The rules of International Humanitarian Law define three fundamental principles governing the conduct of hostilities, that is, the fighting between parties to a conflict: distinction, proportionality, and precautions. These principles are customary in nature and must be respected at all times by all parties – states, non-state armed groups, and civilians directly participating in hostilities – in all armed conflicts, whether international or non-international. Certain categories of persons and property, such as units, means of transport and medical personnel, essential goods for the survival of the civilian population, and installations containing dangerous forces, benefit from additional stricter protection measures (see below the question of protecting civilian infrastructure).
The principles and rules governing the conduct of hostilities apply in all cases where combat takes place in the context of an armed conflict, whether on land (ground operations), in the air (air warfare), at sea (naval warfare), in the cyber realm (cyber operations), and in outer space.
The principles and rules of IHL governing the conduct of hostilities aim to protect the civilian population against the effects of hostilities, ensuring a balance between military necessity and humanitarian considerations through prohibitions and restrictions on the weapons, means, and methods of war that parties to a conflict may use.
The principle of distinction requires parties to always distinguish between civilians and combatants, as well as between military objectives and civilian objects, such as homes, civilian infrastructure, and the environment. Parties can only direct their attacks against combatants, never against civilians, and can only target military objectives, never civilian objects. Attacks without distinction, that is, attacks not directed at specific military objectives in accordance with the rules, which cannot be targeted in this way or whose effects cannot be contained as required by international humanitarian law, are also prohibited. Threats of violence aimed at spreading terror among the civilian population, as well as the use of famine as a method of war against the civilian population, are also forbidden.
Attacks directed against a combatant or other military objective must respect the principle of proportionality. This principle prohibits launching an attack that is expected to cause civilian casualties, injuries to civilians, or damage to civilian property that would be excessive in relation to the concrete and direct military advantage anticipated. In other words, any attack against a military objective must be preceded by an assessment to conclude that civilian losses and damages are not disproportionate to the expected military advantage.
The precautionary principle requires all parties to a conflict to constantly ensure the protection of the civilian population and civilian objects against the effects of military operations. Given the significant risk of harm to civilians in case of an attack, IHL imposes detailed obligations on those who plan, decide, or conduct attacks. It is especially important to take all practicable precautions to:
– Verify that the targets are military objectives; – Avoid and, in any case, minimize civilian casualties, injuries to civilians, and damage to civilian property; – Assess whether the attack is likely to violate the proportionality rule; – Cancel or suspend an attack if it appears to violate the principle of distinction or the rule of proportionality; – Give timely warning through effective means in case of attacks that may affect the civilian population.
IHL also requires parties to protect the civilian population and civilian objects under their authority against the effects of attacks. In cities, military and civilian persons and property are often closely intertwined. For parties to hostilities taking place in urban or other populated areas, this mingling presents significant challenges, both militarily and in avoiding harm to civilians. As urban warfare poses specific dangers to civilians, the protection provided by the principles and rules of IHL is crucial.
