Insurgents breached Syria ’s second-largest city, Aleppo, after blowing up two car bombs Friday and were clashing with government forces on the city’s western edge, according to a Syria war monitor and fighters.

The fighting is a significant escalation since rebels launched a surprise offensive earlier this week, seizing towns and villages as they cut a path toward Syria’s second-largest city.

Former U.S. Ambassador to Syria, Robert Ford, explains what the latest breach by insurgents into Syria's second-largest city Aleppo means for the ongoing Syrian civil war.