Now, as we enter a new phase in the war in Syria, we have to examine an issue not so obvious in the West: the differences between the two Islamic forces operating there: The Nusra Front that changed its name Fath a-Sham and Daesh – the Islamic State. The difference in names tells us about the difference in nature: while Nusra is about Syria, a-Sham is the original name of Syria before Sykes-Picot agreements, Daesh is about Islam.
There were good reasons why the West got confused: there are so many groups and all are similar in their narratives that it's hard to tell who's who. But what confused everyone, in particular, was the fact that Ayman Zawahiri was recognized by Nusra to be their spiritual leader to provoke the claim of a global caliphate of Abu Bakr Al-Baghdadi, Daesh leader.
Ayman Zawahiri was bin Laden's lieutenant, and naturally the West tagged him as an Al-Qaeda leader, and as a result tried to explain that the Islamic State split from al-Qaeda. Well, not exactly true. Ayman Zawahiri is the Muslim Brotherhood leading figure that operates at present from afar to help Moslem Brothers in Egypt. Bin Laden has appointed him as his deputy in an endeavor to unite the Sunna: Moslem Brothers and the Salafist in one ditch.
There are many differences between these two factions that lead Sunni Islam, but the bottom line would be that while the Muslim Brothers are part of "Political Islam" Namely: ready for dialogue with the West, Daesh, on the contrary is preparing for war on the West.
As things related to Syria: A-Nusra considered itself part of the solution and kept in touch with various Geneva Conventions in search of a solution to the crisis, while Daesh was sworn to fail any solution, and hence while Nusra restricted itself to operate inside the borders of Syria only, Daesh saw itself as a global movement, which Syria is only a launching pad to attack the West and if they lose Syria, they go somewhere else.
Hence, if Nusra perceived themselves as part of the solution, they regarded Daesh as part of the problem. Although the two movements cooperated where they both faced Assad, where Assad didn't exist they fought each other.
What was the formula for the solution for Syria? The various Geneva conventions published long texts of decisions, but the bottom line was that the Moslem Brothers and the Baathists would establish in Damascus a unity Government (without Assad) like the several Palestinian Unity Governments between Hamas and Fatah.
Turkey, being a Moslem Brothers superpower, supported that formula while Russia rejected it. Turkey has supported Nusra since day one and hoped that they would enter Damascus through diplomacy after they has failed on the battlefield. That's precisely why Russia had resisted it- not only they were not ready to talk about the future of Assad as part of the solution, but also not to open the gates of Damascus wide to the Muslim Brotherhood.
Daesh was of course against all these moves altogether, but as far as Daesh was concerned, there was a twist in the plot that is not so familiar to everyone in the West. Those who were behind the creation of Daesh were no other than Assad himself and his Shi'ite ally in Baghdad, Nouri Maliki.
When the Syrian revolt broke out, Assad was confronted with a difficult problem: the world perceived the insurrection as popular anger and a desire of the Syrians to break off the yoke of a tyrant. Assad claimed that these were terrorists and not freedom seekers, and that he was engaged in a war against terror like the rest of the world. But none in the West "bought" it. In this situation, what would he do? Making a terrorist enemy to establish his claim that it was fighting terrorism! And this enemy was Daesh. At a relatively early stage, in a sudden "escape" from prisons in Syria and Iraq Al-Qaeda activists joined forces with military officers of Saddam Hussein's Ba'ath party, formed Daesh and Assad got an "enemy".
But it was "strange" enemy- an enemy that sells oil to Assad. There were battles between the Assad and Daesh, no one can deny it, but it is unclear whether they were actual battles, or they did just the minimal efforts to pretend as engaged in a war. One can question how was it that Palmyra passed from hand to hand without a real fight – at least compared to the furious war in Aleppo.
Daesh played another significant role for Assad, they split the front of the Sunna and foiled the Geneva's formula to bring the Moslem Brothers to Damascus on diplomatic ways. As President Obama explained it in his latest UN address- they spoiled the reputation of Islam as an ally of the West (and as such – disqualified the Moslem Brothers as partners to the solution in Syria.)
Indeed, in examining what is going on in Syria in practical terms, Nusra suffers defeats in Aleppo, while Daesh is gaining strength in Palmyra almost without a fight. In other words: Turkey and the Muslim Brotherhood weakened their position, but far from being thrown out of the equation of solution for Syria, while Daesh got stronger.
In Iraq the situation is different and need a separate review.