Non-international armed conflicts

Non-international armed conflicts (NIAC) involve either a State fighting one or more allied organized armed group(s), or at least two organized armed groups fighting each other. For a NIAC to exist, two criteria must be met under Article 3 common to the four 1949 Geneva Conventions and customary international law:

Intensity of armed violence: must be ‘protracted’ – meaning that the violence must have reached a certain level of intensity.
Degree of organization: the armed groups must exhibit a certain degree of organization. State armed forces are presumed to be organized.

The criteria, which are assessed on a case-by-case basis, are used for the purpose of distinguishing an armed conflict from internal disturbances and tensions (such as riots), and isolated and sporadic acts of violence (including terrorist acts). According to international case-law, certain indicative factors can be used to assess them, including:

For intensity: the number, duration and intensity of individual confrontations; the types of weapons and military equipment used; the material destruction and casualties; the number of refugees and internally displaced persons; the reaction of the government (including the use of force and the application of a legal framework); the reaction and involvement of the international community. In a coalition of armed groups that maintain a sufficient degree of coordination, aggregated violence by its members against the enemy may meet the criterion of intensity.¹

For organization: the presence of some kind of command structure; the ability to define a unified military strategy and use military tactics; the ability to plan, coordinate and carry out military operations; the exercise of some kind of territorial control; the capacity to access to weapons and other military equipment; the ability to recruit and train members; the ability to negotiate and conclude ceasefire agreements and peace accords; and the existence of internal discipline mechanism.²

A NIAC ends when either the intensity or organization criterion is no longer met. With respect to intensity, it must be clear that the lack of hostilities is not merely a lull in the fighting but a sustained end to the hostilities. There is, however, no requirement, as indicated by a 1995 decision of the ICTY in the Tadić case,³ for a peace treaty to be concluded.

In NIACs, Additional Protocol II of 1977 sets out additional rules, including on the conduct of hostilities (which are not governed by Common Article 3 of the Geneva Conventions of 1949). Most – if not all – of the Protocol’s rules are reflected in customary IHL. For the Protocol to apply, the conflict must occur in the territory of a State party to Additional Protocol II of 1977, and it must take place between governmental armed forces and an organized armed group. The armed group must exercise a degree of territorial control that enables them to carry out sustained and concerted military operations and to implement the Protocol.⁴ Once the Protocol does apply, it also applies to any foreign State (Party) that assists the territorial State in its fight against the armed group.⁵

The support-based approach to classifying armed conflicts means that other States or international organizations that provide military support to a State that is party to a pre-existing NIAC themselves become parties to the NIAC. The same applies to armed groups that support either the State or the non-State armed group that is party to the NIAC. In each case, the ‘decisive element is the third party’s direct and effective contribution to the collective conduct of hostilities by the support it provides’ to the party to the pre-existing NIAC.⁶

1
‘How is the Term “Armed Conflict” Defined in International Humanitarian Law’, ICRC, Geneva 2024, p 17; J. Nikolic et al, ‘Aggregated intensity: classifying coalitions of non-State armed groups’, ICRC, Geneva, 7 October 2020; S. D’Cunha et al, ‘Defining armed conflict: some clarity in the fog of war’, ICRC, Geneva, 2 May 2024.
2
See eg ICTY, Prosecutor v Haradinaj, Judgment (Trial Chamber) (Case No IT-04-84-T), 3 April 2008, paras 49 and 60.
3
ICTY, Prosecutor v Tadić, Decision on the Defence Motion for Interlocutory Appeal on Jurisdiction (Appeals Chamber) (Case No IT-94-1-AR72), 2 October 1995, para 70.
4
Art 1(1), Additional Protocol II of 1977.
5
This is because the Protocol explicitly applies to ‘all armed conflicts’ which take place in the territory of a State Party between its armed forces and dissident armed forces or other organized armed groups and not merely to those two parties.
6
‘How is the Term “Armed Conflict” Defined in International Humanitarian Law’, ICRC, Geneva, 2024, p 16.