There is rising speculation that a constellation of Iraqi forces will launch an operation to take back Mosul from the Islamic State this fall, supported by U.S. and coalition air power. But a trip made by the author this month to the frontlines around the city suggests such a near-term timetable may be optimistic. While the Islamic State has shown a singularity of purpose in holding onto its caliphate’s second city, there continues to be significant discord and distrust between the many forces and militias arrayed against it. This has slowed progress in even reaching the city periphery, as has fierce resistance put up by the Islamic State in surrounding areas. These dynamics mean that ejecting the terrorist group from Mosul and preventing its return will be an even more challenging task.