In June 2014, ISIS fighters swept into Mosul, Iraq’s second-largest city, and easily defeated the Iraqi Security Forces, armed with advanced American weaponry but unready or unwilling to engage in close combat against the Salafist militants. The campaign to liberate Mosul from ISIS may be the purest expression yet of twenty-first-century warfare. It was highly politicized, ideologically charged, fought in a fractured state among civilians by a coalition of the willing, with great power involvement on all sides, exposed to the world on social media. The air war, too, represented an intensification of recent operational trends: enhanced command and control measures, universal employment of precision munitions, increased intelligence, surveillance and reconnaissance capabilities, ubiquity of remotely piloted aircraft, and decreased tolerance for civilian casualties. None of these factors was new in 2016, but each of them was manifested over Mosul to a degree not previously seen.