Jabhat al-Nusra, like the Lebanse Shi'ite organization, is emerging as a movement that combines uncompromising jihadi ideology with tactical flexibility.
Jabhat al-Nusra, the Islamist group which constitutes al-Qaida's "official franchise" in Syria, this week carried out a successful offensive against Western-backed rebel militias in northern Syria. Key areas were captured.
Islamic State and its activities further east continue to dominate Western media reporting on the war in Syria. But in northwest Syria, Lebanon and the area immediately east of the Golan, it is Nusra which is becoming the main Sunni jihadi force on the ground.
There are significant differences in the praxis of these two movements, despite their near-identical ideological stances.
Islamic State prefers to rule by straightforward terror ... Nusra is no less brutal when it deems it necessary, but follows a different, more sophisticated trajectory.
This requires Nusra to at times cooperate with other Sunni groups (including Islamic State), and at other times fight them.
The assault against rival rebel groups began on Saturday and was mainly focused against the Syria Revolutionaries Front (SRF), led by former construction worker Jamal Ma'arouf. Ma'arouf, who hails from the Jebel Zawiya region of Idlib province, emerged as a successful warlord in one of the heartlands of the Syrian Sunni rebellion.
According to sources in northern Syria, however, Ma'arouf is seen by many as a corrupt figure who has personally enriched himself in the course of the Syrian war.
The tensions between Nusra and SRF in the north are of long standing, and have claimed lives on both sides.
They are concerned with power, and the control of populations, land and resources.
Nusra's forces made rapid progress into Jebel Zawiya, capturing Ma'arouf's home village of Deir Sunbul; the smaller Harakat Hazm militia also abandoned a number of villages in the wake of the group's advance. Nusra is now just a few miles from the Bab al-Hawa border crossing between Syria and Turkey.
Ma'arouf [SRM] was known to have been in contact with Western officials, though the extent of aid to his movement is not clear. Hazm, however – which numbers only around 5,000 fighters – was the recipient of direct Western help, including a number of BGM-71 TO W anti-tank systems delivered this past spring.
These systems may well now be in the hands of the al-Qaida- associated Nusra, following Hazm's abandonment of areas of northern Idlib province in the wake of Nusra's advance against the SRF.
The future of Hazm and SRF in the rebel heartland of northwest Syria now looks uncertain.
Nusra appears uninterested in proclaiming an "Islamic state" of its own any time soon, but it is clearly deeply interested in capturing and holding ground in this area – and is doing so.
Oddly, in other areas, Nusra cooperates with the very forces it fights in the north. In western Syria and the Lebanese Beka'a, for example, Nusra and Islamic State work together in the Qalamun mountains area, and in frequent forays into Lebanon.
There, they seek to secure a link between pro-rebel Sunni towns in the Beka'a and the jihadi fighters in the mountains, so as to ensure a supply route throughout the winter.
Nusra recently killed around 10 Hezbollah fighters in a hitand- run raid on a position near Britel. It also took part, together with Islamic State, in a large-scale raid on the town of Arsal in August, capturing a number of Lebanese soldiers.
Nusra leader Muhammad al-Jowlani issued a statement on Tuesday, promising further incursions into Lebanon.
Addressing Hezbollah directly, Jowlani said,
"The real war in Lebanon is yet to begin, and what is coming is so bitter that [leader] Hassan Nasrallah will bite his fingers in remorse for what he has done to Sunnis."
Further south, Nusra is a key element in the rebel forces that have been enjoying considerable success against the regime in recent weeks. The organization played a major role in the capture of the Quneitra crossing at the end of August.
Some reports have since suggested the organization has ceded control of areas bordering Israel to other rebel forces. But if this is so, it has taken place not by coercion, but because Nusra appears to be aware of the general rebel desire for Western support, and is willing to adjust its own positions accordingly.
The movement also continues to enjoy contact and probably also support from the Emirate of Qatar, a key backer following Nusra's emergence in 2012.
Certainly, the Qatari role in paying ransoms for the release of 45 Fijian soldiers captured by Nusra in the taking of Quneitra would seem to attest to, at the very least, ongoing contact between Doha and the jihadis.
So in three key fronts – Idlib province, Qalamun and Quneitra/Deraa – Nusra is playing a pivotal role, challenging both Syrian President Bashar Assad's army and other rebels where it deems it profitable.
By avoiding targeting Westerners, the group has largely managed to avoid the hostile attention of the West.
By adjusting its activities to local realities and power structures rather than immediately challenging them head-on, it has also avoided the fear and hostility which Islamic State engenders among many Sunnis in both Syria and Lebanon.
So what happens next? Jowlani clearly has his eye on Lebanon, where 1.5 million Sunni refugees from Syria may provide willing recruits to the movement, particularly if that group begins to find itself needing some kind of sectarian defense against local Shi'ite hostility. Nusra is becoming the controller of rebel northwest Syria – yet it is likely to continue its more cautious path in the south, where its rivals are stronger.
It is also by no means impossible that Nusra could, at a certain point, turn its attention to Israel. Certainly, the current attempt by Palestinian organizations to refocus attention on their struggle through the prism of Pan-Islamic concerns for the Aksa Mosque makes such an outcome more likely.
Jabhat al-Nusra seems determined to emerge as a kind of mirror image of the Shi'ite Hezbollah – combining an uncompromising jihadi ideology with tactical flexibility and an ability to work with its own public (Sunnis), rather than simply terrorize them into submission.
Israeli and Western governments should be watching the organization very carefully.
*Jonathan Spyer is director of the Global Research in International Affairs (GLORIA) Center and a fellow at the Middle East Forum.