Syrian Armed Forces
Before the rebellion and war began, Syrian Armed Forces was guestimated at 325,000 regular troops. 220,000 of them were army troops and the rest was part of the navy and air forces. In addition there were nearly 280,000–300,000 reservists.
Since the first protest in June 2011 many defections of government fighters have been reported. By July 2012, the Syrian Observatory for Human Rights (SOHR) and turkish sources estimated that thousands of soldiers had defected.
National Defense Forces
The Syrian NDF was formed out of pro-government militias. They get their salaries and their military gear from the government and number almost 100,000 troops. The units of the NDF act in an infantry role, directly battling rebels forces on the ground and leading counter-insurgency operations. This operations are coordinated with the syrian arab army who provides them with logistical and artillery support.
Hezbollah involvement in the Syrian Civil War has been significant almost since the start of armed rebellion in late 2011. The involvement turned into active aid and soldier stationing since 2012. By 2014, Hezbollah involvement was stable and firm in support of the Assad government forces in Syria. Hezbollah deployed thousands of fighters in Syria and by 2015 lost nearly 2000 fighters. 5000 soldiers were injured in its support to the Syrian government side.