganda machine has also been able to attract jihadi reinforcements from around the globe. It’s also possible greater numbers of local Sunnis will find that they enjoy life out from under the thumb of the Shia government and join ISIS, turning the conflict into a separatist sectarian civil war. It remains to be seen what level of success ISIS can muster in territories outside its Sunni comfort-zone.