Syria remains rocked by antiregime protests that have endured since March, and the country may be headed for civil war. That's because unlike in Egypt or Tunisia, sectarian rivalries are central to Syrian politics. That adds an element of danger to the situation—but also points the way toward how dictator Bashar al-Assad may fall, especially if the West takes the proper initiative.

Syria's population is 74% Sunni Muslim. Yet the Assad regime is Alawite, an offshoot of Shiite...