Inter-rebel conflict during the Syrian Civil War

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

Background
Tension between moderate rebels and ISIS had been high since ISIS attacked and captured the FSA-held border town of Azaz in Northern Aleppo and the nearby Bab al-Hawa 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 ISIS 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 ISIS and rival rebel forces. Suleiman was tortured and died in ISIS custody. The opposition National Coalition and activists accused ISIS of serving the interests of the Syrian government by tarnishing the image of their uprising.

Start of the rebel offensive, ISIS counter-offensive, and mutual advances
On the evening of 2 January 2014, ISIS 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 organised against ISIS and to commemorate the death of Suleiman across Aleppo Governorate. In the Idlib village of Kafr Takharim ISIS 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 ISIS positions in more than half a dozen locations in the governorates of Aleppo and Idlib.

Rebels in Atarib managed to repel the ISIS attack on the town, after which the ISIS 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 ISIS 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 ISIS members in various towns and villages in Aleppo Governorate and Idlib Governorate. Fighting raged in the Idlib village of Maarrat Misrin, while in the village of Kafr Nabl rebel forces surrounded an ISIS facility, giving its fighters 24 hours to surrender. Meanwhile, the rebel Islamic Front, which was also engaged in the fighting against ISIS, sent reinforcements to the ISIS-held town of Azaz.

On 4 January, ISIS were reported to be rounding up "suspect activists" in both Saraqeb and Kafr Nabl. In the Harem area, ISIS 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 ISIS. FSA units were reportedly making progress in Atarib, but ISIS was surrounding the town and shelling it.

ISIS 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, ISIS 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 ISIS fighters to defect to their side.

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

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

By 6 January, rebels had besieged ISIS in its stronghold of Ar-Raqqah. During the fighting, rebels released 50 prisoners from ISIS 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 ISIS 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, ISIS 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. ISIS 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 ISIS headquarters, with the ISIS denying that and insisting that the group was holding fast.

On 7 January, it was confirmed that 34 foreign ISIS and Jund al-Aqsa fighters had been executed in the previous few days by rebels in the Jabal al-Zawiya area. ISIS retreated from al-Mayadeen in Deir ez-Zor Governorate, without any fighting with rebel forces. East of Rastan, in Homs Governorate, ISIS attacked a rebel headquarters killing 15 rebel fighters. During the day, it was revealed that the previous evening ISIS 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 ISIS headquarters in Aleppo city at the Children's hospital in the Qadi Askar district. ISIS 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 laying in the central square and there was no power or water leaving the city "completely paralyzed", according to an opposition activist. At this point, ISIS 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 ISIS and called for mediation and an end to the "infighting". Late in the day, ISIS started a counter-attack as it launched car bomb assaults targeting opposition checkpoints. Three attacks took place in Al-Bab, Hreitan and Jarabulus in Aleppo Governorate, Observatory director Rami Abdel Rahman told AFP. He said similar overnight attacks took place in 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, ISIS sent reinforcements from Deir ez-Zor to back its fighters in the Aleppo countryside. According to local residents, ISIS 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 ISIS reinforcement convoy was 1,300 men strong, including ISIS special forces from Iraq. In Ar-Raqqah, the rebels took control of the political intelligence building, which was located 400 meters from the main ISIS headquarters. However, ISIS still controlled the bridges leading into the city, which left people using boats to get into Ar-Raqqah, and later in the evening ISIS forces seized the Mashlab district and an Al-Nusra Front base in the city. Clashes erupted between ISIS and a rebel brigade by the Castillo road, in Aleppo Governorate. The rebels blocked an ISIS 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 ISIS. In Idlib province, ISIS 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 ISIS 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, ISIS managed to push back rebel forces on the eastern approaches to Ar-Raqqah. ISIS 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. ISIS commander Abu Omar al-Shishani entered the town with a convoy of 30 vehicles and troops after he lifted the ISIS's siege of Deir-az-Zor airport.

On 11 January, rebels moved a convoy including tanks and technicals to Saraqeb in preparation to push ISIS out. Heavy fighting erupted and it was reported that rebels took over most of the town, and besieged hundreds of ISIS fighters. Earlier in the day, five rebels were killed on the outskirts of Saraqeb when their car hit a bomb. Meanwhile, ISIS forces managed to capture the border town of Tal Abyad, while in Ar-Raqqah ISIS fighters captured a rebel checkpoint and the train station. ISIS 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 ISIS 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 ISIS 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 ISIS commander surrounded with his fighters in the center of the town. Fighting was still continuing in Ar-Raqqah between ISIS and remnants of rebel units, including the Al-Nusra Front, although by this point ISIS had captured much of the city. According to an opposition activist, 95 percent of Ar-Raqqah and its countryside were under ISIS control. ISIS 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 ISIS following their capture of Tal Abyad. Another report put the number of executed prisoners at 100.

On 13 January, it was reported that ISIS had won the battle for of Ar-Raqqah capturing most of the province and the provincial capital. ISIS 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 ISIS 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 ISIS 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 ISIS custody.

On 15 January, an ISIS 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 ISIS commander, a Belgian, was killed. ISIS 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 ISIS retreated from the village of Kafarjoum, which holds the largest ISIS arms depots in all of Syria. ISIS also withdrew from Saraqab, burning their vehicles as they retreated, while at the same time ISIS 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, ISIS 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, ISIS was in full control of Manbij and completely secured Darkush the following day.

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

Al Qaeda breaks links with ISIS and al-Nusra Front joins the fight
On 1 February, ISIS 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 ISIS fighters. The next day, Al-Qaeda distanced itself from ISIS and its actions in Syria.

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

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

On 8 February, the Al-Nusra Front and allied rebel factions launched an offensive against the ISIS in the Deir ez-Zor Governorate. It was reported that the ISIS 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 ISIS fighters defected in Ar-Raqqa. Between 10 and 12 February, ISIS had almost completely withdrawn from the eastern province of Deir ez-Zor, including the city of Deir ez-Zor.

On 23 February, two ISIS 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 ISIS 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 ISIS released a rebel commander in Ar-Raqqa.

On 28 February, it was reported that ISIS 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. ISIS has regrouped in particular at their strongholds Jarabulus and Manbij. Azaz was captured by rebels after the ISIS withdrawal.

Ongoing clashes, ISIS retreats from Idlib and Latakia
On 3 March, SOHR reported that ISIS was responsible for the kidnapping of the commander of the rebel “United Front for Southern Damascus” in February 2014.

On 11 March, ISIS massacred at least 22 people, including 12 rebels, after they captured the village of Shuyukh near Jarabulus. During this time, ISIS had also captured the town of Karakozak, in Aleppo province near the Turkish border. The next day, the ISIS 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 ISIS fully retreated from Idlib and Latakia provinces.

On 16 March, according to local sources a number of foreign ISIS 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 ISIS withdrawal towards Margada town.

On 27 March, ISIS 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 ISIS took hold of these facilities, but were forced to withdraw after heavy clashes two days later. On 29 March, ISIS 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 ISIS in the fighting and many rebels were captured. The SOHR confirmed the death of at least seven ISIS fighters.

ISIS's Deir ez-Zor offensive
On 10 April, ISIS 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.

On 11 April, Jabhat al Nusra and Islamic battalions bolstered by reinforcements regained control of Abu Kamal after the ISIS was pushed out of occupied districts in less than a few hours after the takeover. ISIS pulled out to the T2 oil station on the outskirts of the city. Most of its checkpoints in the area were also removed.

On 13 April, fighting in the Kamal area subsided as ISIS retreated to the town of Haseen. Heavy clashes were reported with rebels as ISIS made territorial gains in the north, capturing several villages previously held by the rebels. On 16 April, rebels pulled away from North Deir ez-Zor. The same day, ISIS assassinated al-Nusra Emir in Idlib province, Abu Muhammed al Ansari. Four ISIS fighters were said to have entered his house, assassinating the commander and murdering his entire family. According to the SOHR, al Nusra rebels were alerted clashing with ISIS leaving the entire suicide team dead along with one rebel fighter.

By 26 April, according to rebel source, some 1,500 rebels were engaged in an offensive in Raqqa province, trying to push towards the city of Ar-Raqqa. The same source claimed that the rebels took at least five villages.

From 10 to 11 May, ISIS was said to have gained control of important parts of Eastern Deir ez-Zor province and districts of Deir ez-Zor city from rival rebel forces, opposition sources reported. On 13 May, ISIS reportedly gained control of at least five villages in the northern countryside of Al-Raqqa province after battles with rebels; 14 rebel fighters were reported killed in the clashes. ISIS was said to have executed the military commander of the Al-Raqqa rebel brigade and his nephew near Ayn Issa in Al-Raqqa province.

On 16 May, reports suggested that ISIS executed by beheading in Hama province a prominent brigade commander of the Islamic Front, Abu Miqdaam, who was known for destroying regime tanks.

By late May, 3,000 ISIS fighters were involved in the offensive in Deir ez-Zor.

On 22 May, ISIS was reported to have gained control of Al-Kharrat oil terminal in Deir ez-Zor province; 26 Al-Nusra and rebel fighters were killed in the fighting. ISIS was said to have captured five oil stations in the Deir ez-Zor countryside since the beginning of opposition infighting.

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

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

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

Over 21 and 22 June, ISIS 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.

On 25 June, the local unit of Al-Nusra in Abu Kamal on the Iraqi border pledged loyalty to ISIS.

On 29 June, ISIS executed and publicly crucified 8 rebel fighters in Aleppo province.

On 1 July, ISIS, bolstered by reinforcements from Iraq, routed rebels from Abu Kamal after days of fighting with opposition forces led by Al-Nusra. ISIS began advancing towards Al-Nusra's stronghold, Shuheil, also reported to be the hometown of its leader, Al-Golani.

On 3 July, ISIS took control of the towns of Mayadin and Shuhail in Deir ez-Zor province, after Al-Nusra fighters withdrew, and 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 ISIS. Following this, ISIS captured the villages of Quniya and Buqris, close to the town of Mayadin.

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

East Ghouta clashes
On 1 July, clashes erupted between Jaysh al-Islam and ISIS in the Eastern Ghouta town of Medaa. ISIS captured 25 of their fighters and executed an unknown number of them. On 2 July, Zahran Alloush, the Army of Islam's leader, gave an impassioned speech to his followers, deriding ISIS and listing several of their atrocities. On the same day, Army of Islamic claimed to have expelled ISIS from Medaa after a costly battle that led to the deaths of 14 fighters and claimed 15 ISIS casualties.

On 2 July, the rebel militia Islam Army reportedly expelled ISIS 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 IS after his car was destroyed by a roadside bomb in the Ghouta suburbs.

Following the ISIS 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 ISIS. The defection of Dawud is reported to have bolstered ISIS forces in Raqqa with more than a hundred combat vehicles, at least ten of them tanks.

On 21 July, SOHR reported that Al-Nusra Front seized a town from the Hazzm Movement in Idlib governorate. Therefore, Hazzm Movement said that it would no longer work with Al-Nusra Front.

Aleppo Offensive
On 13 August, 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 Aazaz. 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 the villages of Adeyyi and al Dahreyyi. On 27 August it was reported that rebels had 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.

On 7 September, the leader of the Syrian Revolutionaries Front, Jamal Maarouf, declared the start of a broader war against the Islamic State; he announced that the intent of the rebels is to clear IS forces from Aleppo, Raqqa and Deir Ezzor provinces.

Kobanê
In the summer of 2014, ISIS began taking over the area south of the Turkish border and then started to besiege the town of Kobanē. Multiple FSA factions, including the Grouping of the Dawn of Freedom Brigades and Liwa Thuwwar al-Raqqa have been involved in defending Kobanê against ISIS. The People's Protection Units have been cooperating with the Free Syrian Army in trying to defend Kobanê.

Attempted mediation
On 19 January, ISIS 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 ISIS 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 ISIS, however, it stated that it will retaliate if ISIS attacks first. In May 2014, ISIS 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.

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