Here is a link to a well organized and concise description of the different actors present in the ongoing Syrian conflict, from War on the Rocks. If you would like a good primer, it is worth your time to read. Keeping up with the news reports and ever-changing developments is difficult.
Here is the general outline, with a brief excerpt from each section:
Russia happily incurs international opprobrium for backing Assad so that it can preserve access to its last remote naval base in Tartus, which remains a symbol of Russia’s global reach; discourage external interference in a country’s internal affairs; and, most importantly, remain a counterweight to U.S. hegemony in the Middle East.
With chemical weapons off the table, Assad’s external opposition in disarray, Islamists dominating the insurgency, and an American public unhappy with foreign wars, the Obama administration feels it has few options other than taking steps to prevent the civil war from destabilizing Syria’s neighbors and harming U.S. security.
Turkey, Qatar, and Saudi Arabia:
Assad’s three greatest regional foes—Turkey, Qatar, and Saudi Arabia—are divided according to their taste in proxies. Saudi Arabia favors more nationalist-minded groups, perhaps because members of the Muslim Brotherhood in the 1990s and the jihadis in the 2000s challenged the royal family’s rule.
Qatar and Turkey have worked together to bolster the Syrian Muslim Brotherhood’s sway over the external opposition, which has waned despite the two countries’ best efforts. On the battlefield, Turkey appears to have turned a blind eye to Sunni jihadis gaining access to northern Syria while Qatar is widely alleged to have supported conservative Salafi Islamist militias united under the Islamic Front.
Iran has demonstrated the seriousness of its commitment to sustaining the Assad regime by helping provide cut-price fuel and weapons and deploying members of its armed forces, including the special Quds Force, to train Syrian paramilitaries and coordinate military operations against the rebels.
The Syrian government is militarily and politically stronger than its opponents. The U.S. reversal in September 2013 of its threat of punitive strikes in favor of the signing of an agreement to remove and destroy Syria’s chemical weapons stockpiles awarded President Assad diplomatic leverage to play for time and stymie a peace accord. Unless the balance of power changes, Assad will continue to be defended on the international stage by Russia and draw military and financial sustenance from Iran. With such an advantageous position, the regime’s delegation at Geneva played it slow to ensure the opposition got little of any benefit from attending.
An assessment of the Syrian military’s performance in 2012 revealed that the Syrian Arab Army lacked the numerical and command capacity to sustain effective operations in multiple domestic theaters. Beginning in mid-to-late 2012, the SAA—with apparent training and coordinating assistance from the Iran’s Revolutionary Guard Corps—began merging existing “popular committee” local protection militias into an organized, trained, and salaried paramilitary force, the National Defense Force (NDF). Since then, the NDF has become a critical part of the Syrian military structure, usually used to hold seized ground and to bolster coordinated offensives.
The Syrian National Coalition (SNC) is the main body representing various factions of the Syrian opposition outside Syria. Internal infighting between rival groups has structurally weakened the organization. The infighting came to a head on 18 January 2014 when a third of its members boycotted a vote to attend the Geneva II talks. One of the SNC’s main components, the Brotherhood-dominated Syrian National Council, withdrew from the coalition as a consequence. The infighting is a result of conflicts among the factions’ regional backers or irreconcilable differences over the future of Syria.
Free Syrian Army / Supreme Military Council
The FSA has not represented a distinct military organization for a long time now. Today, the FSA name represents more of a brand or umbrella with which primarily nationalist and often secular groups associate themselves. The SMC, meanwhile, presents itself as a coherent structure with organized local, provincial, and national components led externally by Selim Idriss. The command structure, however, has not proven itself nationally and Idriss has been more of a distributor of military aid than a commander.
The Islamic Front represents the singly most powerful opposition military organization in Syria, with an estimated 50,000-60,000 fighters operating in 13 of Syria’s 14 governorates. The IF’s political charter calls for an Islamic state in Syria governed by sharia law, but is vague regarding the specifics of what this would actually entail. While all seven constituent groups within the IF are certainly Islamist, they in fact represent a relatively broad spectrum.
Despite its admitted links to Al-Qaeda, JN has since mid-to-late 2012 demonstrated a remarkable level of pragmatism in religious, political, and military matters. Its military forces consistently demonstrate levels of professionalism and effective command and control superior to that of comparatively moderate groups. While JN represents a numerically smaller organization than most members of the IF, its fighters often represent something more akin to special forces, taking a key frontline role in offensive operations. Because the group fights effectively and does not seek to dominate the opposition, it has healthy relations with all Syrian rebel groups from moderate to Salafist. JN’s widespread provision of social services to the civilian population through its Qism al-Aghatha (or Department of Relief) and avoidance of incurring civilian casualties in areas hostile to Assad has meant the group enjoys a surprising level of popular support.
Islamic State in Iraq and al-Sham (ISIS):
Since its emergence as an active armed entity in Syria in late April/early May 2013, the Islamic State in Iraq and al-Sham focused on acquiring and consolidating territorial control in eastern and northern Syria, particularly in regions bordering Iraq and Turkey. As this proceeded, ISIS began establishing outposts further into Syria’s interior in Hama, Homs, and areas of the Damascus countryside, most notably in the Qalamoun and in Eastern Ghouta. As its influence expanded and confidence rose, ISIS began imposing its harsh behavioral codes and kidnapped, imprisoned, and sometimes executed its opponents. Public beheadings became common, as most importantly, did incidents of ISIS violence against other rebel groups.
The only two major players the article does not describe are Israel, as a state, and Christians, as an element of the population. This is likely because the article focuses on those actively participating in the struggle. Israel, apparently, is taking a wait and see approach. Christians, meanwhile, are understood to be pro-Assad historically, are sometimes besieged by Islamist elements, but are generally keeping quiet, careful not to be seen taking sides.
Of course, those following the conflict closely will likely take offense at some of the descriptions above. For those generally bewildered, however, I trust this summary is helpful.