11/24/2017 (Fri) 01:41:44
There are outdated estimates of the strength of each faction, see pic related. Getting orders of battle is much harder, though. For the rebels and SDF, we know of individual rebel groups and their coalitions, but not of the internal structure of these groups. An interesting thing is the territory held by each rebel group, which is largely uknown and only becomes apparent when they fight each other.
For the loyalists, the SAA's prewar order or battle is known, but that's not very useful. From the very beginning, political distrust, draft dodging and defections meant only a fraction of it was actually mobilized. The regime resorted to other sources of manpower, and thus the SAA has become just one of the several loyalist forces, together with foreign fighters (Hezbollah, Palestinians, Afghans, Iraqis, Russians and Iranians), local forces (NDF and tribes), private forces (Desert Hawks until their disbandment), sectarian or ideological militias (Ba'ath Brigades, Syrian resistance and the Shi'a and Druze militias) and so on.
There have been attempts to document its wartime order of battle, but they've always rapidly become outdated. But whenever there's a new battle, usually the units present are informed.
As for ISIS, I have no clue. All that's known are some specific rebel groups and tribes that pledged allegiance.