Thousands of Syrian militants have taken control of most of Aleppo, the country's largest city, and its airport, before expanding their offensive to a nearby province. The insurgents faced little resistance from government troops and claimed to have entered the city of Hama. The offensive is a major embarrassment for President Bashar Assad and raises questions about the preparedness of his armed forces. The swift and surprise offensive comes at a time when Assad's allies are preoccupied with their own conflicts. The return of the insurgents to Aleppo threatens to reignite the country's civil war.