In September 2014, an international coalition led by the US began a military campaign against ISIS in Iraq and Syria, supported by more than a dozen European and Arab states. Extensive airstrikes have supported the operations of Kurdish and Iraqi ground troops in making strategic gains.A focus on ISIS should not underestimate the unpredictable nature of this conflict: sudden changes in fortune have been a hallmark of the Syrian civil war, and in Iraq the concerted action of Shia militias and the military – not to mention Iranian interests – may yet turn the tide. Moreover, as the development of ISIS shows, jihadi groups can fracture suddenly and dramatically. However, bolstered by state-of-the-art equipment seized from Iraqi bases and resources from oil fields in its territory, by reported extensive assets, and by an Iraqi army that, whatever its current momentum, melted before them in June 2014, ISIS will not be defeated without a hard fight.