As fighting rages in the streets of Syria’s largest city, FRONTLINE journeys to the heart of the insurgency, inside the rebel groups that are waging a brutal, full-scale assault on the forces of President Bashar al Assad. Within “liberated zones” near the city of Aleppo, the rebels not only fight the Syrian Army, but struggle against each other in a bitter rivalry between secular and Islamist fighters. The Battle For Syria is an unprecedented portrait of Syria’s rebel leaders, the toll of the war on civilians and the outlines of a potential struggle for power in post-Assad Syria.