BEIRUT When an explosion killed almost all of its leaders in a single blow last year, many thought it was the end for Ahrar al-Sham, a powerful Syrian insurgent group founded by members loyal to al Qaeda.
But the group immediately re-emerged stronger. It replaced its leader and chose new military commanders. A few months later, it joined a coalition of insurgent groups that seized the city of Idlib with at least 2,000 fighters, making it the most influential group in the Fatah Army (Army of Conquest), which includes al Qaeda's Syria wing, the Nusra Front.
The group now has even loftier ambitions.
With strong backing from Syria's neighbor Turkey, Ahrar al-Sham (the Free Men of Syria) is playing a significant role in Syria's four year old civil war - if not the biggest among insurgent group apart from Islamic State.
Its fighters control Bab al-Hawa, the only legal crossing between Turkey and Syria's rebel-held areas, and are powerful around Aleppo and Idlib.
The emergence of strong rebel groups such as Ahrar al-Sham which have political representation as well as military strength could help address a long-standing criticism of the opposition to President Bashar al-Assad: the disconnect between the constellation of armed groups in Syria and the Turkey-based political coalition that does not speak for any of them.
A western diplomat said that Ahrar al-Sham is seen as a decentralized, pragmatic group that is willing to work with other groups, and it will most likely have a say in any future peace talks.
While its late leadership showed no interest in the idea of ruling, Ahrar al-Sham's current command appears to want a part in any long-term solution in Syria.
It is already negotiating with Assad's government and its Lebanese ally Hezbollah over the fate of a rebel-held town near the border with Lebanon and two government-held Shi'ite towns under rebel siege in northwest province Idlib.
The talks, which have collapsed at least twice, are backed by Turkey and Iran, regional heavyweights on opposite sides of the conflict. They have given Ahrar al-Sham the advantage of negotiation experience in any future talks to find an end to the war.
They have also demonstrated Ahrar al-Sham's standing among rebel groups, who have respected the ceasefire agreements it negotiated. That includes Nusra Front.
"Ahrar al-Sham is now a nucleus of a state," said one of the group's commanders, giving an interview to Reuters over the Internet on condition he not be identified. "Ahrar has a strong foundation, it consists of scientific and academic cadres that are not present in all of other Syria's groups together."
"The fact that the movement overcame the assassination of all its first line leaders quickly and had a strong comeback, shows that it is an institutional movement," the commander added.
No one has claimed responsibility for the blast that killed the group's leaders.
Since then, it has set up offices that deal with politics and military, religious, social and financial matters. Each bureau is independent but reports to a higher command.
"We as a movement still believe that one of the ways to achieve change is through arms. We cooperate with all groups on all fronts," the commander said.
Despite its origins as an ally of al Qaeda, Ahrar al-Sham plays down any commitment to global jihad and emphasizes its national credentials as a Syrian movement that respects the country’s borders. It says its fight is limited to the Syrian front.
Such a position would come as a relief to Western countries worried about jihad spreading to Europe and elsewhere.
Aware of the West's growing fear of the influence and strength of hardline jihadist groups inside Syria, Ahrar al-Sham has published editorials in two Western newspapers, distancing itself from hardliners and saying it would protect religious minorities.
It also opposes the ultra-hardline group Islamic State.
When it was formed, it had strong ties with the leadership of al Qaeda. Its slain top commander Abu Khaled al-Soury fought alongside al Qaeda founder Osama bin Laden and was close to bin Laden's successor Ayman al-Zawahiri.
Since the deaths of its leadership, it had an interim leader until last week, when it finally selected Abu Yahya al-Hamawi as new permanent leader. A civil engineer and veteran militant in his 30s, the new leader reached out to other rebel groups in his first message, promising they would be included in any deal his group strikes.
"We will all be partners in the decision and in the execution of it," he said on his Twitter account.
Due to its strong relationship to Turkey and its decision to take part in talks with the Syrian government, it has sometimes come under criticism from other rebel groups.
Under its new leadership it is trying to differentiate itself from al Qaeda, angering the Nusra Front and other hardliners. But its al Qaeda-linked background means Ahrar al-Sham still has a special relationship with the Nusra Front.
Rebels inside Syria say Ahrar al-Sham supplied many of Nusra's weapons. It was not clear if it was still doing so.
A former Nusra fighter who has now left the war said Nusra and Ahrar once had strong relations.
"All I know is that Nusra sees Ahrar as their source for weapons, especially in some battles," he said. "They are moving away from military work and putting their strength in administrating liberated areas."
"Their strength is evident in running the Bab al-Hawa crossing. They control it after kicking everyone else out and hence they control the trade in and out of Syria, putting the transfer of goods to all Syria under their control. They have become self-funded after imposing taxes on goods coming into Syria," he said.
It is not only other rebel groups that are keeping a close eye on Ahrar al-Sham's rise - its enemies are equally watchful.
"We have noticed they are trying to distance themselves from Qaeda but they remain Salafis, this can not be denied," said a military commander on the Syrian government side who is also close to negotiations with the group. Salafis are followers of the austere form of Sunni Islam preached by al Qaeda.
"Unlike most Syrian insurgents, they do have a structure and their fighters are loyal to the leadership and effectively implement its orders."
(Reporting by Mariam Karouny; Editing by Peter Graff)