In September 2017, U.S. official Brett McGurk expressed concern that Syria’s northwest Idlib province had become “the largest Al Qaeda safe haven since 9/11.” Idlib had fallen to al-Qaeda, in the form of a jihadist coalition led by the group’s Syrian affiliate, the Nusra Front, in March 2015. Despite acknowledging that Idlib, the last bastion of the supposedly democratic and secular Syrian opposition, was dominated by al-Qaeda, McGurk failed to also note that U.S. planners themselves had played a key role in the terror group’s successful capture of the province. Specifically, he failed to...