The Islamic State of Iraq and al-Sham (ISIS) is starting to show some wear and tear. True, it pulled off the gruesome execution of Jordanian pilot Moaz al-Kasasbeh; true, it has attracted jihadists from across the world; and true, it still holds swaths of Iraq and Syria. But cracks are appearing in the self-styled Caliphate.
One reason is that, starting in the late summer, the U.S. intervention in Iraq helped stall the ISIS advance. Since then, troops have been able to go on the offensive and start expelling the terrorist group from the territory it holds; it has already lost Kobani, the north Syrian border town where much of the violence is centered, and has also suffered significant defeats in Bajyi, Jurf al-Sakhar, Diyala, and the Mosul Dam. In the grand scheme of things, this does not translate into much: Of the 55,000 square kilometres of territory ISIS controls, it has lost only 700—around one percent. But at least the momentum has been checked.
Now, a planned spring offensive, a joint U.S.-Iraqi effort to retake the Sunni capital of Mosul, could be a watershed moment. Iraqi Security Forces, Kurdish Peshmerga troops, and Sunni tribes—backed by U.S. air support and military advisers—will look to end ISIS’ reign in the north and west Iraq, restoring government leadership in local towns and cities.
There are risks in this strategy. ISIS finds it easiest to take over Sunni areas where there is a looming threat of Shia or Pershmerga involvement. To retake Mosul, then, the coalition will have to avoid sending Peshmerga and Shia militias into the fray. The further these forces penetrate the Sunni enclave of Mosul, the likelier they are to push Sunnis into armed resistance.
Absent any Shia or Pershmerga threat to exploit, ISIS quickly loses tactical alliances, such as the Ansar al-Sunna, Army of the Men of the Naqshbandiyah Order (JRTN), and the 1920 Revolutionary Brigades. And when it fights alone, it loses. For example, ISIS had