With all eyes on the Battle of Mosul, fewer observers of the war against ISIL are paying attention to a major anti-ISIL offensive underway in Syria that may soon reach a crescendo. With the capture of the town of Dabiq from ISIL in northern Aleppo, Turkish-backed Syrian rebels taking part in Turkey’s Operation Euphrates Shield have secured a 20-kilometer deep Syrian buffer zone along the Turkish border.

This is a major development in the wide-ranging Syrian war that offers Turkey two immediate benefits: ISIL won’t be able to lob rockets across the border towards the Turkish province of Kilis and ISIL fighters can no longer easily cross the border, making it harder for them to conduct attacks in Turkey and supply themselves from Turkish territory.

This buffer zone offers significant long-term benefits for Turkey as well. It provides ample territory for the resettlement of Syrian refugees and it prevents the Kurdish People’s Protection Units (YPG) — an affiliate of the Kurdistan Workers’ Party (PKK), a Turkish based designated foreign terrorist organization — from consolidating its territories along the Turkish border. All of this was accomplished with minimal casualties.

Ankara may be pleased with how this operation has gone so far, but problems are just around the corner. If ISIL chooses to offer serious resistance, Turkey will not have such an easy path to victory as it attempts to take al-Bab, an urban city south of their buffer zone. So far, ISIL has put up little effort in stopping advancing Turkish backed rebel forces, preferring to withdraw after placing mines and improvised explosive devices (IEDs). Satellite imagery and information from key rebel sources on the ground suggest that ISIL has prepared al-Bab for siege.

The rebels of Euphrates Shield are ill prepared for the grueling urban combat that taking al-Bab will entail. Even for a competent infantry force, this would be a difficult operation, perhaps akin to the First and Second Battles of Fallujah. A poorly trained rebel infantry force, even if backed by Turkish forces, will have an even harder time. Tensions between Islamist groups and U.S.-backed rebel groups, as well as a lack of rebel manpower, will further compound the challenges.

Al-Bab: ISIL’s Fortified Stronghold in Northern Aleppo

Thus far, Turkish and Syrian rebel forces have largely fought their battles in the countryside and small, unpopulated villages, where ISIL is at a massive disadvantage. Empty farms provide ISIL little cover from Turkish and American aircraft. Turkish T-155 Fırtına artillery has been used to devastating effect against ISIL fighters in open fields. Turkish M60T Sabra and M60A3TTS tanks can engage targets from thousands of yards away with relative ease in flat, rural areas. Once in a dense urban area like al-Bab, however, the situation will be different.

The capture of Dabiq made international headlines, but the town itself is actually quite small with a pre-war population of 3,364. Al-Bab had a pre-war population just over 63,000. The battle for al-Bab would be comparable to the battle for the city of Manbij further to the east. It took the far better trained and organized YPG nearly three grueling months to capture Manbij from ISIL. Northern Aleppo rebels have neither the experience nor the organization to easily pull off such an operation.

The sheer size of al-Bab is not the only issue that Euphrates Shield faces. Analysis of satellite imagery shows that ISIL constructed a large defense network in and around the city this summer. A 20 kilometer defensive wall now envelops the entire city, its countryside, and the town of Tadef to the south. Additional areas around the city including the al-Bab grain silos, Sheikh Aqil hill, the town of Tadef, and the al-Bab Hospital are likely to serve as key defense points.

The amount of effort ISIL has put in building these defenses suggests they are going to stand and fight for al-Bab rather than withdraw. Free Syrian Army (FSA) sources in northern Aleppo have confirmed that rebel victories near and around Dabiq were partially the result of ISIL withdrawing to reinforce al-Bab. Al-Bab is by no means an impenetrable fortress, but Euphrates Shield cannot easily take the city as they did with Jarablus.

The Rebels of Euphrates Shield: Divided, Poorly Trained and Low on Men

Even a well trained force would have trouble taking al-Bab and the rebels are not well trained, even by Syrian standards. Good marksmanship is the exception rather than the rule. Key groups in Euphrates Shield, such as the American armed and trained al-Moutasem Brigade, routinely fail to sink mortar base plates resulting in inaccurate and ineffective mortar fire. Many of the rebels have little combat experience, having been recruited from refugee populations in Turkey just prior to the start of the operation.

A lack of manpower is another a major issue for northern Aleppo rebels as shown by the aforementioned recruiting drive. Syrian government victories against rebels in Aleppo city has made it harder for Turkey to recruit from core rebel areas elsewhere in northern Syria. For rebels in that part of Syria, breaking the Syrian government siege of rebel-held eastern Aleppo is more of a priority fighting alongside Turkey in northern Aleppo. For instance, the U.S.-backed Free Syrian Army Mountain Hawks Brigade withdrew from Euphrates Shield in mid-September due to government advances around Aleppo City.

Internal divisions within northern Aleppo rebels also bodes badly for a Turkish-led offensive against al-Bab. Relations between Islamist rebels, like Ahrar al-Sham, and American backed FSA groups, such as the al-Moutasem Brigade, have been poor for some time. Al-Moutasem is strongly disliked by many Islamist rebels due to their close association with the United States. For instance, Islamist rebels briefly kidnapped an al-Moutasem commander in June 2016. In recent weeks, tensions between Ahrar al-Sham and American backed FSA Hamza Division have risen over Ahrar units refusing to allow the burial of a deceased Hamza Division commander in his hometown. Such tensions are not visible to outsiders but can seriously damage the coordination and trust between rebels that is needed for a successful offensive on al-Bab.

The Battle For Al-Bab: No Walk in the Park

Barring a rapid collapse of the self-proclaimed caliphate, ISIL can and will likely stand its ground. The dense, urban nature of al-Bab nullifies or reduces the effects of Turkish aircraft, artillery and armor. Both satellite imagery and local sources on the ground suggest that ISIL is likely to hold fast in the city, rather than withdraw as they did in Jarablus at the onset of Turkey’s intervention in Syria.

A lack of properly trained rebels also casts doubts on an easy path to victory at al-Bab. Urban sieges in Syria generally require a numerically superior attacking force. With many rebels leaving northern Aleppo and returning to other parts of Syria, Euphrates Shield does not have the required manpower to easily take the city from ISIL. Fractures in the rebel coalition may decrease cooperation between rebel groups, which in turn hinders battlefield effectiveness.

While the Turkish government and various Free Syrian Army factions have stated that they will next proceed to al-Bab, this is by no means guaranteed. An unexpected occurrence, such as a Syrian government offensive on al-Bab from the south or a rapid YPG offensive towards to the city from the east and west, could easily end rebel hopes of taking the city. That being said, if Turkey follows through with their statements and tries to take al-Bab, we should not expect an easy, rapid Euphrates Shield victory.

Rao Komar (@RaoKomar747) is a Junior Intelligence Analyst at the SecDev Group and an Arabic Scholar at the University of Texas at Austin’s Arabic Flagship Program. He is currently pursuing a bachelor’s degree in International Relations and Global Studies at UT Austin.