A decentralized collection of groups fighting the al-Assad regime and various militant groups, the Free Syrian Army was founded in the summer of 2011 by a group of defectors from the Syrian military. While there was an early attempt to establish centralized command of the group, this has since collapse and the FSA now is essentially made up of a series of smaller organizations which identify with the FSA brand. The members of the FSA have attempted to cast themselves as the leaders of the moderate Syrian opposition, but they struggled to gain authority over the many other disparate groups fighting in the conflict.
Some estimates (Omran Dirasat and Al Jazeeza Centre for Studies) in late 2015 put the number of FSA affiliated fighters at roughly 35,000. They arrive at these estimates by adding up the totals up each group which claims to be part of the fragmented FSA.
The FSA has received varying levels of support from states such as the US, the UK, Turkey, Qatar, Jordan, and Saudi Arabia.
The Southern Front was established in February of 2014.
The United States, United Kingdom, Saudi Arabia, the United Arab Emirates, Turkey, and Jordan have provided support to the Southern Front. This is organized through the Military Operations Center (MOC), which is run out of Jordan and Turkey.
The UK House of Commons (Sept. 2016) estimated the Southern Front's size at approximately 25,000 fighters.
According to the Christian Science Monitor (Nov. 2016), the Southern Front has roughly 30,000 fighters active in Syria.