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Non-international armed conflicts: Challenges for classification and the case of Syria

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1. Defining non-international armed conflicts within the framework of IHL

International Humanitarian Law (IHL) seeks to contain the effects of an armed conflict by limiting the methods and means of warfare and by protecting people who are not, or no longer, taking part in the hostilities. Categorizing an armed conflict properly is crucial to establish the rules that will apply during the conflict. While an international armed conflict (IAC) involves two or more States, a non-international armed conflict (NIAC) refers to a situation of violence involving sustained armed confrontations between government forces and one or more organized armed groups or between such groups themselves, arising on the territory of a State[1]. Historically, NIACs were considered an internal matter of the concerned States, to which no international law provisions applied. This view strongly changed following the adoption of Common Article 3 to the four Geneva Conventions in 1949, where States agreed to determine minimal guarantees to be respected during armed conflicts that do not have an international character.

The notion of non-international armed conflict was reaffirmed and dealt with accordingly in Article 1 of Additional Protocol II, which complements Common Article 3 by introducing the requirement of territorial control. It provides that dissident armed forces or other organized armed groups “exercise such control over a part of its territory as to enable them to carry out sustained and concerted military operations and to implement this Protocol”.

International tribunals have also contributed to the customary evolution of IHL rules applicable to NIACs. Today it is broadly accepted that the more detailed rules of international conflicts can serve as a framework for interpreting of the general principles of NIACs or be applied to them by analogy. Hence, the applicable rules to non-international armed conflict are also contained in customary international humanitarian law.

Two criteria must be met to classify a situation as a non-international armed conflict:

  • The armed groups involved must show a minimum degree of organization, so they should possess a chain of command structure (transmit and enforce orders, plan and launch coordinated large-scale military operations, capacity to recruit, train, and equip new fighters, and control part of the national territory).

  • The armed conflict must reach a minimum level of intensity, determined by indicators such as the duration and the gravity of the fighting, the forces and troops involved, the weapons used, the number of casualties, and the damage caused.

It should be recalled that NIACs are different from other forms of collective violence. As stated in Article 1(2) of Additional Protocol II, IHL “[…] not apply to situations of internal disturbances and tensions, such as riots, isolated and sporadic acts of violence and other acts of a similar nature, as not being armed conflicts”. However, non-applicability does not mean lesser protection for the people.

The fact that a non-State group is part of an armed conflict does not give it any status under IHL. It does, however, create significant legal obligations to any party involved in the fighting, such as the guaranteeing of human treatment without discrimination to persons wounded during the hostilities. Worth to remember that the application of IHL does not affect the sovereignty of a State or a government’s right to suppress rebellion through armed force and to prosecute insurgents under its own laws. IHL only regulates how the fighting takes place, not why.

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2. Contemporary challenges for classification

The classification of armed conflicts has always been a complex topic for lawyers and legal advisers. When categorizing contemporary armed conflicts, some factors should be considered as they can pose challenges to the traditional classification. In fact, there are situations in which both IAC and NIAC coexist, or this coexistence develops during the evolution of a conflict or, again, different non-State actors that fight against each other.

In the case of military intervention by a foreign State in support of another State, therefore the latter is not a target and agrees to the intervention, the conflict will remain of a non-international character. The question is less clear when a State intervenes in another State’s territory without consent and conducts its military action only against non-State actors located in the territorial State, usually as a response to armed group actions perpetrated from the territorial State, not uncommon to see in contemporary times.

When classifying armed conflicts, two leading schools of thought seem to be more followed[2]. One view is that any use of force on another State’s territory without consent will constitute an IAC. The other, more widely supported, is that an intervention that does not target the State’s organs or assets, directed exclusively against a non-State group, is considered a NIAC (if the intensity and organizational criteria are satisfied), notwithstanding the lack of consent by the territorial State. This matter is not yet definitively settled under international law. For sure, an intervention may impact a State’s population or its national resources; however, if these are located where the armed group operates, they probably will not be any more under the territorial State’s control, thus they can no longer be identified with that State for any purpose related to the legal obligations on the conduct of hostilities. Different is the situation in which the intervening State occupies the territory. In this case, we would start talking about IACs[3]. Hence, in the absence of a clear occupation, it is difficult to assume that attacks directed against an organized armed group operating within a State can be considered an attack on that State. If the intervening and territorial States are engaged in hostilities with each other or if the armed forces imprison members of the other State, only this case would trigger the applicability of the IAC system. Thus, it depends on the ad hoc situation not on the simple violation of sovereignty. Many examples support this thesis, such as the actions taken by the Kenyan armed forces in Somalia to fight Al-Shabaab. In none of these, the States concerned consider themselves involved in an armed conflict with each other. This is also the case of the United States’ intervention anti-ISIS in Syria.

A third position could be added, certainly a minority one, which supports the idea that the classification is primarily based on the nature of the parties (involvement of at least one non-State actor) and not on the consent by the territorial State.

The case differs when a State supports armed groups acting on another State’s territory. What can look like a NIAC between the territorial State and the armed group amounts to an IAC between the territorial State and the country supporting the non-State actors if it exercises overall control over the group (organize, coordinate, or finance the operations).

It can be concluded that, in order to be able to categorize the different types of hostilities, the following factors should be taken into account:

  • the nature of the parties involved in hostilities (States or non-State);

  • how the intervention is conducted (against the State or non-State group);

  • if the intervening State occupies part of the territory;

  • whether people are deprived of their freedom;

  • the control of territory, population, and infrastructure of the territorial State;

  • the relationship between the targeted armed group and the territorial State;

Today, under customary international law, the differences between the two categories of conflict are slowly disappearing. After ten years of research and study, the International Committee of the Red Cross (ICRC) concluded that 141 out of 161 rules of customary humanitarian law apply to international armed conflicts as well as to non-international armed conflicts. The nature of contemporary armed conflicts is gradually changing, and the binary distinction between IAC and NIAC will continue to be questioned.

3. A possible third category: internationalized conflicts

Pic.3 Source: UN Peacekeeping

Another element that hampers the categorization of armed conflict is the so-called “peacekeeping operations” led by a regional organization such as the Africa or European Union or by the United Nations (UN). Some argue that these internationalized conflicts constitute a third category of conflicts and could be labeled as “transnational” or “extraterritorial”. However, to date, under IHL every armed conflict must be classified using the binary distinction of international or non-international.

The main concerns relating to classification arose when it comes to operations in which the forces operating under the auspices of a regional organization or the UN support a territorial host government involved in a NIAC to the point they become a party to the conflict; however, we are still talking about a NIAC between States on one side and the organized armed groups on the other side. In the rare cases in which peacekeeping forces are involved in hostilities against a host State, it will become an international armed conflict. This would raise additional concerns about whether there can be an IAC between an international organization and a State. In cases of forces operating under the auspices of organizations such as NATO, Member States provide troops to be at the disposal of these organizations. However, they retain some authority over their forces. In addition, multinational forces may be involved in different degrees; thus, not every involved State can be considered part of the conflict. Also, in many instances, multinational forces are not directly involved in combat but only provide support to the territorial State engaged in an existing NIAC.

4. Classification of the ongoing armed conflict in Syria

Currently, multiple and overlapping conflicts of non-international character are taking place in the Syrian Arab Republic (SAR) territory. The Syrian Government, helped by its allies, is involved in various NIACs against different rebel groups. At the same time, these armed groups are engaged in parallel internal NIACs between each other and with foreign State forces.

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Assessing the degree of involvement and the relationship between the various actors involved in the armed conflicts currently undergoing in Syria would help classify the nature of these conflicts. Together with its associated forces, the Syrian government is involved in a NIAC with the National Coalition of Syrian Revolution and Opposition Forces, commonly named Syrian National Coalition. Even if the coalition’s opposition group have sometimes clashed, they cooperate to achieve the shared goal of overthrowing the current Syrian government led by Bashar al-Assad.

A separate part of this NIAC is made up of a variety of jihadist groups allegedly associated with Al-Qaeda, of which the most notable to date has been Hay’at Tahrir al-Sham (HTS), the successor of Jabhat al-Nusra. While sharing the opposition’s goal of overthrowing the Syrian government, they possess their own agenda. Thanks to the organizational level reached, the group was able to obtain control of a significant portion of the Syrian territory, so much so that it was considered a part of the non-international armed conflict.

The same is true for the Islamic State of Iraq and Syria (ISIS), active in the SAR since 2013. Intending to establish an Islamist caliphate, this group opposes the Syrian government, the principal opposition, the Kurdish armed groups, and the ideological aligned jihadists of HTS. As it controlled a significant part of the territory and population within Syria, it can also be considered a party of the NIAC. Another NIAC can be identified in the northern part of the SAR, between the Turkish forces and the pro-Kurdish organizations. The clashes between Turkish forces and Syrian Kurdish militias along the border have significantly increased in number and intensity since February 2016, evidence that the threshold has been crossed.

Finally, an international anti-ISIS coalition led by the United States began aerial operations in Syria against Daesh’s held positions in September 2014 and, since then, more than 9000 airstrikes have been conducted. In addition, the United States conducts operations against the Khorasan group, an Al-Qaeda affiliate group also engaged in a NIAC with the Syrian government.

The intervention of Russia and Iran, as well as Hezbollah and Shia militias on the side of the SAR, does not affect the classification of the conflict, nor it amounts to another conflict, as they are in direct support of the government. There is no evidence that the allies act in the name of their home States or exercise control, more than a simple influence, over the Syrian government. Similar considerations can be made to States providing support to the rebel forces, such as Türkiye, which offered refuge on its territory to the Free Syrian Army leadership and ensured relative freedom of movement for opposition fighters. At the same time, a couple of Arab Gulf countries such as Saudi Arabia and Qatar, contribute to rebel groups’ arms procurement in the same way as the European Union and the United States offer technical assistance; however, as there is no evidence that these States are controlling the groups, the conflict remains of non-international character.

5. Conclusion

There is still no consensus, under the IHL perspective, on how to assess contemporary NIACs and how they relate to each other. Classifying armed conflicts is far from an easy task, and NIACs are even more controversial. As analyzed above, two main visions concerning governments’ consent to foreign military intervention influence the classification. However, the consent (or lack of consent) by a State should not be seen as a determinant factor for a conflict to become international. Debates will continue about the role that consent should play and how other factors may influence the categorization of the nature of armed conflict. Likewise, other questions relating to the consequences of classification remain subject to debate.

Classification is often easier when the conflict is over. For that reason, it would be simpler if the rules for both types of conflicts were identical.

The various armed hostilities within the Syrian Arab Republic’s borders have developed from a popular uprising started at the beginning of 2011 to a complex set of conflicts involving several parties that include both State and non-State actors. The difficulties encountered giving a legal classification to the Syrian armed conflict, raise concerns about the validity of the traditional division between IACs and NIACs.

Nowadays, there are many ongoing discussions about whether the current IHL dichotomy is sufficient to deal with the new scenarios or if new classifications are needed. With the new types of wars, significantly different from those of which the law of armed conflicts was firstly developed, arises the need to adapt IHL to the challenges posed by contemporary times. By renegotiating certain norms of IHL and filling the existing legislative gaps, it would be possible to guarantee greater law applicability to modern conflicts.

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[1] There is no real difference between NIAC and civil war. Common Article 3 does not use the term civil war, instead refers to “Conflicts not of an international character”. [2] For furter information visit: [3] A territory is considered as occupied when it is actually placed under the authority of the hostile army.


  • D. E. GRAHAM, Defining Non-International Armed Conflict: A Historically Difficult Task. International Law Studies, Vol.88, p. 43-55.

  • T. D. GILL, Classifying the Conflict in Syria. International Law Studies (Naval War College), 92, 353-380.

  • F. ANGELI, The Distinction between International and Non-International Armed Conflicts: Challenges for IHL?, 2015.



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