Five years ago, during the optimistically named Arab Spring, Syrians staged peaceful protests against the ruling dynasty that had long oppressed them. President Bashar Assad responded brutally: In May 2011, he sent tanks into the suburbs of Damascus, Deraa, Homs and other cities to crush his critics. Civil war followed.
Experts, not least those in the U.S. government, convinced themselves that the rebels would prevail. There were simply too many angry Syrian Sunnis and Mr. Assad, a member of the Alawite minority, had too few loyal troops. Before long, Sunni jihadis from abroad began streaming into Syria to support the rebels. Among them were branches of al Qaeda, one of which splintered into the Islamic State.