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Non-international armed conflicts in Syria

Conflict type: Non-international armed conflict

There are multiple and overlapping non-international armed conflicts (NIACs) occurring in Syria. The Syrian Government and its allies are involved in NIACs against several rebel groups, including the Syrian National Army, Hay’at Tahrir al-Sham, the Islamic State group, the Syrian Democratic Forces and other smaller armed groups. Furthermore, there are also parallel NIACs between those armed groups operating in the territory. Finally, multiple NIACs are taking place between foreign state forces and armed groups on Syrian territory: two parallel NIACs between the US-led coalition on the one hand, and the Islamic State and Al-Qaeda on the other hand; two NIACs between Türkiye and respectively the Islamic State and Kurdish militia and, finally, a NIAC between Israel and Hezbollah.

There are multiple and overlapping non-international armed conflicts taking place in Syria.

  • Supported by Shia militias, Hezbollah, Russia, and the Wagner  Group, the Syrian government is involved in non-international armed conflicts against a wide array of rebel groups, namely the Syrian National Army (SNA) (former Free Syrian Army, FSA), Ahrar al-Sham, the Hay’at Tahrir al-Sham (former al-Nusra front), the Islamic State group, and the Syrian Democratic Forces (SDF, Kurdish militia). There are also parallel non-international armed conflicts due to the infighting between various armed groups, such as the Syrian National Army, the Islamic State group, Hay’at Tahrir al-Sham, Ahrar al-Sham, the Syrian Democratic Forces and other Islamist groups, such as Al-Qaeda and Hezbollah.
  • Without the consent of the Syrian government, an international coalition led by the United States initiated airstrikes against the Islamic State group and al-Qaeda affiliates in a spill over from the conflict against these groups in Iraq.
  • Türkiye is also involved in the non-international armed conflict against the Islamic State group. Moreover, Türkiye has been targeting Kurdish militia inside Syria and deployed ground troops in northern Syria, leading to a military occupation of part of northern Syria.

Two criteria need to be assessed in order to answer the question whether a situation of armed violence amounts to a non-international armed conflict.

  • First, the level of armed violence must reach a certain degree of intensity that goes beyond internal disturnaces and tensions.
  • Second, in every non-international armed conflict, at least one side to the conflict must be a non-state armed group which must exhibit a certain level of organization in order to qualify as a party to the non-international armed conflict. Government forces are presumed to satisfy the criteria or organization. For further information, see 'non-international armed conflict' in our classification section.

Intensity of violence

Various indicative factors are used to assess whether a given situation has met the required intensity threshold, such as the number, duration, and intensity of individual confrontations; the types of weapons and military equipment used; the number of persons and types of forces participating in the fighting; the number of casualties; the extent of material destruction; the number of civilians fleeing; and the involvement of the United Nations Security Council. For further information, see 'non-international armed conflict - intensity of violence' in our classification section.

The initial phase of the Syrian conflict took place between March and July 2011. After protests started in March 2011, the government of President Assad deployed the armed forces for the first time in April 2011. Faced with an increasingly violent response by security and military forces, the protests spread across the country during 2011. M. Slackman, ‘Syrian troops open fire on protesters in several cities’, The New York Times, 25 March 2011; ‘‘Deadliest day’ in Syria uprising’, Al Jazeera, 23 April 2011.

The beginning of the NIACs between the government and rebel groups can be traced back to July 2011. Although the first armed confrontation occurred in June 2011, when rebels killed approximately 120 – 140 Syrian security personnel , the clashes with the first newly formed and organized rebel group Free Syrian Army were reported during September and October 2011. ‘‘Free Syrian Army’ poses growing threat to Assad’France24, 14 October 2011; ‘Cracks in the army’The Economist, 29 October 2011. Clashes continued during the following year and have never ceased. Notably, in its February 2012 Report the United Nations Independent Commission of Inquiry documented bombings and shelling ‘with heavy weapons, leading to massive casualties and the destruction of homes and infrastructure.’ UN Human Rights Council, Report of the Independent International Commission of Inquiry on the Syrian Arab Republic, 22 February 2012, A/HRC/19/69. Sieges accompanied by heavy shelling before ground clearance operations became a regular feature of the government’s strategy. The escalating violence led to rapidly raising numbers of Syrian refugees and tens of thousands of internally displaced people. ‘As Syria bleeds, neighbors brace for refugees’Reuters, 10 February 2011.

In early 2012, Kofi Annan started the negotiations for a peace plan (including provisions for a ceasefire). However, clashes between the armed forces and rebel militias continued, including alleged violations of IHL and Human Rights Law. Amnesty International, Deadly Reprisals, deliberate killings and other abuses by Syria’s armed forces, 14 June 2012. After the failure of a UN-brokered peace plan and ceasefire in June 2012, the hostilities spread to previously relatively insulated areas surrounding Damascus and Aleppo. With the fighting intensifying beyond the three initial hotspots of Idlib, Homs, and Hama, the ICRC announced in July 2012 that the violence in Syria had reached the threshold of a non-international armed conflict. ICRC, Syria: ICRC and Syrian Arab Red Crescent maintain aid effort amid increased fighting, 17 July 2012. However, others have argued that the threshold to an armed conflict was reached earlier in 2012. K. Huszti Orban and N. Kalandarishvili-Mueller, ‘Is it a Bird? Is it a Plane? Is it an Armed Conflict? – The Classification of the Situation in Syria’ (2012)  and Laurie R. Blank and Geoffrey S. Corn, ‘Losing the Forest for the Trees: Syria, Law and the Pragmatics of Conflict Recognition’ (2013) Vanderbilt Journal of Transnational Law.

As of January 2018, the Independent International Commission of Inquiry on the Syrian Arab Republic reported 34 chemical attacks since 2013. In April 2018, a chemical attack took place in the Suburb of Douma. The World Health Organization confirmed the death of 70 people due to ‘highly toxic chemicals.’ D. Victor, ‘Suspected Chemical Attack in Syria: What we know and don’t know’, The New York Times, 11 April 2018. 

The intensity of violence is further confirmed by the effects of the conflict on the civilian population. In 2021, after 10 years of conflict, 6.7 million Syrians are reported to be internally displaced, while 6.6 million Syrians live as refugees worldwide (especially in Lebanon, Türkiye, and Jordan). UNHCR, Syria emergency. The United Nations Office for the Coordination of Humanitarian Affairs (OCHA) confirms that at the end of 2020 there were at least 11.1 million people who need humanitarian assistance due to the conflict. This includes 4.7 million people in acute need. OCHA, Syrian Arab Republic. Up to 2021, which marked 10 years since the breakout of the conflict in Syria, over half a million people have been killed, including 55,000 children. Almost 5 million children in Syrian have been born into war and half of the Syrian population have fled from their homes. The spread of the COVID-19 pandemic highly exacerbated the immense humanitarian crisis already occurring in the Country. ReliefWeb, ‘10 years on: 10 facts that explain Syria’s conflict’, 15 March 2021.

Islamic State (IS)

On June 25, 2014, Iraq sent a letter to the United Nations Security Council (UNSC), where it asked for international ‘support in order to defeat’ the Islamic State (IS). Letter dated 25 June 2014 from the Permanent Representative of Iraq to the United Nations addressed to the Secretary-General, UN Doc. S/2014/440 (2014). On August 7, 2014, the US began airstrikes against ISIS in Iraq and soon thereafter launched operation ‘Inherent Resolve’: a multinational military campaign aimed at defeating ISIS in Iraq. V. Koutroulis, ‘The Fight against the Islamic State and Jus in Bello’ (2016) 29 Leiden Journal of International Law 827, 830. In September 2014, a US-led coalition extended the strikes against ISIS on Syrian territory. At first the intervention was conducted by the US, Bahrain, Jordan, Qatar, Saudi Arabia, and the United Arab Emirates. Albeit initially reluctant, Australia, Canada, France, and the UK, among others, eventually joined the US-led coalition intervening in Syria. Olivier Corten, ‘Military Operations against ‘Islamic State’ (ISIL or Dae'sh) – 2014’ in Tom Ruys, Olivier Corten and Alexandra Hofer (eds.), The Use of Force in International Law: A Case-based Approach (Oxford University Press 2018) 873, 875-876; Olivia Flasch, ‘The Legality of the Air Strikes against ISIL in Syria: New Insights on the Extraterritorial Use of Force against Non-State Actors (2016) 3 Journal on the Use of Force and International Law 37, 38; Koutroulis, ‘The Fight against the Islamic State’ (n 2), 835. The following year, Russia militarily intervened in Syria upon invitation of President Assad. Letter dated 15 October 2015 from the Permanent Representative of the Russian Federation to the United Nations addressed to the President of the Security Council, UN Doc. S/2015/792 (2015). As the US-led coalition intervened without the consent of the Syrian government, the States of the coalition are party to a NIAC against the IS and an IAC against Syria. On the contrary, since Russia has intervened upon invitation of Assad, there is no IAC between the two countries. 

On November 20, 2015, the UNSC unanimously adopted resolution 2249 (2015), where it ‘called upon member States … to take all necessary measures … on the territory under the control of ISIL … to prevent and suppress terrorist acts committed specifically by ISIS … and to eradicate the safe haven they have established over significant parts of Iraq and Syria.’ UN Doc. S/RES/2249 (2015), 20 November 2015. Since then, ISIS’ territorial control over Syria and Iraq has decreased dramatically and on March 23, 2019, it lost the last part of territory it controlled in Syria. ‘IS 'caliphate' defeated but jihadist group remains a threat’, BBC News (23 March 2019).

In March 2017, supported by Russia, the Syrian forces recaptured the ancient desert town of Palmyra from the Islamic State group. M. Chulov, ‘Syrian regime recaptures Palmyra from Islamic State’, The Guardian, 2 March 2017. Between 2013 and 2017 several armed confrontations occurred between the IS and Kurdish armed groups in Syria. In September-December 2018, Kurdish forces launched an attack against the IS in Syria, reducing its territory to a small enclave next to the Iraqi border. ‘Syria prfofile – timeline’, BBC News, 14 January 2019. Consequently, the US withdrew almost all its troops from the northern part of Syria. Former US President Donald Trump declared to have won against IS. M. Landler, H. Cooper and E. Schmitt, ‘Trump to withdraw U.S. forces from Syria, declaring ‘we have won against ISIS’’, The New York Times,  19 December 2018. However, between 2019 and 2021 IS continued to perpetrate deadly attacks in Syria (including against U.S. military personnel). Clashes between the IS and Kurdish groups operating in Syria also continued and in March 2019 Kurdish-led forces captured IS’ last holdout. More recently, in February 2021 IS continued to carry out attacks in the central desert, which were responded to with Russian airstrikes in support of the government army. International Crisis Group, Crisis Watch. IS is still active despite its lack of territory, as shown by its large-scale attack on the Ghwayran/al-Sina'a prison in al-Hasakah in 2022. In its attempt to free fighters, violent clashes with the Syrian Democratic Forces (SDF) and the U.S. coalition resulted in hundreds of deaths. Mohammed Hassan and Samer al-Ahmed, ‘A closer look at the ISIS attack on Syria’s al-Sina prison’, Middle East Institute, 14 February 2022; International Crisis Group, Crisis Watch, February 2021 - April 2022. After the prison attack, IS significantly stepped up its activities in Syria by attacking military targets in the central desert, killing dozens of SDF and government troops. International Crisis Group, Crisis Watch, February 2022 - April 2022. In the past 10 years of the conflict, IS has killed approximately 5.000 civilians. Syrian Network for Human Rights, Civilian Death Toll.

Syrian National Army (SNA), former Free Syrian Army (FSA)

The beginning of the armed insurrection in Syria is typically marked by the foundation of the FSA (Free Syrian Army). ‘Guide to Syrian rebels’, BBC News, 13 December 2013. The group’s main purpose was to defeat Assad’s regime in Syria. After the first period of clashes in 2011, the FSA entered into a period of ceasefire in April 2012 which, however, collapsed a few months later, leading to sustained armed offences conducted by the group against government forces. M. Weaver and B. Whitaker, ‘Syria accepts ceasefire with conditions – Thursday 25 October 2012’The Guardian, 25 October 2012.

In 2014, tensions between the FSA and the IS in Syria emerged, most notably over territorial control. ‘FSA hit back at ISIS in east Syria province’, Al Arabia News, 28 June 2014 ;   ‘FSA-ISIS fighting kills 51 on Syria-Iraq border’Al Arabiya News, 10 April 2014. The Aleppo battle in 2016 was a firm factor in the Syrian civil war. In December 2016, the Syrian government and allied militias recaptured the city from opposition forces, making it the biggest military win to the Syrian government since the war started. ‘Aleppo: Key dates in battle for strategic Syrian city’, BBC News, 13 December 2016; ‘AFP, Syria’s war: major regime victories’, Gulf News, 8 July 2018. In May 2017, the Syrian government in a major defeat to the opposition group recaptured Homs, the capital of the Syrian revolution. As a result, the Free Syrian Army lost control of significant parts of the territory. J. Ensor, ‘Syria’s ‘capital of revolution’ Homs fall under complete control of Assad government’The Telegraph, 22 May 2017. During the same month, Russia, Iran, and Türkiye signed an agreement to create ‘de-escalation zones’ to stop hostilities between Syrian government forces and allies against rebel groups. The deal created four zones, located respectively in Idlib province, in the Rastan and Talbiseh enclave in northern Homs province, in Eastern Ghouta in the northern Damascus countryside, and the rebel-controlled South along with the border of Deraa and Quneitra province. ‘Syria’s ‘de-escalation zones’ explained’, Al Jazeera, 4 July 2017.

In 2017 and 2018, the FSA continued major offensives against government-controlled areas and the IS. International Crisis Group, Crisis Watch. The FSA graduated into the larger Syrian National Army (SNA) in 2019. C. Kasapoglu, ‘The Syrian National Army and the Future of Turkey’s Frontier Land Force’The Jamestown, 12 March 2021. The group, supported by Turkish forces, has conducted a number of operations against the Kurdish Protection Units (YPG) and the Syrian Democratic Forces (SDF). For instance, an operation led by Türkiye and the SNA was launched in 2019 against the SDF. L. Pitarakis and S. El Deeb, ‘Turkey begins bombing and shelling Kurdish fighters after American soldiers pull back; Trump calls operation ‘bad idea’’Chicago Tribune, 9 October 2019. Additional clashes involving the SNA and the SDF occurred in the period between the end of 2020 and the beginning of 2021 in the Raqqa Governorate. ‘Clashes with Turkey-backed militias continue in Ain Issa: SDF’, RUDAW, 19 December 2020. In 2020, the group engaged in armed confrontations against the governmental troops in Daraa. T. Rollins, ‘Unrest in south-west Syria erupts into urban warfare’, The National, 8 March 2020.

In the course of 2021, these confrontations extended to the Hasakah Governorate and hostilities involving the SNA were also reported in the Allepo Governorate. International Crisis Group, Crisis Watch, August 2021. In February 2022, YPG launched a rocket attack at Azaz, which is an SNA controlled area in the Allepo Governorate. In response, the SNA attacked YPG positions in Tal Rifaat. Omer Koparan, ‘TPG/PKK rocket attack kills 4 civilians in Aza, Syria’, AA, 15 February 2022; International Crisis Group, Crisis Watch, February 2022. There are also continuing confrontations with government forces. In April 2022, for instance, there were reports of such confrontations. Ghaith Alsayed, ‘Shelling of rebel village in northern Syria kills 4 students’, AP News, 4 April 2022; International Crisis Group, Crisis Watch, April 2022.

Hay’at Tahrir al Sham (HTS)

Clashes between the group against the Syrian government and other armed rebels such as IS and al-Qaeda, were reported to have occurred in the past years (accordingly from 2017 to 2021). More recently, in 2021, the group was allegedly responsible for the killing of at least 16 members of the al-Qaeda group. International Crisis Group, Crisis Watch. By the end of 2021, HTS launched an offensive against opposing jihadist groups, in particular: Jund Allah. As a result of this crackdown, they seized control of Tal al-Mashafa, Tal al-Abraj, Tal Abu Afer and Salour, in and around the provinces of Idlib and Latakia. Khaled al-Khateb, ‘Syrian jihadi group cracks down on last pocket of rivals in Idlib’, Al-Monitor, 1 November 2021; International Crisis Group, Crisis Watch, November 2021. In late 2021, government forces stepped up their military action against the HTS, fearful of their increased power and governance in and around Idlib. Khaled al-Khateb, ‘Syrian government steps up attack against Islamist enclave’, Al-Monitor, 19 January 2022.

In October 2022, HTS advanced into Afrin city and clashed with Turkish-backed coalition of armed groups Syrian National Army, but eventually withdrew and seized control of Kafr Jana, resulting in dozens of people killed. Fighting ended when Turkish troops were deployed around Kafr Jana. HTS also began ground operations against regime forces in September 2022 and has carried out raids in Idlib and Latakia provinces as of March 2023. On 23 March 2023, 10 were killed in a clash between HTS and the regime in northern Aleppo province. International Crisis Group, Crisis Watch: Syria.

The Syrian Democratic Forces (SDF)

SDF vs Syria

In 2018, the SDF and Syrian government forces clashed over four villages in Deir ez-Zor that resulted in 6 SDF fighters dead. SDF clash with Syrian regime forces in Deir ez-Zor’, Rudaw, 29 April 2018. During the first half of 2021, the SDF has clashed with the Syrian government . The SDF and regime forces clashed in March 2022 resulting in 2 regime soldiers killed and 2 SDF fighters killed. It is rare for SDF and Syrian forces to engage in confrontation. International Crisis Group, Crisis Watch: Syria; ‘4 dead in rare Syria-Kurdish clash: monitor’, Al-Monitor, 1 March 2022. In April 2022, in response to the YPG-controlled al-Ashrafiyyah and Sheikh Magsoud neighbourhoods being sieged by regime affiliated militia, the YPG-led SDF tightened their siege by taking over more government offices and closing the highway in Qamishli. International Crisis Group, Crisis Watch: Syria. In 2023, there was a clash between Syrian government forces and an SDF-linked fighter in Deir ez-Zor, It still remains the exception for there to be clashes between pro-Syrian governments forces and SDF-linked fighters, with clashes being concentrated in Hasakah and Qamishlo. W. van Wilgenburg, ‘Fatal clash between SDF and Syrian army prompts SDF investigation’, Kurdistan24, 13 April 2023.


Since 2017, the SDF has also been involved, supported by the U.S.-led coalition, in military raids against ISIS and in the heavy clashes following ISIS’s attack on the Ghwayran/al-Sina’a prison in January 2022. International Crisis Group, Crisis Watch, December 2021 – February 2022; O. Qereman, ‘Syria Kurds halt joint ops with U.S.-led coalition after Turkish raids’, Reuters, 2 December 2022. In 2022, the U.S.-led coalition and the SDF continued the fight against ISIS conducting 108 partnered operations and 150 raids in an 8-day operation that occurred from 28 December 2022 to 5 January 2023. State of U.S. Campaign Against ISIS’, Wilson Center, 12 January 2023. The U.S. coalition and SDF have continued fighting ISIS in the north Easter in 2023. International Crisis Group, Crisis Watch: Syria.

SDF v Türkiye

I early October 2019, Türkiye conducted an offensive in Syria called Peace Operation Spring, following which a deal was concluded between Russia and Türkiye, whereby the SDF removed troops away from the Turkish-Syrian border and were replaced by Syrian forces and joint patrols by Russia and Turkey. SDF begins withdrawal from Syria-Turkey border’, Al Jazeera, 27 October 2019; U. Uras, ‘Turkey’s Operation Peace Spring in northern Syria: One month on’, Al Jazeera, 8 November 2019. In the course of 2021, regular confrontations took place between the SDF and Turkish-backed armed groups. International Crisis Group, Crisis Watch, December 2021 – February 2022. During the month of August 2022, there were cross-border attacks between Türkiye and the SDF and Türkiye and the Syrian army. Türkiye launched drone strikes in October 2022 killing a YPG commander and again in January 2023, targeting YPG. International Crisis Group, Crisis Watch: Syria. Türkiye’s attack in December 2022 in the town of Ain Issa killed 5 SDF fighter in a pattern of daily attacks against SDF fighters. SDF announces death of five fighters by Turkey in northern Syria’, Rudaw, 10 December 2022. In May 2023, in a suspected drone attack by Türkiye in Hasaka province, 3 SDF fighters were killed. Again, this drone attack was part of a string of attacks by Türkiye. K. Dri, ‘SDF says two fighters killed by Turkish drone in Hasaka’, Rudaw, 5 May 2023.

Ahrar al-Sham

In May 2015 the group (together with other rebel forces, including Jabhat al-Nusra) captured Mastoumeh village and Ariha. In 2015, 2016 and 2017, the group clashed with other rebel groups operating in Syria, including IS, Hezbollah, Nusra front and Hay’et Tahrir al Sham (HTS). More tensions arose in 2020 between the HTS and the Ahrar al-Sham. International Crisis Group, Crisis Watch. However, no significant attacks by Ahrar al-Sham have been reported since 2019. ‘Mapping militant organizations: Ahrar al-Sham’, Center for International Security and Cooperation, March 2022. Therefore, it is possible to conclude that the situation does not amount to a NIAC anymore.


A long-time ally of the government in Syria, Hezbollah confirmed in May 2013 that it had sent fighters to support President Assad. S. G. Jones, ‘The Escalating Conflict with Hezbollah in Syria’, CSIS, 20 June 2018. Since then, fighting has been continuing, including those involving Israeli armed forces. S. Al-khalidi, ‘Israel intensifying air war in Syria against Iranian encroachment’, Reuters, 22 April 2021. Israel regularly conducted airstrikes against Hezbollah-related targets on Syrian territory. Seth G. Jones and Maxwell B. Markusen, ‘The escalating conflict with Hezbollah in Syria’, Center for Strategic and International Studies, 20 June 2018. After fighting in alliance with the Syrian regime for 8 years, in July 2019 Hezbollah confirmed that it began repositioning troops back closer to the Lebanese border, while still maintaining a minimal presence across Syria. Hezbollah withdraws troops from Syria to the Lebanon border’, Middle East Monitor, 16 July 2019; K. Robinson, ‘What is Hezbollah’, Council on Foreign Relations, 25 May 2022.


A series of indicative factors are used to assess whether armed groups exhibit the required degree of organization, such as the existence of a command structure and disciplinary rules and mechanisms, the ability to procure, transport, and distribute arms, the ability to plan, coordinate and carry out military operations, the ability to negotiate and conclude agreements, e.g. cease fire or peace agreements. If the criterion of a minimum organization of the armed group is not fulfilled, there is no non-international armed conflict. For further information, see 'non-international armed conflict - organization' in our classification section.

The armed conflicts tend to be very localized. A multitude of armed groups operate in different areas to a varying degree, sometimes cooperating with each other, sometimes fighting each other. Alliances are fluid and frequently shifting, contributing to the frequent emergence and disappearance of armed groups or mergers between armed groups. For a mapping of the major Syrian militant organizations that have been operating since 2011, see Stanford University, ‘Mapping Militant Organizations: Syria’, 26 August 2016. In opposition held areas, local administrative councils usually depend on armed groups and their enforcement powers and some local administrative councils are dominated by armed groups. See B. Hajjar, C. von Burg, L. Hilal, M. Santschi, M. Gharibah and M. Sharbahi, ‘The Experience of Local Administrative Councils in Opposition-held Syria’, Swiss Peace, January 2017.

Far from being a unified movement, the Syrian armed opposition is highly fragmented with several overlapping non-international armed conflicts between armed groups and the Syrian government, but also between such armed groups. See also T.D. Gill, ‘Classifying the Conflict in Syria’, U.S. Naval War College, 92 International Law Studies, pp 354 – 361.  The armed conflicts tend to be very localized. A multitude of armed groups operate in different areas to a varying degree, sometimes cooperating with each other, sometimes fighting each other. Alliances are fluid and frequently shifting, contributing to the frequent emergence and disappearance of armed groups or mergers between armed groups.

Islamic State group

First, the most important armed group is the Islamic State group, also known as the Islamic State of Iraq and al-Sham / the Levant (ISIS or ISIL) and Da’esh. The Islamic State group fights against government forces and other rebel groups. The Islamic State group grew out of the Islamic State of Iraq, an umbrella organization formed by various Sunni insurgency groups in 2006 and dominated by al-Qaeda in Iraq. In 2012, the group expanded its activities into Syria and helped set up the Syrian al-Qaeda affiliate Jabhat al-Nusra. After both Jabhat al-Nusra and the leadership of al-Qaeda rejected the Islamic State group’s attempt to merge with Jabhat al-Nusra in spring 2013, the group began operating under the name of Islamic State of Iraq and al-Sham (ISIS) in both Iraq and Syria. For further information, see Standford University, Mapping Militant Organizations: The Islamic State, 23 October 2017. Simmering tensions between the Islamic State group and other rebel groups erupted into open conflict from January onwards when a broad array of rebel groups launched attacks to expel ISIS from various towns across Syria. L. Morris, ‘Stretched thin, Syrian Extremists Are Pressured', The Washington Post, 7 January 2014. After an unsuccessful call to end the infighting, al-Qaeda leader Ayman al-Zawahri disavowed all links with the Islamic State group in February 2014. ‘Al-Qaeda Disowns ISIL Rebels in Syria', Al Jazeera, 3 February 2014. The group changed its name to Islamic State after taking control over Mosul in June 2014. Research into the structure of the Islamic State group reveals that, in addition to its military structure and operations, the group includes a complex structure for the administration of the territories it controls. A. Al-Tamimi, ‘The Evolution in Islamic State Administration: The Documentary Evidence’, 9 Perspectives on Terrorism 4 (2015); N. Thompson and A. Shubert, ‘Anatomy of ISIS’, CNN, 14 January 2015; C. Reuter, ‘Secret Files Reveal the Structure of the Islamic State’, Spiegel Online, 18 April 2015; R. Barrett, The Islamic State, The Soufan Group, November 2014. Throughout 2016 and 2017, the Islamic State group lost territory in Syria and Iraq. For interactive maps showing the evolution of territorial control in Syria, see ‘Islamic State and Crisis in Iraq and Syria in Maps’, BBC, 18 January 2018 and S. Asrar, 'Syria: Who Controls What?', Al Jazeera, 29 November 2017 , and the constantly updated maps by liveuamaps for Syria and the syrian civil war map. See also Fourth Report of the Secretary-General Pursuant to Paragraph 7 of Resolution 2233 (2015), UN doc S/2016/592, 5 July 2016; Global Conflict Tracker: War Against Islamic State in Iraq, Council on Foreign Relations. Backed by the U.S.-led coalition, the Syrian Democratic Forces, an alliance of rebel groups led by the Kurdish Protection Units YPG, captured Raqqa, the capital of the Islamic State groups' self-proclaimed caliphate, in October 2017. However, the Islamic State group continues to control territory, namely in the estern province of Deir al-Zor and continues to be able to sustain military operations.  For maps showing who controls what in Syria, see S. Asrar, 'Syria: Who Controls What?', Al Jazeera, 29 November 2017; 'Islamic State and the Crisis in Iraq and Syria in Maps', BBC, 10 January 2018;  'Syria War: UN Says It Is Ready to Go Into Raqqa', BBC News, 18 October 2017; T. Perry, L. Barrington, 'U.S.-Backed Campaign Against IS in Eastern Syria to Speed Up - SDF Militia', Reuters, 18 October 2017; M. Petkova, 'What Will Happen to Post-ISIL Raqqa?', Al Jazeera, 17 October 2017 .

In March 2017, with support of Russian jets, the Syrian forces recaptured the ancient desert town of Palmyra from the Islamic State group. ‘Syrian regime recaptures Palmyra from Islamic State’, The Guardian, 2 March 2017. The Syrian Democratic Forces (SDF) have pushed the Islamic State out of Deir el-Zour after an assault. ‘Islamic State driven out of Deir el Zor as group loses ground in Syria and Iraq’, Sky News, 3 November 2017. Moreover, the leader of the Islamic State group Abu Bakr al-Baghdadi allegedly committed suicide in Syria in October 2019, during a US-led raid.  In addition, on 3 February 2022, a U.S. special forces raid caused the death ISIS leader Abu Ibrahim al-Hashimi al-Qurayshi and several other ISIS fighters. ‘Kurdish-led forces in Syria recapture prison from ISIL’, Al Jazeera, 26 January 2022; ‘Islamic State leader Abu Ibrahim al-Qurayshi killed in Syria, US says’, BBC, 4 February 2022; International Crisis Group, Crisis Watch, January - February 2022. ISIS has lost several leaders including ISIS leader Abu al-Hasan al-Hashmi al-Qurayshi in November 2022 who was killed in an operation by the FSA and was replaced by Abu al-Husain al-Husaini al-Quraishi. In addition, several senior leaders including Hamza al-Homsi in February 2023 and in April 2023, the US killed senior leaders Abd-al-Hadi Mahmud al-Haji Ali in northern Syria and Khalid Aydd Ahmad al-Jabouri. E. Kourdi, ‘ISIS acknowledges the death of its leader, announces his successor’, CNN, 30 November 2022; ‘US military: Senior ISIL leader killed in Syria helicopter raid’, Al Jazeera, 17 April 2023; ‘ISIL leader killed, 4 US troops injured in Syria raid: Pentagon’, Al Jazeera, 17 February 2023.

Syrian National Army (SNA), former Free Syrian Army (FSA)

Formed by deserters from the Syrian armed forces in July 2011, the Free Syrian Army is a loose alliance of rebel groups that fight against both the government of President Assad and the Islamic State group. In 2012, the group established a Code of Conduct. The Code of Conduct is available in the Geneva Call Database Their Words. Directory of Armed Non-State Actor Humanitarian Commitments,  'Code of Conduct of the FSA', 2012.  The Free Syrian Army also made several unilateral statements, for example calling for the demilitarization of schools and hospitels. See Geneva Call, Their Words, Directory of Non-State Actor Humanitarian Commitments, 'Free Syrian Army', 2016. In July 2017, four of its brigades signed Geneva Call's Deeds of Comittiment prohibiting the use of child soldiers and sexual violence. Geneva Call, 'Syria: 4 Brigades of the Free Syrian Army Commit to Prohibit Sexual Violence and the Use of Child Soldiers', News, 3 July 2017. 

While it is difficult to identify the components of the FSA and assess their relative strength, rebel groups under the banner of the FSA continue to be involved in the hostilities. For example, Free Syrian Army affiliates joined the battle for Kobane in 2014, captured the city of Bosra al-Sham in March 2015 and participated in the offensive to expel the Islamic State group from Jarablus in August 2016. Abo Bakr al Haj Ali, ‘FSA Take Control of Ancient City in Southern Syria’, Middle East Eye, 26 March 2015; A. Barnard, ‘Knowing the Risks, Some Syrian Rebels Seek a Lift From Turks’ Incursion’, The New York Times, 29 August 2016. Turkey backs and fights along the Free Syrian Army, in particular along the Turkish border region. S. Al-Khalidi, 'Turkish Army Expands Deployment in Syria's Northwest: Rebels', Reuters, 15 October 2017.  In January 2018, the Free Syrian Army supported the Turkish offensive against Afrin, a region controlled by Kurdish forces. 'Turkey Deploys Thousands of FSA Rebels at Syria Border', Al Jazeera, 20 January 2018.

In 2012, the FSA created The Supreme Military Council (SMC, also know as the Council of Thirty) in an attempt to form a command structure among its brigades. However, tension arose in the SMC after a group of FSA leaders tried to replace SMC Leader General Salim Idriss. As a result, the FSA’s National Coalition for Syrian Revolutionary and Opposition Forces (National Coalition) ordered the SMC to dissolve in June 2014. Since the SMC’s dissolution, it has been unclear if the FSA has an established command structure. However, media outlets generally cite the FSA as an established group. Prominent FSA brigades include the 1st Coastal Division, Yarmouk Army, and the Northern Sun Battalion. See Stanford University, ‘Mapping Militant Organizations: Syria’, 26 August 2016.

With regard to territorial control, up to 2015 the Free Syrian Army controlled many territories in Syria. However, over the past several years the FSA lost control over most territories to the Syrian government and it is allies. S. Elwazer, ‘Syrian government troops retake Rabia, last rebel stronghold in Latakia’, CNN, 25 January 2016.

Hay’at Tahrir al Sham

Set up in 2011 by the al-Qaeda operative al-Jawlani, Jabhat al-Nusra aims to overthrow the government of President Assad. In 2016, the group changed its name to Jabhat Fatah al-Sham and announced its split from al-Qaeda. See L. Sly and K. DeYoung, ‘Syria’s Jabhat al-Nusra Splits from al-Qaeda and Changes its Name’, The Washington Post, 28 July 2016. Its relationship with other rebel groups is complicated, sometimes cooperating with them, especially on a local level, sometimes attacking them. M. Chulov, ‘US Plan for Proxy Army to Fight ISIS in Syria Suffers Attack’, The Guardian, 2 September 2014. For further information on the group, see Stanford University, Mapping Militant Organizations. Jabhat Fatah al-Sham (Formerly Jabhat al-Nusra), 25 August 2016.  Initially, they reportedly cooperated with Ahrar al-Sham in attacks against the Syrian armed forces, B. Hubbard, ‘In Syria, Potential Ally’s Islamist Ties Challenge U.S.’, The New York Times, 25 August 2015. Ahrar al-Sham, founded by Islamists after their release from Syrian prions as part of an amnesty in spring 2011, is considered one of the largest and most powerful rebel groups. Led by Ali al-Omar, the group is also involved in the hostilities against the Islamic State Group. Stanford University, Mapping Militant Organizations. Ahrar al-Sham,  5 August 2017. However, cooperation between the two alliances reportedly ended in January 2017 when several armed militia joined Ahrar al-Sham and Jabhat Fatah al-Sham formed a new alliance with other extremist factions, called Hay'et Tahrir al Sham (HTS), against its former ally, Conference Room Paper of the Independent International Commission of Inquiry on the Syrian Arab Republic, UN doc A/HRC/34/CRP.3, 10 March 2017, §9 and footnoe 14; see also Standford University, Mapping Militant Organizations. Hay'at Tahrir al-Sham (Formerly Jabhat al-Nusra), 14 August 2017.  After a period of fighting between the two groups, Report of the International Commission of Inquiry on the Syrian Arab Republic, UN doc A/HRC/36/55, 8 August 2017, §13. HTS reporteldy ejected Ahrar al-Sham from Idlib in August 2017. H. Haid, 'Why Ahrar al-Sham Couldn't Stand Up to HTS's Attack in Idlib', Chatham House, 17 August 2017.

The Syrian Democratic Forces, in particular the Kurdish Protection Units (YPG)

Kurdish Protection Units (YPG) assumed control over the Kurdish areas in north-eastern Syria, namely Rojava, following the withdrawal of the Syrian army in summer 2012. Widely believed to be the armed wing of the Kurdish Democratic Unity Party, its leader claims that the YPG includes about 10’000 fighters. Little is known about its organization, but they seem to have a unified command and control structure. ‘Interview mit Salih Muslim: Es gab keinen Kurden-Deal mit dem Regime’Frankfurter Rundschau, 1 December 2012. In 2012, all female units known as the Women's Protection Units YPJ were set up. 'YPJ: The Kurdish Feminists Fighting Islamic State', The Week, 7 October 2014. N. Tavakolian, 'Meet the Women Taking the Battle to ISIS', Time, 2 April 2015. Both the YPG and the YPJ signed Geneva Call's Deeds of Commitment to prohibit the use of anti-personnel mines, the sexual violence and gender discrimination and the use of child soldiers, which further illustrates their degree of organization. Geneva Call, 'Syrian Kurdish Armed Non-State Ctors Commits to Ban Anti-Personnel Mines, Sexual Violence and Child Recrutiment', News, 16 June 2014. The Deeds of Committment are available in the Geneva Call Database Their Words. Directory of Armed Non-State Actor Humanitarian Commitments, 'YPG/YPJ', 2014. In 205, the general command of the YP issued a circular  reminding its recruiting centers and leaders to abstain from recruiting children. Backed by the United States, the Kurdish Protection Units have been fighting against the Syrian government and other armed groups, in particular the Islamic State group. R. Said, 'Kurdish Militia Launches Assault to Evict Syrian Army from the Key City of Hasaka’, Reuters, 22 August 2016; ‘Syrian Kurds’ Drive Islamic State out of Kobane', BBC, 26 January 2015.  They dominate the Syrian Democratic Forces, an umbrella group composed of Kurdish and Arab rebel groups. E. Schmitt, 'U.S.-Backed Militia Opens Drive on ISIS Capital in Syria', The New York Times, 6 November 2016; Conference Room Paper of the Independent International Commission of Inquiry on the Syrian Arab Republic, UN doc A/HRC/34/CRP.3, 10 March 2017, §86.  In May 2017, the United States started to provide weapons to the Kurdish milita. P. Cockburn, 'Donald Trump's Decision to Arm Kurdish Fighters Could Have Profound Impact on the Syria Crisis', The Independent, 10 May 2017; P. Stewart, 'U.S. Starts Providing Weapons to Syrian Kurds', Reuters, 30 May 2017. In October 2017, the Syrian Democratic Forces captured Raqqa, the self-proclaimed capital of the Islamic State group's caliphate.T. Perry, L. Barrington, 'U.S.-Backed Campaign Against IS in Eastern Syria to Speed Up - SDF Militia', Reuters, 18 October 2017; M. Petkova, 'What Will Happen to Post-ISIL Raqqa?', Al Jazeera, 17 October 2017.

In May 2018, the Syrian Democratic Forces announced operation Al-Jazeera Storm against remnants of the Islamic State in Iraq and the Levant (ISIL) after they had regrouped along the border between the Syrian Arab Republic and Iraq. In December 2018, they recaptured Hajin the last stronghold of ISIS in Syria. R. Hussein, Z. Omar, ‘US, Allies Warn Syria as a New Offensive Begins’, Voanews, 02 May 2018, M. Chulov, ‘ISIS withdraws from last urban stronghold in Syria’, The Guardian, 14 December 2018.

After the incursion by Türkiye in October 2019, the SDF has lost territory but remained in control of Manbij, Raqqa, the Kobane region, and parts of Hasakah province, in addition to Syria’s main energy-rich regions. Russia and the Syrian regime are present in SDF-held territory in part to stop Türkiye. W. van Wilgenburg, ‘Syrian Democratic Forces (Syria)’, European Council on Foreign Relations.

Ahrar al-Sham

Ahrar al-Sham, also known as Harakat Ahrar al-Sham al-Islamiyya, or the Islamic Movement of the Free Men of the Levant, is a Sunni militant group operating in Syria. The group’s aim is to overthrow the Syrian regime and establish an Islamic government. The group conducted it is first attack in November 2012. Currently, the group is present in Idlib province. The leader of the group was Abu al-Yaqzan between 2013 and 2016. Over the past years the group has allied, occasionally, with the Islamic State (IS) and with Hay’at Tahrir al-Sham. Ahrar al-Sham profile, ‘Mapping Militant Organization’, Standford University, 5 August 2017.

A number of countries have intervened in Syira since the beginning of the armed conflict that has been opposing the government to rebel groups. Notably, the US-led coalition, Türkiye, and Israel have intervened without the consent of Syria, hence triggering parallel IACS. For an analysis of these interventions, see RULAC, International Armed Conflicts in Syria. On the other hand, Russia has intervened upon invitation of the Syrian government.


In September 2015, Russia intervened upon invitation of the Syrian government. Russia’s military presence assisted the Syrian governmental forces in taking over East Aleppo in November 2016, along with the establishment of 4 de-escalation zones in 2017 between rebel groups and those fighting on behalf of the Syrian government. M. Petkova, ‘What has Russia gained from five years of fighting in Syria?’, Al Jazeera, 1 October 2020; S. Abboud, ‘Syria’s war: What went wrong in east Aleppo?’, Al Jazeera, 8 December 2016; M. Petkova, ‘What has Russia gained from five years of fighting in Syria?’, Al Jazeera, 1 October 2020; ‘Syria’s ‘de-escalation zones’ explained’, Al Jazeera, 4 July 2017.

In September 2018, a demilitarized zone was created near the de-escalated zone of Idlib between Russia and Turkey. Although Russia began to withdraw forces at the end of 2017, they continued their airstrikes in support of the Syrian Regime up until 2023. In spite of a number of ceasefires concluded between Syria and rebel groups in Idlib, Russian airstrikes continued targeting the Idlib province. Furthermore, Russia carried out ground offenses in north-eastern and western part of Syria. International Crisis Group, Crisis Watch: Syria.

Russia and Turkey concluded another ceasefire in March 2020 in the Idlib province. The ceasefire lead to Turkey and Russia halting hostilities and conducting joint patrols through August 2020. Russia took up airstrikes again in the Idlib province in June 2020 and then expanded to strike parts of Latakia and Hama provinces and Aleppo governorate, striking opposition targets and artillery shelling through November 2022. International Crisis Group, Crisis Watch: Syria.

Wagner group

The Wagner Group has been present in Syria since at least the 2016 military operations around Palmyra. How “Wagner” came to Syria’, The Economist, 2 November 2017. On 7 February 2018, the United States and pro-Syrian government forces, including the Wagner Group, engaged in armed confrontations in Deir al-Zour province, whre Syrian forces made advances on the Conoco plant. The number of deaths is disputed, but ‘[t]he documents obtained by the Times estimated 200 to 300 of the “pro-regime force” were killed.’ T. Gibbons-Neff, ‘How a 4-Hour Battle Between Russian Mercenaries and U.S. Commandos Unfolded in Syria’, The New York Times, 24 May 2018. Russia has vaguely confirmed casualties of Russia citizens, while stating no Russian regular forces were present during the battle. Russia admits dozens of Russian casualties in Syria battle’, BBC, 20 February 2018. The reports from Syrian state media have reported dozens of casualties, however the total number is unknown. Syria conflict: ‘Russians killed’ in US air strikes’, BBC, 13 February 2018.

The Wagner Group has also been reported to have a role in fighting ISIS in Syria for nearly 10 years. Inside the Wagner Group, Russia’s mercenary force’, Al Jazeera, 18 November 2022; G. Waters, ‘ISIS beats back Wagner offensive in central Syria’, Middle East Institute, 21 April 2023. Notably, at the end of 2021 the Wagner Group was part of a large-scale military operation with other groups and regime forces against ISIS which covered the desert of Homs, parts of Aleppo province, and the deserts of Hama, Al-Raqqa and Deir Ezzor. Supported by Regime forces | Wagner and Fatemiyoun launch military campaign against ISIS in Syrian desert’, The Syrian Observatory For Human Rights, 22 December 2021. In 2022, the Wagner Group established a presence in the al-Kawm region, with a headquarters in the city of Palmyra with about 1.2000 Wagner personnel deployed. In late 2022, the Wagner Group took command over the military operations in al-Kawm and launced operations against ISIS going into 2023. In March 2023, the Wagner Group and the Syrian military were involved in a fight against ISIS over the village of al-Kawm in Badia which resulted in a stalemate. G. Waters, ‘ISIS beats back Wagner offensive in central Syria’, Middle East Institute, 21 April 2023.

All parties to the conflict are bound by Article 3 common to the 1949 Geneva Conventions that provides for the minimum standard to be respected and requires humane treatment without adverse distinction of all persons not or no longer taking active parts in hostilities. It prohibits murder, mutilation, torture, cruel, inhuman and degrading treatment, hostage taking and unfair trials. All parties are bound by customary international humanitarian law applicable to non-international armed conflict. Customary international law consists of unwritten rules that come from a general practice accepted as law. Based on an extensive study, the International Committee of the Red Cross maintains a database on customary international humanitarian law. In addition to international humanitarian law, international human rights law continues to apply during times of armed conflict. Under human rights law, the territorial state has an obligation to prevent and investigate alleged violations, including by non-state actors. Non-state armed groups are increasingly considered to be bound by international human rights law if they exercise de facto control over some areas.

State parties

Non-state armed groups

A wide array of non-state armed groups are active in Syria. Below is a selection of the most important armed groups or alliances:

  • The Islamic State group
  • The Syrian National Army (SNA), former Free Syrian Army (FSA)
  • Hay’at Tahrir al-Sham
  • Syrian Democratic Forces (including YPG)
  • Ahrar al-Sham
  • Hezbollah
Last updated: Thursday 10th August 2023