International Armed Conflict (IAC)

Unique identifier / Notation

SO0101

Synonyms

Interstate armed conflict State-based armed conflict IAC

International armed conflict covers all cases of declared war and other de facto armed conflict between two or more States, even if the state of war is not recognised by one of them and/or the use of armed force is unilateral (ICRC, 2024).

Primary reference(s)

ICRC, 2024. Opinion Paper, “How is the term ‘armed conflict’ defined in IHL?”. Accessed 31 May 2025.

Annotations

Additional scientific description

Common Article 2 of the Geneva Conventions of 1949 defined International Armed Conflict (IAC) as, "all cases of declared war or of any other armed conflict which may arise between two or more of the High Contracting Parties, even if the state of war is not recognized by one of them." IAC "exists whenever there is a resort to armed force between States" (ICTY, 1995) and "can always be assumed when parts of the armed forces of two States clash with each other" (Schindler, 1979). The Geneva Conventions refer to States that are party to the Conventions as 'High Contracting Parties'.

International armed conflict is conceptually broader and more flexible than the notion of war between States because IAC is based on objective and factual criteria and does not rely on the formal declaration of war (ICRC, 2016). By extension, the termination of IAC is based on evidence on the ground and not a ceasefire or peace agreement (ICRC, 2016). Article 6(2) of the Fourth Convention stipulates that the Convention ceases to apply when there is objective evidence of "the general close of military operations" and the International Criminal Tribunal for the former Yugoslavia (ICTY) ruled that International Humanitarian Law "extends beyond the cessation of hostilities until a general conclusion of peace is reached" (ICTY, 1995: para. 70).

The category of IAC encompasses a broad range of armed confrontations between two or more States including, but not limited to:

"All cases of partial or total occupation of the territory of a High Contracting Party, even if the said occupation meets with no armed resistance" (ICRC, 1949, Article 2[2]).
"An unconsented-to invasion or deployment of a State's armed forces on the territory of another State - even if it does not meet with armed resistance" (ICRC, 2016, para. 223).
The use of armed force not directed against the enemy's armed forces but only against the enemy's territory, its civilian population and/or civilian objects, including (but not limited to) infrastructure (ICRC, 2016, para. 224)
"Armed conflicts in which peoples are fighting against colonial domination, alien occupation or racist regimes" (ICRC, 1977, Additional Protocol I, Article 1[4], para. 1).
"Minor skirmishes between the armed forces, be they land, air or naval forces" Any unconsented-to military operations by one State in the territory of another State (ICRC, 2016, para. 237).
When a situation objectively shows for example that a State is effectively involved in military operations or any other hostile actions against another State, neutralizing enemy military personnel or assets, hampering its military operations or using/controlling its territory (ICRC, 2016 para. 241)
Cyber operations having similar effects to classic kinetic operations (ICRC, 2016, para. 255)
State's overall control over non-State armed groups fighting another State (ICRC, 2016, para. 265 and sq.)

Metrics and numeric limits

The identification and classification of IAC is not conducted by a central authority, and there is no minimum threshold of intensity or duration for a confrontation to be considered a situation of IAC (ICRC, 2016).

Academic conflict datasets are available; they provide their own operational thresholds for the minimum number of annual fatalities for NIAC events and trends to be included. For example, two of the most influential academic conflict datasets, the Uppsala Conflict Data Program (Uppsala Universitet, no date) and the Correlates of War (The Correlates of War Project, no date) apply annual conflict-related fatality thresholds of 25 and 1000, respectively. The Correlates of War seeks to facilitate the collection, dissemination, and use of accurate and reliable quantitative data in international relations. Key principles of the project include a commitment to standard scientific principles of replication, data reliability, documentation, review, and the transparency of data collection procedures.

Key relevant UN convention / multilateral treaty

Article 2 Common to the Geneva Conventions. Geneva Convention Relative to the Protection of Civilian Persons in Time of War (Fourth Geneva Convention) (ICRC, 1949).

Protocol additional to the Geneva Conventions of 12 August 1949 and relating to the Protection of Victims of International Armed Conflicts (Protocol I) (ICRC, 1977).

Drivers

The Global Platform underscored the security implications of climate change and disasters and encouraged more context-specific disaster risk reduction and resilience-building strategies in conflict-affected countries and fragile contexts based on risk assessments that integrate disaster, climate risks and conflicts (UNDRR, 2019).

Impacts

Armed conflict carries immediate and severe impacts on human lives, health, and dignity with increasing numbers of military personnel and civilians being killed, wounded, treated without dignity, arbitrarily detained and/or separated from their families. They may have been targeted on purpose, forced to leave their homes, and deprived of their basic rights as human beings, such as the right to supplies essential to their survival” (ICRC, 2023).

Impacts could include impacts from the use of biological agents (BI0602), chemical agents (CH0903), nuclear agents (TL0603) and explosive agents (TL0306). Additionally, explosive ordnance (explosives remnants of war) (SO0201) and environmental degradation from conflict (SO0202) may have impacts.

Multi-hazard context

Since the 1970s, an emerging body of work has sought to deepen and nuance understanding of the construction of disaster risk, and the intersection of natural hazards with violence, conflict and fragility. The interplay between disasters, climate change, environmental degradation, and fragility should be recognized, including in the context of water-related risk (Peters, 2019).

The dynamic nature of systemic risks, new structures to govern risk in complex, adaptive systems and develop new tools for risk-informed decision-making that allow human societies to live in and with uncertainty. This is particularly needed where environmental, health and financial systems, supply chains, information and communication systems are clearly vulnerable. These are challenged by, and are causal drivers of, disruptive influences such as climate change, loss of biodiversity and ecological systems degradation, disease outbreaks, food shortages, social unrest, political instability and conflict, financial instability and inequality. They also create vulnerability on multiple spatial scales (local to global) and across different timescales (from immediate to decadal and beyond) (UNDRR, 2019).

Disasters can also impact people who have already been forcibly displaced by conflict or other reasons (UNDRR, 2025).

Risk Management

Everyone has the right to protection against hazards, regardless of whether they live in a relatively peaceful and stable society, or one where challenges associated with violence, conflict and fragility are rife. Where these challenges exist, vulnerabilities are highest and capacities to manage disaster risk are often insufficient. For these reasons, conflict contexts require dedicated support for disaster risk reduction (Peters, 2019).

Disaster risk reduction naturally takes preventive action seriously, advocating for more investment in preparedness and mitigation. This position has transformed the agenda from better managing disasters to reducing disaster risk. Flexibility, the ability to work within complexity and the nimbleness to respond and incorporate large-scale shifts in global agendas are required now more than ever. In this spirit, greater collaboration is required between disaster risk reduction and peacebuilding and conflict prevention communities. The disaster risk reduction community should not be seen as a separate actor; rather disaster risk reduction should be integrated into the platforms and processes that exist in fragile and crisis settings (Peters, 2019).

International humanitarian law (IHL) is a set of rules which seek, for humanitarian reasons, to limit the effects of armed conflict. It protects persons who are not or are no longer participating in the hostilities and restricts the means and methods of warfare. International humanitarian law is also known as the law of war or the law of armed conflict. International humanitarian law is part of international law, which is the body of rules governing relations between States. International law is contained in agreements between States – treaties or conventions –, in customary rules, which consist of State practice considered by them as legally binding, and in general principles. International humanitarian law applies to armed conflicts. It does not regulate whether a State may actually use force; this is governed by an important, but distinct, part of international law set out in the United Nations Charter (ICRC, 2004).

Monitoring

Monitoring armed conflicts involves observing, tracking, and analyzing various aspects of conflict situations to understand their dynamics, impact, and potential for escalation or de-escalation. This can be done through various methods, including satellite imagery, field reports, and online portals, with the goal of informing decision-makers and promoting peace efforts.

Various mechanisms exist including the Geneva Academy Rule of Law in Armed Conflict Online Portal (RULAC) which classifies all situations of armed violence that amount to an armed conflict under international humanitarian law. Currently, it monitors more than 110 armed conflicts and provides information about parties, the latest developments, and applicable international law. Some of these conflicts make the headlines, others do not. Some of them started recently, while others have lasted for more than 50 years (Geneva Academy, no date).