The beating administered last month offered a vivid illustration of the extent to which the Syrian revolution has strayed from its roots as a largely spontaneous uprising against four decades of Assad family rule. After mutating last year into a full-scale war, it is moving toward what appears to be an organized effort to institute Islamic law in areas that have fallen under rebel control.

Building on the reputation they have earned in recent months as the rebellion’s most accomplished fighters, Islamist units are seeking to assert their authority over civilian life, imposing Islamic codes and punishments and administering day-to-day matters such as divorce, marriage and vehicle licensing.

Numerous Islamist groups are involved, representing a wide spectrum of views. But, increasingly, the dominant role is falling to Jabhat al-Nusra, also known as the al-Nusra Front. The group has been designated a terrorist organization by the United States for suspected ties to al-Qaeda but is widely respected by many ordinary Syrians for its battlefield prowess and the assistance it has provided to needy civilians.