There are several different rebel groups. All told, estimates cited by U.S. Secretary of State John Kerry say there are between 70,000 and 100,000 rebel fighters. An organization known as the Supreme Military Council, which formed late last year, now unites many rebel groups. For now, the rebels are working together to achieve a common goal -- toppling al-Assad's government. But if the regime falls, it's anyone's guess what will happen. Here's how one local Jabhat al-Nusra (a group affiliated with al-Qaida) front leader put it to CNN in April: "In the period after the regime falls, our main goal is to create an Islamic state that is ruled by the Koran. It can have civilian institutions, but not democracy. We look at the other Free Syrian Army rebels as one of many groups defending religion, so we support them. In the future, we will handle this differently."