THE PRO-ASSAD FORCES
The regime of Bashar Al-Assad is supported internationally by Russia and Iran. Operatives on the ground include the Syrian government army, various militias linked to the President and the militias of Hezbollah and other Shiite groups. Russia, which holds the key Syrian port of Tartus, the only access on the Mediterranean for the Russian fleet, has so far mainly struck rebel occupied areas, particularly the region of Idlib, recently conquered by the coalition formed by the al-Nusra Front and Ahrar al-Sham.
The Syrian army
Regime forces are concentrated along a line that runs from South to North and they control territories overlooking Lebanon and the Mediterranean Sea, including the cities of Damascus, Homs, Hama and Latakia.
In recent months, different sources have emphasized the weakness of the Syrian army, now reduced to half of its original force (300,000 men) and limited by an increasingly substantial presence of conscripts. The Syrian President has managed to resolve some of these critical issues by deploying irregular militias (the infamous National Defence Forces) and, above all, with the support of external forces, such as Hezbollah.
Operating in support of Assad are other little known groups of Sunni, Alawite, Kurdish and Christian extraction. Groups of note include Muqawama Suriya, the Liwa Dir al-Sahel and Dir al-Watan.
Hezbollah is the main Shiite militia engaged in Syria. It justifies its intervention as a defensive jihad to protect the sanctuary of Sayyida Zaynab in Damascus and to fight the Takfiris, Sunni extremist groups who accuse "deviant" Muslims, and Shiites in particular, of being unbelievers. Supported by Iran, it coordinates other Shiite groups in the area, including other Iraqi and even Pakistani contingency forces. Hezbollah operates mainly in the areas bordering Lebanon From Qalamoun to Homs.
THE ANTI-ASSAD FORCES
From an international perspective, the main forces that are working to topple Assad are Saudi Arabia, Turkey, Qatar and the United States. On the ground, they are supporting multiple forces that differ both from a tactical, strategical and ideological-political standpoint. Saudi Arabia is the largest supplier of military and financial support to various rebel groups, particularly the Salafists. United States provide military assistance to several rebel groups, including even Islamist and Jihadist groups. The CIA launched a training programme aimed at 5,000 anti-Assad rebels, which ultimately failed.
Jabhat al-Nusra Front
Out of the groups that are not affiliated with ISIS, the best known movement is undoubtedly the al-Nusra Front. A Syrian offshoot of al-Qaida, it operates in the region of Idlib along the corridor separating Hama and Homs, near Damascus and on the Southern front, especially on the Golan Heights. They are supported and financed by Turkey, Saudi Arabia and by other Gulf state countries.
Less well-known than the al-Nusra front, Ahrar al-Sham is perhaps the most significant opposition movement in terms of military forces and popular participation. Salafi-inspired, they are trying to overthrow the Assad regime to establish a state based on Sharia law, so much so that from an ideological standpoint it is hard to distinguish them from the al-Nusra Front, even if unlike the al-Nusra Front the United States does not consider them a terrorist organization. They operate in the areas of Aleppo, Idlib, Homs and Hama. In 2012, Ahrar al-Sham created the Syrian Islamic Front, a group that brought together several allied militias, including Jaysh al-Islam, a force mainly operating in Damascus, and Liwa al-Tawhid, engaged mainly in Aleppo. They are supported financially by the Gulf States.
Jabhat Ansar al-Din
A jihadist coalition operating mainly in Northern Syria, independent of other groups such as ISIS, Jabhat al-Nusra or Ahrar al-Sham. It is formed of Harakat Fajr al-Sham and Harakat Sham al-Islam. Originally, Jaysh al-Muhajirin wa-l-Ansar was also part of the group, providing the coalition with some more conspicuous contingents, but they recently seconded to join the al-Nusra Front. Before this split, Jaysh al-Muhajirin was connected to the Emirate of the Caucasus by its leader Salah al-Din al-Shisani, and mainly consisted of Caucasian fighters. Now it is mainly formed of Arab militants and led by a Saudi.
Free Syrian Army
The armed wing of the Revolution at the beginning of the Syrian uprising. It is formed of groups of exclusively Syrian extraction and particularly of defectors from the government army. As it is not classified as an extremist group, it receives international funding, but it is difficult to assess its effective operational capacity.
The operations rooms
Because of the complexity and heterogeneity of the combatant groups reality, the opposition front has sought to create "operations rooms" in order to bring together different groups in specific fronts, united by their opposition to the Assad regime. These operational synergies also emerged with an anti-ISIS purpose, as shown in the North-West of Syria in December 2013 when the forces of various groups merged into the "Islamic Army" (Jaysh al-Islam) and managed to inflict heavy losses on the Caliphate's forces. Along these lines, it is also interesting to recall the creation of the "Army of Conquest" (Jaish al-Fatah), thanks to which different groups have joined in coalition, particularly Jabhat al-Nusra and Ahrar al-Sham, succeeding in creating and maintaining an area of influence within the backdrop of Idlib.
The Kurdish PYD
Finally, there are two other important groups active in the Syrian civil war that differ from previous groups for specific ideological and strategic positions: the military wing of the PYD (Democratic Union Party, and according to some the direct offshoot of the PKK) and ISIS. With regard to the first group, the Kurdish forces have distinguished themselves on the ground, by managing to block the advance of ISIS in January 2015 in Kobane, and they still control two large pockets in northern Syria with the ultimate goal of unifying the entire region of Rojava.
Finally, active in Syria since winter 2013, the forces of ISIS have their focal point in the city of Raqqa. While ISIS may be compared to a state with borders and a well-defined territory, its presence in Syria extends along strategic corridors, that allow for connections with occupied Iraqi cities (Ramadi and Mosul in particular) and with other Syrian areas under its control (including Palmyra and, in part, Deir ez-Zor) or attack, including Aleppo and Damascus.