Frequently Asked Questions: International Armed Conflict (IAC)

An International Armed Conflict is a situation where two or more states resort to armed force against each other. The key elements are:

• Parties to the conflict must be states (or groups acting on behalf of a state, or other entities with an international legal personality, such as international organizations).
• The use of force needs to be a hostile act and must not be the result of a mistake or an individual acting out of its own volition.

Even minor skirmishes between the armed forces – be they land, air or naval forces – may spark an IAC.

Once these conditions are met, International Humanitarian Law (IHL) applies, imposing rules on how the war must be conducted and protections for persons not or no longer participating hostilities (civilians, wounded, sick or shipwrecked combatants, prisoners, etc.).

In short, an IAC is any armed confrontation between the armed forces of two or more states, also referred to as High Contracting Parties. In such situations, IHL applies, bringing about humanitarian protections for those affected and obligations on parties to the conflict.

High Contracting Parties is the term used in the Geneva Conventions to refer to states party to the Conventions. States parties are bound to respect them. Since the Geneva Conventions have been universally ratified, all states are High Contracting Parties.

International humanitarian law distinguishes between "High Contracting Parties" and "parties to the conflict." High Contracting Parties refers to states that have ratified the Conventions, whether or not they are involved in an armed conflict. Parties to the conflict is the term used to refer to actors involved in an armed conflict. It may be used to refer to both states and non-state armed groups.

No. No formal declaration of war or recognition of the situation is required to trigger an IAC. The determination of whether an armed conflict exists depends on the prevailing circumstances on the ground, not the subjective views of the parties to the conflict. Rather than using the term "war," the Geneva Conventions use the term "armed conflict".

An IAC occurs when one or more States have recourse to armed force against another State, regardless of the reasons or the intensity of this confrontation. The existence of an IAC depends on what actually happens on the ground and is based on factual considerations. Only acts attributable to a State can trigger an IAC; acts of purely private persons do not constitute an IAC unless the private persons are acting on behalf of a State. 

IACs may take the form of an occupation and IHL of IACs will apply to cases of partial or total occupations, regardless of whether the occupation is met with armed resistance.

Contrary to non-international armed conflicts, which require that hostilities reach a certain threshold, there is no minimum threshold of armed violence for IACs. A single border skirmish between the armed forces of two States or the capture of an individual soldier may amount to an international armed conflict.

No. The determination whether an armed conflict exists within the meaning of Common Article 2 to the Geneva Conventions of 1949 depends on the prevailing circumstances, not the subjective views of the parties to the conflict. An IAC may arise between two or more High Contracting Parties even if the state of war is not recognized by one (or both) of them.

The classification of a situation as an armed conflict, and therefore the determination of the applicability of IHL, does not legitimize, legalize nor reprehend or prohibit the resort to force by any of the parties to a conflict under jus ad bellum.

Jus ad bellum refers to the conditions under which States may resort to war or to the use of armed force in general. The prohibition against the use of force amongst States and the exceptions to it (self-defence and UN authorization for the use of force) is set out in the United Nations Charter of 1945. 

Meanwhile, IHL, or jus in bello, applies as soon as a situation is considered an armed conflict. IHL applies to the belligerent parties irrespective of the reasons for the conflict or the justness of the causes for which they are fighting. That is why jus in bello must remain independent of jus ad bellum.

IHL does not regulate the question whether or under what circumstances an entity possesses statehood. It is irrelevant whether the other parties to the conflict recognize the statehood of the entity in question. Instead, the question whether a belligerent party possesses statehood is determined by other bodies of public international law.

The entirety of the four Geneva Conventions of 1949 apply to international armed conflicts. In addition, whenever ratified by the parties to an IAC, Additional Protocol I of 1977 applies to IACs and enhances the protection offered by the four Geneva Conventions. IACs are also governed by the Hague Regulations of 1907, relevant weapon-specific treaties (depending on ratification status) and customary IHL.

The declassification of conflicts must be based on the facts on the ground analyzed in light of the applicable IHL legal criterion. For the ICRC, this criterion is the general close of military operations. Hostilities must end with a degree of stability and permanence for the IAC to be considered terminated. A general close of military operations means not only the end of active hostilities, but also the end of military movements of a bellicose nature, including those that reform, reorganize or reconstitute, so that the likelihood of the resumption of hostilities can reasonably be discarded.

No. The termination of IAC is based on evidence on the ground and not on a ceasefire or peace agreement. Peace treaties do not always indicate the end or even the suspension of hostilities.

Yes. Human rights law continues to apply during armed conflict. However, all but the non-derogable provisions may be suspended, under certain conditions, in situations threatening the life of the nation. This means that in some exceptional circumstances and following certain procedures, states may suspend the applicability of certain human rights, for a limited period of time. IHL obligations may never be suspended as they were conceived to apply to situations of exception. States retain their human rights obligations in situations of armed conflict, including in occupied territories.

The classification of a situation of violence as an armed conflict does not legitimize the initial use of force.

The United Nations Charter governs the legality of resorting to the use of armed force (jus ad bellum), whereas the classification of an International Armed Conflict (IAC) falls under International Humanitarian Law and concerns the rules that apply once hostilities have begun (jus in bello). The Charter’s provisions determine whether the resort to armed force is legal under international law, but they do not affect, nor are they affected by, the IAC classification, which triggers the applicability of the law of armed conflict, also known as international humanitarian law. 

The ICRC is a neutral, impartial and independent humanitarian organization working to protect and assist those affected by armed conflict. It operates under a specific legal mandate derived from the 1949 Geneva Conventions, which have been universally ratified, and their Additional Protocols. This mandate is reinforced by the Statutes of the International Red Cross and Red Crescent Movement and customary international humanitarian law.

In IACs, states have specific obligations to allow the ICRC to visit prisoners of war and persons protected under GC IV, and to share information with the ICRC about certain categories of persons in their hands.

In all types of armed conflict, IACs and NIACs, the ICRC also has a broad right to offer humanitarian services. For instance, the ICRC may offer its services to visit persons deprived of their liberty in relation to the armed conflict, offer forensic expertise, facilitate family reunification, provide medical care and humanitarian assistance to individuals who do not or no longer participating in hostilities or act as a neutral intermediary between warring parties. The ICRC also has a duty to work for the faithful application of IHL.

Our adherence to the fundamental principles of neutrality, impartiality, and independence enables us to negotiate access to victims on all sides of a conflict and to address violations of humanitarian law through confidential bilateral dialogue, an approach that has proven effective in achieving tangible improvements while maintaining the trust necessary for continued humanitarian operations. While we have the legal right to offer our services, our humanitarian activities require the consent of relevant parties, which we strive to secure through our principled neutrality.

Two key conditions must be met for a situation of violence between a state and one or more organized armed groups or between such groups to be considered a NIAC: hostilities must reach a certain level of intensity and the groups involved must be sufficiently organized. Once these two thresholds are met, IHL applies, specifically Article 3 Common to the Geneva Conventions, where applicable, Additional Protocol II, and relevant customary norms. These rules impose minimum humanitarian standards, such as humane treatment of all persons not or no longer participating in the hostilities, prohibition of murder, torture, and taking hostages, and restrictions on the means and methods of warfare. 

If either one, or the two conditions are not met, the situation will not be regarded as a NIAC and IHL will not apply to that situation.

The legal classification of situations of violence (determining whether a situation of violence is an international armed conflict, a non-international armed conflict or neither) is key for understanding what rules of IHL, if any, apply to that specific context. The entirety of the four Geneva Conventions, as well as the rules of Additional Protocol I, when applicable, and relevant customary rules apply to international armed conflicts, while Common Article 3, Additional Protocol II, when applicable, and relevant customary rules apply to non-international armed conflicts.

There is no central authority under international law to classify a situation as an armed conflict. Parties to a conflict need to determine the legal framework applicable to the conduct of their military operations. The ICRC makes an independent determination of the facts and classifies situations. There are several reasons why the ICRC classifies conflicts. First, the High Contracting Parties to the 1949 Geneva Conventions have entrusted the ICRC, through the Statutes of the International Red Cross and Red Crescent Movement, “to work for the understanding and dissemination of knowledge of international humanitarian law applicable in armed conflicts and to prepare any development thereof”. Second, a fundamental part of the ICRC’s mandate is to support parties to comply with their legal obligations in situations of armed conflict. Thus, interpreting the notion of “armed conflict” with a view to determining the applicable legal framework is also important from an operational lens. Third, the existence of an armed conflict – whether international or non-international – is itself an important basis for the ICRC’s mandate. For example, in IACs, the ICRC has the right to visit prisoners of war and civilian internees. The Geneva Conventions also give the ICRC a broad right of initiative during NIACs. 

IACs occur between states, while non-international armed conflicts occur between states and organized armed conflicts or between organized armed groups. There are some important differences between the rules applicable to IACs and NIACs, including the combatant and PoW status, which only exist in IHL of IACs.

Yes. A situation can evolve from one type of armed conflict to another, depending on the facts prevailing at a certain moment. The classification depends on the prevailing circumstances on the ground.

The Geneva Conventions protect every individual or category of individuals not or no longer actively involved in hostilities:

• First Geneva Convention: Wounded or sick soldiers on land and members of the armed forces’ medical services
• Second Geneva Convention: Wounded, sick or shipwrecked military personnel at sea, and members of the naval forces’ medical services
• Third Geneva Convention: Prisoners of war
• Fourth Geneva Conventions: Civilians, such as:
  • foreign civilians on the territory of parties to the conflict, including refugees
  • civilians in occupied territories
  • civilian detainees and internees
  • medical and religious personnel or civil defence units.

Common Article 3 provides minimum protection in non-international armed conflicts. It is regarded as a treaty in miniature, representing a minimum standard from which belligerents should never depart. The rules contained in common Article 3 are considered to be customary law.

Additional Protocol I supplements the protection afforded by the four Geneva Conventions in international armed conflict. For example, it provides protection for wounded, sick and shipwrecked civilians and civilian medical personnel. It also contains rules on the obligation to search for missing persons and to provide humanitarian aid for the civilian population. Fundamental guarantees are provided for all persons, independently of their status. In addition, Additional Protocol I codified several rules on protection for the civilian population against the effects of hostilities.

IHL rests on a handful of core principles that guide the conduct of parties during armed conflict and protect those who are not, or are no longer, participating in hostilities.

IHL is a compromise between two underlying principles, of humanity and of military necessity. These two principles shape all its rules. The principle of military necessity permits only that degree and kind of force required to achieve the legitimate purpose of a conflict, i.e. the complete or partial submission of the enemy at the earliest possible moment with the minimum expenditure of life and resources. It does not, however, permit the taking of measures that would otherwise be prohibited under IHL. The principle of humanity forbids the infliction of all suffering, injury or destruction not necessary for achieving the legitimate purpose of a conflict. Persons not or no longer taking part in hostilities must be treated humanely, at all times.

Parties to a conflict must at all times distinguish between civilians and combatants in order to spare the civilian population and civilian property. Attacks may be made solely against military objectives. The principle of proportionality bars attacks whose expected incidental civilian harm would be excessive in relation to the concrete and direct military advantage anticipated. The principle of precaution requires parties to take all feasible measures to minimize civilian harm, such as verifying targets, issuing warnings, and selecting means of attack that reduce incidental harm.

These principles form the backbone of IHL, ensuring that even in war there are limits designed to preserve human dignity and protect vulnerable populations.

No. There is no reciprocity condition as far as respect of IHL is concerned. The fact that a party to a conflict has failed to respect the Geneva Conventions does not free the other party from its obligation to respect humanitarian law. One party cannot invoke the violation of a humanitarian rule by the other party to justify its own violations of IHL.

No. The Geneva Conventions clearly state that the application of IHL does not affect the legal status of parties to the conflict. This is particularly important in situations where one party may not officially recognize the other party or where the conflict involves non-State armed groups.

All three names refer to the same body of rules that try to limit the horrors of fighting. The law of war is the old, umbrella term that historically covered everything about war, including the question of whether a state may even start a war (the “right to use force”). Today, the law of armed conflict (LOAC) focuses in only on the conduct of hostilities once fighting has begun; it provides protections for civilians, wounded and sick soldiers, prisoners of war, the dead, and limits on what weapons Parties may (or may not) use and how, without judging whether the war itself is legal. International humanitarian law (IHL) is the same rule set as LOAC, but the name highlights its humanitarian purpose: protecting people from unnecessary suffering and ensuring aid can reach those in need. The ICRC uses the term IHL.

The core IHL obligations are drawn from the four Geneva Conventions of 1949 (and their Additional Protocols), which set the baseline standards for the humane treatment of victims of armed conflict. In short, “law of war” is the broad, historic term; LOAC and IHL are the modern, more precise terms that concentrate on the conduct of hostilities and the protection of people, with the Geneva Conventions and Additional Protocols serving as the foundational legal source.