A third, even larger alliance, established in September, 2012, brings together rebel units affiliated with Muslim Brotherhood style Sunni Islamism. This is the Syrian Islamic Liberation Front. It includes many of the best known fighting groups in Syria — such as the Farouq Brigade, formed in Homs, the Suqour al-Sham group from Idleb and the Tawhid Brigade of Aleppo. It is reckoned to have around 40,000 fighters.
There are myriad local initiatives which pledge allegiance to none of these alliances. But these are the key players.
Current US and Western policy seeks to centralize the flow of (largely Persian Gulf) aid to the rebels through the Supreme Military Council of General Salim Edriss. The US is also offering training to a select group of non-Salafi rebels, on Jordanian soil.
It is vital to understand that there are no large, secular fighting groups engaged on the ground alongside the Islamist alliances mentioned above. Rather, the bulk of the forces nominally aligned with the Western supported Supreme Military Council are those groups noted above as constituting the Syrian Islamic Liberation Front — that is, the Muslim Brotherhood type groups.
An important concern is the possibility that forces aligned with Nusra or the other Salafi groups could deploy on the border with Israel and begin Sunni jihadi attacks against Israel on the Golan Heights. Western policy appears to include a desire to install non-salafi fighters along the borders with Jordan and Israel to prevent this.
So the range of opinion among the fighting groups currently engaged against Assad in Syria stretches from al-Qaeda style Islamism to Muslim Brotherhood style Islamism. Western and Gulf policy is to back the Muslim Brotherhood type units.
This policy is moving ahead. But the level of support still seems far too low to effect a victory for these forces any time soon. Instead, the de facto fragmentation of Syria along ethnic, sectarian and religious lines looks set to continue apace.
In this regard, it is worth noting that there have already been instances of violence between Jabhat al-Nusra and the Muslim Brotherhood type units (specifically the Farouq Brigade.)
In contrast to the government controlled areas and the Kurdish controlled north-east, the rebel-controlled regions remain divided by factional interests. Increased internecine violence between the various strands of the Sunni insurgency is likely in the medium term.
Bottom line: Sunni Islamism is currently at war with Shia Iran and its allies on the territory of what was once Syria. The likely result: either eventual Sunni victory and the birth of a new Sunni Islamist powerhouse on the Mediterranean, or the long-term Balkanization and fragmentation of Syria.