For the past several months rebel groups aligned with ISIS in Aleppo province have spent nearly as much energy battling factions serving under the umbrella of the Western-leaning Free Syrian Army (FSA) as they have fighting the regime of Syrian President Bashar Assad. According to al-Quds al-Arabi, an Arabic-language newspaper published out of London, the media office of ISIS issued a statement on Sept. 12 saying it had launched a military campaign against FSA battalions in Aleppo province in response to a previous attack on the ISIS headquarters there. The most recent clashes, which took place in Bab, a district 25 km from the provincial capital, were sparked by an anti-ISIS rally. Enraged, members of the fundamentalist group shot into the crowd, injuring eight, says Abu Mohammad, an engineer who was at the scene…

But as any recently divorced couple knows, untangling assets can be messy. ISIS groups and FSA brigades may be at one another’s throats in Aleppo, but in Maaloula, a strategic town near Damascus, Jabhat al-Nusra worked seamlessly with FSA member brigades to achieve a decisive victory against the regime last weekend. The joint effort raises questions of just how possible it really is to cleave the pro-Western rebels away from the rest

Maaloula is the rule and Bab is the exception, according to Swedish analyst and researcher Aron Lund, who has just completed a study of Syria’s nonstate actors. It is very rare that one group pulls off an operation all by itself. Instead individual commanders from across the ideological spectrum join forces to plan the attack, each contributing its specific expertise and weapons cache. “It’s unrealistic to expect that you can tell rebels to stay away from other rebels as long as civil war is going on.” Al-Nusra, he points out, has a particularly effective battlefield weapon that few of the more moderate groups can claim: suicide bombers. The conquest of Maaloula started with a suicide attack by an al-Nusra fighter on the government checkpoint. The fight went downhill from there. “The suicide attack is a powerful weapon,” says Lund. “Many battles start with an operation to take the military base. To do that you have to break the perimeter, and you can’t do that without a suicide bomber. So that is what Nusra brings to the table.”