The long, shape-shifting shadow war between the United States and Iran’s Islamic republic has taken a pivotal turn with the death of Qasem Soleimani, an infamous and iconic Iranian military commander, in a U.S. drone strike. By killing the architect of Iran’s expanded influence across the Middle East, the Trump administration has escalated simmering tensions with Tehran from an economic onslaught to an act of war that is likely to instigate a dangerous and unpredictable Iranian backlash.