It has been a week of intense fighting between rival armed groups in northern Syria. They have a common enemy in President Bashar al-Assad, but now Syrian rebels and al-Qaeda-linked fighters are battling each other.
The western-backed Free Syrian Army (FSA) and a number of smaller rebel groups are taking on fighters from the armed group Islamic State of Iraq and the Levant (ISIL).
The al-Qaeda-linked ISIL is led by Abu Bakr al-Baghdadi and has been criticised for the increasing violence in Syria, including civilian deaths, and seizing journalists, aid workers and activists.
Wars fundamentally change societies and Syria is no exception. What started as a political uprising against the Assad regime with aspirations for an open society has basically mutated into all-out war dominated by ultra conservative Islamist forces and al-Qaeda jihadists.
The ISIL has risen to prominence very suddenly and violently. The group was established as an umbrella organisation of Iraqi armed groups in October 2006 under the name 'Islamic State of Iraq.'
It has been responsible for the deaths of thousands of Iraqi civilians as well as members of the Iraqi government and its international allies.
By late 2012, the group was said to have renewed its strength and more than doubled its number of fighters to about 3,000. Some estimates put that number between 3,000 and 5,000 now.
In April 2013, the group changed its name to the 'Islamic State of Iraq and the Levant' and became deeply involved in the Syrian civil war.
Its fighters are mostly active in the northern and eastern provinces of Syria.
"Fighting in the rebel-held North undoubtedly weakens the opposition in its fight against the regime. But in the long term, the opposition may benefit from this battle. Al-Qaeda's presence in Syria has been one of the reasons for the international community's reluctance to militarily support the rebels. And the regime has been able to portray the fight as one against terrorism," says Al Jazeera's Zeina Khodr.
So, what is going on in the war-torn country and what does it mean for the Syrian conflict? What is ISIL's role in the Syrian crisis?
This episode of Inside Syria discusses with guests: Richard Barrett, the former head of the UN's al-Qaeda monitoring team; Fawaz Gerges, a professor of Middle East politics and international relations at the London School of Economics, he is also the author of The Rise and Fall of Al-Qaeda; and Saleh Mubarak; a member of the Syrian National Council and a professor at Qatar University.
"The Syrian people on the ground rank those organisations not necessarily according to the American rankings. People in Syria, and I have spoken to many, many [people], make a big distinction between ISIL and al-Nusra. There seems to be consensus that ISIL is a terrorist group, we don't want it, there is suspicion in how it was created, in how it is financed. And there is a common desire among all Syrians to get rid of them because they are as dictatorial as the Assad regime itself and they want to impose a very,very strict interpretation of Islam on us."
Saleh Mubarakm, a Syrian National Council member