Inter-rebel conflict during the Syrian Civil War

The inter-rebel conflict during the Syrian Civil War started after fighting erupted between the Syrian opposition groups: the Free Syrian Army (FSA), the Army of Mujahedeen, the Islamic Front, and the Islamic State of Iraq and the Levant (ISIL). In early January 2014, serious clashes between the groups erupted in the north of the country. Opposition groups near Aleppo attacked ISIL in two areas, Atarib and Anadan, which are both strongholds of the fundamentalist Sunni organization. Despite the conflict between ISIL and other rebels, one faction of ISIL has cooperated with the al-Nusra Front and the Green Battalion (a group of Saudi fighters) to combat Hezbollah in the Qalamoun region.

Background

The Free Syrian Army clashed with Jabhat al Nusra on various occasions in 2013. Tension between moderate rebels and ISIL had been high since ISIL attacked and captured the FSA-held border town of Azaz in Northern Aleppo and the nearby Bab al-Salameh border crossing with Turkey, which serves as an important supply route for rebel forces; this took place between 18–23 September 2013. The conflict was renewed over Azaz in early October and in late November ISIL captured the border town of Atme from an FSA brigade. On 31 December 2013, the body of doctor Hussein Suleiman was handed over in a prisoner swap between ISIL and rival rebel forces. Suleiman was tortured and died in ISIL custody. The opposition National Coalition and activists accused ISIL of serving the interests of the Syrian government by tarnishing the image of their uprising.

Rebel-ISIL conflict

Start of the rebel offensive, ISIL counter-offensive, and mutual advances

On the evening of 2 January 2014, ISIL forces attacked the rebel-held town of Atarib, where they were accused of two recent incidents of killing or kidnapping mainstream rebel commanders. On 3 January, several civilian protests, counting hundreds of people, were organized against ISIL and to commemorate the death of Suleiman across the Aleppo Governorate. In the Idlib village of Kafr Takharim, ISIL opened fire on the protesters. There were no reports of casualties. In response to the attack on the protesters, two newly formed Islamist rebel groups of the FSA attacked ISIL positions in more than half a dozen locations in the governorates of Aleppo and Idlib.

Rebels in Atarib managed to repel the ISIL attack on the town, after which the ISIL fighters were surrounded, resulting in the capture of a Tunisian commander, Abu Saber al-Tunisi. It was unclear if he was summarily executed by the rebels. 42 ISIL fighters were wounded in the fighting in Atarib, while an opposition media activist was killed while covering the clashes. There were unconfirmed reports of rebels arresting ISIL members in various towns and villages in the Aleppo Governorate and the Idlib Governorate. Fighting raged in the Idlib village of Maarrat Misrin, while in the village of Kafr Nabl, rebel forces surrounded an ISIL facility, giving its fighters 24 hours to surrender. Meanwhile, the rebel Islamic Front, which was also engaged in the fighting against ISIL, sent reinforcements to the ISIL-held town of Azaz.

On 4 January, ISIL were reported to be rounding up "suspect activists" in both Saraqeb and Kafr Nabl. In the Harem area, ISIL forces executed 30 captives, including civilians, after their base was surrounded by rebel forces. In Aleppo, fighting raged throughout the province, with rebel forces making advances against ISIL. FSA units were reportedly making progress in Atarib, but ISIL was surrounding the town and shelling it.

ISIL was also on the offensive, attacking rebel positions and ambushing their forces in attacks that left 24 rebels dead. One attack included a car bomb. At this point, ISIL gave a 24-hour ultimatum to rebel forces attacking them, saying that they would withdraw from Aleppo, allowing government forces to enter rebel territory, if they did not stop their attacks. The rebels reiterated an earlier call on ISIL fighters to defect to their side.

On 5 January, rebels captured an ISIL base in Manbij after heavy fighting. Clashes had also erupted in the town of Tabqa, in the Ar-Raqqah Governorate, and fighting spread to the central Hama Governorate, where ISIL killed seven rebel fighters. During the fighting in Manbij, ISIL used car bombs to defend its territory. Meanwhile, ISIL forces retreated from al-Dana and Atme in the Idlib Governorate, and started heading in the direction of Aleppo. Their positions were overrun by the al-Nusra Front and Ahrar ash-Sham groups, in a possible deal to avoid larger confrontations. ISIL also retreated from Darat Izza, while they managed to retain control of Saraqeb and Kafr Zita. ISIL reinforcements were dispatched from Ar-Raqqah to Aleppo. Overall, 66 combatants, including 11 ISIL fighters, were killed during the day.

According to the opposition Sham News Network, by this point, rebels had captured more than 80% of the ISIL-held Idlib countryside and 65% of ISIL territory in Aleppo and its countryside.

By 6 January, rebels had besieged ISIL in its stronghold of Ar-Raqqah. During the fighting, rebels released 50 prisoners from ISIL custody. Among those rescued was a Turkish news photographer who had been kidnapped since December 2013. 10 Syrian Kurdish prisoners also managed to escape. 70 ISIL and 20 rebel fighters had been killed since the rebel attack on Ar-Raqqah started, according to a rebel officer who expected that it would take them at least a week to drive the al-Qaida linked militants out of the city. Meanwhile, ISIL detonated a car bomb by a rebel checkpoint near the town of Darkush, 20 rebel fighters were killed in the suicide attack on the checkpoint. ISIL fighters retreated from Kafr Zita, In Jarablus, a mile and a half from the Turkish-Syrian border, there were conflicting reports with the Islamic Front stating they had overrun the local ISIL headquarters, with the ISIL denying that and insisting that the group was holding fast.

On 7 January, it was confirmed that 34 foreign ISIL and Jund al-Aqsa fighters had been executed in the previous few days by rebels in the Jabal al-Zawiya area. ISIL retreated from al-Mayadeen in Deir ez-Zor Governorate, without any fighting with rebel forces. East of Rastan, in the Homs Governorate, ISIL attacked a rebel headquarters, killing 15 rebel fighters. During the day, it was revealed that during the previous evening, ISIL executed up to 50 prisoners in the Qadi al-Askar district of Aleppo. The dead included media activists, relief workers, and other civilians. According to the opposition SOHR, 42 people were executed, including, 21 rebel fighters and five media activists.

On 8 January, rebels captured the ISIL headquarters in Aleppo city at the Children's hospital in the Qadi Askar district. ISIL forces lost control over opposition-held areas of the city and retreated to Al-Inzarat on the northeastern outskirts of Aleppo. 300 hostages held by the radical jihadists were set free. In Ar-Raqqah, the hospital was abandoned, bodies were lying in the central square and there was no power or water leaving the city "completely paralyzed", according to an opposition activist. At this point, ISIL controlled two key routes out of Raqqa: to the east toward the Iraqi border and also the road north to the Turkish frontier. The head of the al-Nusra Front, Abu Mohammad al-Golani, confirmed that fighting had taken place between his organization and ISIL and called for mediation and an end to the "infighting." Late in the day, ISIL started a counterattack, as it launched car bomb assaults targeting opposition checkpoints. Three attacks took place in Al-Bab, Hreitan, and Jarabulus in the Aleppo Governorate, Observatory director Rami Abdel Rahman told AFP. He said similar overnight attacks took place in the Aleppo Governorate, while one occurred in Mayadin in the eastern Deir ez-Zor Governorate. The attack in Al-Bab killed nine people.

On 9 January, ISIL sent reinforcements from Deir ez-Zor to back its fighters in the Aleppo countryside. According to local residents, ISIL was preparing many suicide attacks in retaliation for the rebel attacks, and that their commanders were wearing explosive belts all the time. Dutch journalist Lex Runderkamp told Dutch news program NOS that the ISIL reinforcement convoy was 1,300 men strong, including ISIL special forces from Iraq. In Ar-Raqqah, the rebels took control of the political intelligence building, which was located 400 meters from the main ISIL headquarters. However, ISIL still controlled the bridges leading into the city, which left people using boats to get into Ar-Raqqah, and later in the evening, ISIL forces seized the Mashlab district and an al-Nusra Front base in the city. Clashes erupted between ISIL and a rebel brigade by the Castillo road, in Aleppo Governorate. The rebels blocked an ISIL supply route between al-Jandoul and Castillo. Meanwhile, Islamist rebel brigades sent reinforcements to the Bab al-Salama border crossing, at Azaz, which is primarily controlled by ISIL. In Idlib province, ISIL opened fire on a demonstration in Kafartkharim and besieged several field clinics, and stormed one of them, searching for rebels injured earlier in the morning during clashes in Atarib.

According to SOHR, local ISIL forces signed a truce with the Islamic Front and several independent Islamist rebel units in Al-Hasakah Governorate. They agreed with the establishment of a single military command center and legal authority for the area.

On 10 January, ISIL managed to push back rebel forces on the eastern approaches to Ar-Raqqah. ISIL forces also killed 20 rebel fighters in fighting in the town of Al-Bab in Aleppo province, and managed to capture wheat silos and mills just outside the town. ISIL commander Abu Omar al-Shishani entered the town with a convoy of 30 vehicles and troops after he lifted the ISIL's siege of Deir-az-Zor airport.

On 11 January, rebels moved a convoy including tanks and technicals to Saraqeb in preparation to push ISIL out. Heavy fighting erupted and it was reported that rebels took over most of the town, and besieged hundreds of ISIL fighters. Earlier in the day, five rebels were killed on the outskirts of Saraqeb when their car hit a bomb. Meanwhile, ISIL forces managed to capture the border town of Tal Abyad, while in Ar-Raqqah ISIL fighters captured a rebel checkpoint and the train station. ISIL fighters also dumped the corpses of dozens of their foes at the village of Jazra, to the west of Ar-Raqqah. Dozens of bodies of ISIL fighters were also reportedly in Ar-Raqqah's hospital. Rebels managed to regain territory lost in previous days in Aleppo province and were defending against ISIL counterattacks. 20 rebels were killed in fighting in the town of Anadan, while 30 rebels were killed in three days of fighting in the village of al-Tiba, northeast of Sekhna.

On 12 January, it was confirmed that rebel forces had captured the eastern part of Saraqeb with the local ISIL commander surrounded with his fighters in the center of the town. Fighting was still continuing in Ar-Raqqah between ISIL and remnants of rebel units, including the Al-Nusra Front, although by this point ISIL had captured much of the city. According to an opposition activist, 95 percent of Ar-Raqqah and its countryside were under ISIL control. ISIL forces had also captured the towns of Hrietan and Basraton in Aleppo province. It was also reported that the bodies of 70 rebels were delivered to Ar-Raqqah's hospital after they were executed by ISIL following their capture of Tal Abyad. Another report put the number of executed prisoners at 100.

On 13 January, it was reported that ISIL had won the battle for of Ar-Raqqah capturing most of the province and the provincial capital. ISIL had also captured Al-Bab and Beza'a, while the rebels were gaining ground in Jarabulus, near the Turkish border. Another mass execution of prisoners was also reported near the village of Kantari, about 80 kilometers north of Ar-Raqqah, when ISIL killed 46 captured fighters of the Ahrar ash-Sham rebel group. 14 rebels were also executed in Homs province

On 14 January, it was reported that rebels captured the villages of Masqan, Kafar Kalbin and Kafra in Aleppo province, while the ISIL has taken full control of Ar-Raqqah city, after the last remaining rebels retreated. Meanwhile, the rebels also captured the prison in Jarablus, releasing 70 prisoners from ISIL custody.

On 15 January, an ISIL car bomb in Jarablus killed 26 people, of which 23 were rebel fighters and three were civilians. Meanwhile, in Saraqeb fighting was continuing and opposition sources reported that the local ISIL commander, a Belgian, was killed. ISIL denied the claim. Between 15 and 17 January, rebels captured Jibreen, Hardntin Kfarrakeshr, Sheikh Ali, Aajel, 46th base, Orum al-Sughra and Reef al-Muhandiseen, while the ISIL retreated from the village of Kafarjoum, which holds the largest ISIL arms depots in all of Syria. ISIL also withdrew from Saraqab, burning their vehicles as they retreated, while at the same time ISIL recaptured Jarabulus.

On 20 January, 2 suicide cars exploded at the Bab Al-Hawa border crossing, 16 people including six rebels were killed. The same day, ISIL forces seized control of the Al-Jarah military airport. In Manbij, a large suicide car explosion killed 20 people, including rebels, women, and children By 23 January, ISIL was in full control of Manbij and completely secured Darkush the following day.

On 27 January, it was reported that ISIL senior Commander Sameer Abid Mohammed al-Halefawi (aka Haji Bakr) was killed by rebels in Tal Rifaat, near Azaz, and at least two other ISIL senior commanders were captured at Hreitan. Four ISIL fighters and three rebels were killed in the fighting. ISIL confirmed the death of top ISIL leader Haji Bakr on 2 February.

Al Qaeda breaks links with ISIL and al-Nusra Front joins the fight

On 1 February, ISIL attacked the headquarters of the Liwa al-Tawhid Brigade in Aleppo, killing the brigade commander Adnan Bakour and 15 other rebels at the cost of at least 9 ISIL fighters. The next day, Al-Qaeda distanced itself from ISIL and its actions in Syria.

On 3 February, the Ar-Raqqah Rebels Brigade launched a military operation against ISIL checkpoints and strongholds in Ar-Raqqah. The day before, five ISIL fighters were assassinated in the Ar-Raqqa national hospital.

On 5 February, a local group of Suqour al-Sham brigade in Hama and ISIL signed a truce, It was also reported that The Front of Aleppo Islamic Scholars issued a statement, giving the ISIL fighters in Syria a three-day ultimatum to either return to Iraq or join other armed factions fighting against the Syrian government.

On 8 February, the Al-Nusra Front and allied rebel factions launched an offensive against the ISIL in the Deir ez-Zor Governorate. It was reported that the ISIL emir of Deir al-Zor, Abu Dajana, was killed in the clashes and the rebels also recaptured facilities in the province. At the same time, 13 foreign ISIL fighters defected in Ar-Raqqa. Between 10 and 12 February, ISIL had almost completely withdrawn from the eastern province of Deir ez-Zor, including the city of Deir ez-Zor.

On 23 February, two ISIL suicide bombers killed a number of rebels in Aleppo, including Abu Khaled al-Suri, who was Al-Qaeda's representative in Syria and top-commander in the rebel group Ahrar ash-Sham. Three days later, the Tunisian ISIL deputy Emir for the Ar-Raqqa province and three other fighters were killed by a roadside bomb, while rebels captured the village of Kafrnaya in Aleppo. It was also reported that ISIL released a rebel commander in Ar-Raqqa.

On 28 February, it was reported that ISIL has begun retreating from the following places in Aleppo province towards Ar-Raqqa: Azaz, Menagh military airport, the Mayer region and the villages of Deir Jamal and Kafin. ISIL has regrouped in particular at their strongholds Jarabulus and Manbij. Azaz was captured by rebels after the ISIL withdrawal.

Ongoing clashes, ISIL retreats from Idlib and Latakia

Main article: Battle of Markada

On 3 March, SOHR reported that ISIL was responsible for the kidnapping of the commander of the rebel "United Front for Southern Damascus" in February 2014.

On 11 March, ISIL massacred at least 22 people, including 12 rebels, after they captured the village of Shuyukh near Jarabulus. During this time, ISIL had also captured the town of Karakozak, in Aleppo province near the Turkish border. The next day, the ISIL emir Abu Mouhammad Al-Massri was assassinated by the FSA affiliated Al-Raqqa Revolutionaries Brigade in the Ar-Raqqa's Tal-Dikan area, near the village of Sarreen.

On 14 March, it was reported that ISIL fully retreated from Idlib and Latakia provinces.

On 16 March, according to local sources a number of foreign ISIL fighters defected to Al-Nusra after they killed their commander. The next day, Al-Nusra and the Islamic Front were able to capture the al-Thalja barrier, resulting in the ISIL withdrawal towards Margada town.

On 27 March, ISIL launched an operation against Al-Nusra and allied forces at the al-Jafra oil field and the Koniko gas factory in Reef Deir Izzor. SOHR confirmed that the ISIL took hold of these facilities, but were forced to withdraw after heavy clashes two days later. On 29 March, ISIL captured the town of Markadah, after the rebels retreated to Al-Sor town in the eastern countryside of Der-Ezzor. At least 35 rebels were reportedly killed by the ISIL in the fighting and many rebels were captured. The SOHR confirmed the death of at least seven ISIL fighters.

ISIL's Deir ez-Zor offensive

Main article: 2014 Deir ez-Zor offensive

On 10 April, ISIL launched an offensive against the rebels in Deir ez-Zor Governorate launched a three-pronged assault on rebel positions in and near the border town of Albu Kamal and reportedly took control of parts of the town.

Between 10 and 13 May, ISIL gained control of important parts of Eastern Deir ez-Zor province and districts of Deir ez-Zor city from rival rebel forces. and gained control of at least five villages in the northern countryside of Al-Raqqa province. ISIL also executed the military commander of the Al-Raqqa rebel brigade and his nephew near Ayn Issa in Al-Raqqa province.

By late May, 3,000 ISIL fighters were involved in the offensive in Deir ez-Zor and gained control of the Al-Kharrat oil terminal in Deir ez-Zor province.

On 2 June, ISIL took full control of Al-Besera, while at the same time the rebels counterattacked, reclaiming 16 villages.

On 5 June, ISIL gained control of the entire western countryside of Deir ez-Zor after Al-Nusra forces withdrew following an assault by Chechen and Afghan ISIL fighters. On 8 June, the FSA reportedly assassinated the ISIL emir of Homs. By 10 June, the offensive into Deir ez-Zor had expanded and ISIL had reportedly driven Al-Nusra and aligned militants from nearly all of the province north of the Euphrates.

Since the start of the ISIL offensive in Deir ez-Zor, the pace of defections from the opposition to ISIL had accelerated, most significantly in the town of Al-Muhasan and adjacent villages, where a mass defection by the rebel garrison granted ISIL uncontested control over a key route to the provincial capital.

Between 21 and 22 June, ISIL captured eight towns in the northern part of Aleppo governorate, with the help of American-made Humvees seized in Iraq. Two of the towns were located near the town of Azaz on the border with Turkey.

Between 1 and 3 July, ISIL, bolstered by reinforcements from Iraq, captured Abu Kamal, Mayadin and Shuhail. ISIL also gained control of Syria's largest oil field, al-Omar in Deir ez-Zor province, after Al-Nusra forces fled the facility. By this point, the entirety of the province with the exception of the provincial capital, its airport, and a few villages had fallen to ISIL. Following this, ISIL captured the villages of Quniya and Buqris, close to the town of Mayadin.

On 14 July, ISIL expelled Nusra and other assorted rebel groups from all rebel-controlled neighborhoods in Deir ez-Zor city. By this stage, ISIL controlled between 95% and 98% of Deir Ez-Zor province.

East Ghouta fighting

On 1 July 2014, clashes erupted between Jaysh al-Islam and ISIL in the Eastern Ghouta town of Medaa. ISIL captured 25 of their fighters and executed an unknown number of them. The next day, Jaysh al-Islam reportedly expelled ISIL fighters from the Ghouta town of Maydaa in Damascus province.

One week later, a key commander of Jaysh al-Islam, Abu Mohammad Haroun, was assassinated by ISIL by a roadside bomb in the Ghouta suburbs.

Following ISIL's victory in Deir ez-Zor, it was reported that the entirety of Dawoud Brigade, a thousand strong division of the Jaysh al-Sham defected to ISIL. The defection of Dawud is reported to have bolstered ISIL forces in Raqqa with more than a hundred combat vehicles, at least ten of them tanks.

Aleppo fighting

On 13 August 2014, it was reported that IS seized control of eight villages and several towns in Aleppo province from rebels, including Turkmen Barah and Akhtarin; the fighting reportedly killed 40 rebel fighters and 12 IS members. By 16 August, IS captured around 10 villages and towns and was advancing towards Marea and Azaz. Fighting raged near Marea, the main base of Islamic Front rebel group, where rebel reinforcements were being sent. During the day, IS forces captured three villages near Marea. Additionally, by 18 August opposition sources had reported the mass defection of the Aleppo-based Khaled Rashed, Green and Tawhid-e-jihad brigades to the Islamic State. On 24 August, rebels recaptured two villages, and on 27 August, started an offensive called Nahrwan Al-Sham to expel IS from the northern and eastern Aleppo countryside; opposition sources claimed that rebels had regained control of several villages and killed 43 IS fighters.

In early April 2015, ISIL bolstered its forces in the northern Aleppo countryside after having withdrawn significant quantities of war material just two months before. A double car bomb attack killed 31 rebels near Aleppo.

On 31 May, ISIL seized the town of Sawran and numerous other villages from the rebels, leaving them just 30 miles away from the Bab al Salam border crossing. The militants beheaded captured rebel fighters in the seized villages and kidnapped their families. Fighting raged all along the 35 mile frontline as the militants pressed towards Azaz; rebels reportedly requested coalition air support and received none.

As Turkey announced plans for a rebel controlled ‘buffer zone’ in northern Aleppo to counter the Islamic State, Syrian rebels expressed skepticism that the Turkish plans would impact the battle, claiming the coalition had not consulted them. Fighters from the US trained "Division 30" were reported to have entered Syria and taken positions in Azaz with the intention of coordinating with rebel groups to push back ISIL. The United States and Turkey continued to disagree over which rebel groups should be provided with support.

On 30 July, seven Nusra fighters were killed when a car bomb exploded at a checkpoint near the town of Malikiya. Clashes subsequently broke out between Nusra and ISIL. On 9 August, ISIL captured the village of Umma Housh, a village that lies along a rebel supply line into Aleppo, after a night time assault involving two suicide bombers, killing at least 37 rebels and 10 ISIL fighters. On 10 August, Nusra announced it was withdrawing from the frontline with ISIL in protest over Turkish and US plans for a safezone in Aleppo province.

On 27 August, ISIL launched a major offensive on the opposition bastion of Marea. ISIL fighters captured two villages that Nusra had withdrawn from while taking three villages neighboring Marea, enveloping it in a pincer movement on three sides and killing dozens. On 5 September, ISIL pushed into Marea from the north, rebels entrenched in the town attempted to resist as ferocious fighting killed 47 on both sides. On 8 September, it was reported that the rebels had managed to push ISIL back to the outskirts of the town, but were still surrounded on three sides. ISIL was pounding Marea with high-powered weaponry, suicide bombs, artillery, and chemical weapons. US airstrikes were intensifying around the town in an attempt to halt the jihadist advance.

On 9 October, ISIL captured five villages as well as the Infantry School on the outskirts of Aleppo in a lightning attack that brought them to within 10 miles of the city Later that day, Ahrar al Sham managed to recapture one of the villages and was battling to regain a second.

Kobanî

Main article: Siege of Kobanî

In the summer of 2014, ISIL began taking over the area south of the Turkish border and then started to besiege the town of Kobanî. The Kurdish People's Protection Units were assisted by the FSA groups Dawn of Freedom Brigades, Liwa Thuwwar al-Raqqa, the Al-Qassas Army and the Jarabulus Brigade during the defense of Kobanî against ISIL.

On 26 January 2015, YPG and rebels recaptured the town of Kobani.

Battle for Eastern Qalamoun and Yarmouk

Main article: Battle of Yarmouk Camp (2015)

In 2015, most of the fighting between the rebels and ISIL took place in the Rif Dimashq Governorate, while some factions from both parties chose to fight together against the Syrian Army, Lebanese Army and Hezbollah in the border area with Lebanon.

On 26 February 2015, ISIL fighters attacked rebels in the area of Dakwa, in the countryside east of Damascus, and took control of it.

On 13 March 2015, a rebel joint-force consisting of Jaysh Usud al-Sharqiya, Ahmad al-Abdo Martyrs Brigades and Battalions, al-Nusra Front, Jaysh al-Islam and Ahrar ash-Sham launched an offensive against ISIL in the eastern Qalamoun area. They reportedly captured the Bir al-Mahrotha area and killed the ISIL leader Abu Haidara Al-Tounisi that day. Two days later, the rebels captured "wide parts" of the al-Zarka area and the al-Qaryatayn mountains from ISIL.

On 19 March 2015, rebels attacked ISIL positions in al-Kafat area, after an al-Nusra Front suicide attack, and reportedly advanced.

On 1 April 2015, ISIL, reportedly facilitated by Nusra's local wing, stormed Yarmouk refugee camp in the area outlying central Damascus. Quickly taking control of wide swaths of the camp, the militants engaged in drawn out battles with anti-Assad rebel fighters and the Hamas affiliated Aknaf Bait al-Maqdis before a rebel offensive managed to regain some of the camp the next day. However, ISIL militants re-entered the camp the following day and seized up to 90% of it.

On 5 April 2015, rebels announced an offensive against ISIL in the Syrian desert and reportedly captured the Alyaniah mountains. The SOHR reported that seven fighters from both sides were killed in the al-Mahesa area. Three rebels were captured by ISIL as well.

On 12 April, Jaysh al-Islam and allied forces launched a counter-attack on the ISIL-held Hajar al-Aswad district. On 17 April, Jaysh al-Islam and the 1st Brigade also launched an offensive against ISIL in the neighborhoods of al-Qaboun, Jobar and Barzah.

On 22 April, ISIL captured wide parts of al-Mahsa area, in the eastern Qalamoun, and cut off the rebel supply line between Jordanian border and the Syrian al-Badia. According to one report, 30 rebels and at least 12 ISIL militants were killed, while another stated nearly 100 rebels were dead or missing. A pro-opposition source stated ISIL recaptured all areas they lost to the rebels in the previous four months.

Southern Syria fighting

Between 27 and 29 April 2015, fighting raged south of Quneitra city, near the Israeli-held Golan Heights, between an ISIL-linked rebel group Jaysh al-Jihad on one side and al-Nusra and FSA fighters on the other. The clashes started after a pair of Jaysh al-Jihad ambushes on rebel convoys preparing an offensive against government forces. The rebels besieged 200 Jaysh al-Jihad fighters in the village of al-Qahtania and took control of wide areas the group controlled. On 29 April, fighting also erupted in Daraa province between al-Nusra and the Yarmouk Martyrs Brigade, which was accused the previous month of also pledging allegiance to ISIL. The Yarmouk Martyrs Brigade captured an al-Nusra post in the town of Sahem al-Jolan. On 30 April, rebel forces captured the Quneitra border crossing from the Jaysh al-Jihad and on 5 May, al-Qahtania. Overall, the fighting left 59 rebels, 32 Jaysh al-Jihad fighters and two members of Yarmouk Martyrs Brigade dead.

Attempted mediation

On 19 January 2014, ISIL reached out to other rebel groups in Syria to stop the rebel in-fighting, by posting an audio message online. On 4 April, Al-Qaeda chief Ayman al-Zawahri called on the rival jihadists and rebels to end the infighting, stating that the violence is "sedition". In early May, Ayman al-Zawahiri again called on ISIL and the Al Nusra Front to stop their fighting. However, fighting continued between the two groups. The Al-Nusra Front issued a statement on 4 May 2014 in which it agreed to stop fighting with ISIL, however, it stated that it will retaliate if ISIL attacks first. In May 2014, ISIL launched an offensive against Al-Nusra and allied groups in Deir ez-Zor Governorate, seizing oil wells and leaving hundreds dead on both sides.

In September 2014, moderate rebels and the Islamic State signed a non-aggression pact in Al-Hajar al-Aswad. However, the report of a truce has been denied by the Islamic Front, the Syria Revolutionaries Front, and other rebel groups.

Islamic Front-Free Syrian Army conflict

In December 2013, the Islamic Front, mainly composing of Ahrar ash-Sham, took over several bases at the Bab al-Hawa Border Crossing from the Supreme Military Council and removed the FSA's revolutionary flags. The Islamist fighters captured some SMC guards and seized thousands of small arms and ammunition. As a result, the Islamic Front withdrew from the SMC.

In early March 2016 Jaysh al-Islam clashed with Faylaq al-Rahman in Zamalka, Markaz Rif Dimashq District. The groups fought for control of a building in the suburbs, resulting in the latter group expelling the former from the building and the streets. The two groups also clashed over the recruitment of fighters from the Ajnad al-Sham Islamic Union. On 28 April, Legion, supported by the al-Nursa Front and Ahrar ash-Sham, attacked JaI in eastern Ghouta, however, Ahrar ash-Sham denied involvement. Faylaq al-Rahman's Air Defense Brigade subsequently defected to Jaysh al-Islam. By 17 May, more than 500 fighters on both sides and a dozen civilians had been killed in the fighting in East Ghouta.

On 26 March Ahrar ash-Sham ordered the anti-YPG Kurdish FSA group Liwa Ahfad Saladin to remove the flag of Kurdistan from their posts and threatened military action if they didn't.

Al-Nusra Front-FSA conflict

Al-Nusra Front–SRF/Hazzm Movement conflict

Main article: al-Nusra Front–SRF/Hazzm Movement conflict

In October 2014, al-Nusra Front, along with Jund al-Aqsa, clashed with the Syria Revolutionaries Front in Idlib. At the same time al-Nusra also attacked the Hazm Movement in Aleppo.

In January 2015, clashes between the Hazm Movement and al-Nusra spread from Aleppo to Idlib.

Southern Front

Although the Southern Front of the Free Syrian Army have long cooperated with al-Qaeda in the ground against the Syrian government, ideological tensions between some of their factions brewed in 2014. Ahmad al-Nemeh formed the Daraa Military Council and was subsequently captured and tortured by Nusra as the latter threatened to arrest any member of this new coalition.

During the Quneitra offensive (June 2015), the Southern Front rejected any cooperation with al-Nusra, the Army of Conquest therefore participated in the operation separately.

In the Quneitra offensive (October 2015) both Jaish al-Fatah and the Southern Front claimed they captured the UN Hill in the area, later that month, the Southern Front and Nusra clashed in Daraa.

Clashes between the 13th Division and al-Nusra

Main article: Second Battle of Maarat al-Nu'man

In March 2016 there were several pro-FSA protests and demonstrations against the Syrian government throughout rebel-controlled territory in Syria. Al-Nusra Front attempted to crack down on the protests in Idlib, in response, the FSA's 13th Division raided al-Nusra's headquarter in Maarrat al-Nu'man.

Al-Nusra retaliated by shelling Division 13's headquarter in the city. SOHR claimed that Jund al-Aqsa joined the conflict and established checkpoints in support of JaN. According to the 13th Division's media wing, their position was overran and 4 of their fighters were killed.

Ahrar ash-Sham-al-Qaeda clashes

On 17 March 2016 Jund al-Aqsa members attempted to hold a mourning service at a tent for the death of an ISIL commander in Sarmin, Idlib Governorate. Ahrar ash-Sham fighters then entered the tent and forced them to end the ceremony, sparking a gunfight between the two groups. In response, Jund al-Aqsa fighters set up checkpoints in the town, intending to arrest Ahrar ash-Sham members.

On the same day or the next day, Abu Sakkar, an al-Nusra Front commander infamous for eating a dead Syrian soldier's heart when he was the commander of the Farouq Brigades in 2013, was stopped at an Ahrar ash-Sham checkpoint while driving on the road between the towns of Salqin and Harem. The Ahrar fighters attempted to arrest him when he resisted arrest and drove away toward Harem, resulting in a pursuit by the Ahrar militants. Upon reaching the town, Abu Sakkar attempted to reach for his gun and was fatally shot by his pursuers.

Inter-FSA conflict

Main article: Syrian Kurdish-Islamist conflict (2013-present)

In late November 2015, there were clashes between the Army of Revolutionaries, supported by the YPG, and the FSA-dominated Mare' Operations Room in the northern Aleppo Governorate, backed by Ahrar ash-Sham and the al-Nusra Front. However, both the YPG and al-Nusra denied involvement in the conflict.

In December the conflict between the Syrian Democratic Forces, mainly composing of the YPG and the Army of Revolutionaries and the Mare' Operations Room escalated in northern Aleppo. The latter called on Jaysh al-Thuwar to leave the SDF and sever relations with the PYD, while the former accused the latter of being led by Ahrar ash-Sham and Nusra.

Casualties

Between 3 January and 28 June 2014, 5,641–6,991 people had been killed in the inter-rebel fighting, according to the SOHR. By 25 February 2014, ISIL had conducted 34 suicide attacks. On 26 August 2014, the Syrian Network for Human rights reported that since the declaration of the Islamic State on 9 April, 2,691 anti-ISIL rebels and 782 civilians had been killed.

Between 28 June 2014 and 29 February 2016, Islamic State militants executed a total of 4,225 people: 2,262 civilians, 1,159 government soldiers, 464 Islamic State deserters, 322 rebel and Kurdish fighters, 7 alleged government spies (including a child), 5 Iraqi citizens, 3 military deserters and one former ISIL member.