What Is the Principle of Proportionality in International Humanitarian Law?

The principle of proportionality is one of the fundamental principles of international humanitarian law (IHL). It applies to the planning and conduct of military operations and is intended to limit harm to civilians and civilian objects resulting from attacks on lawful military objectives.

This principle is sometimes mistakenly understood as requiring parties to an armed conflict to respond to one another using the same means or to the same extent. In reality, the principle of proportionality in IHL has nothing to do with the symmetry of military action. Instead, it requires an assessment of whether the foreseeable incidental harm to civilians and civilian objects would be excessive in relation to the concrete and direct military advantage anticipated from an attack.

When planning an attack, those responsible must assess the expected incidental harm, including possible civilian casualties and damage to civilian objects that may result from an attack on a lawful military objective.

Article 51(5)(b) of Additional Protocol I to the 1949 Geneva Conventions prohibits the following:

“an attack which may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, which would be excessive in relation to the concrete and direct military advantage anticipated.”

The principle of proportionality should not be confused with the principle of distinction. The principle of distinction requires parties to an armed conflict to distinguish at all times between civilians and combatants, and between civilian objects and military objectives. By contrast, the principle of proportionality applies when assessing the expected incidental harm to civilians and civilian objects resulting from an attack directed against a lawful military objective.

Respect for these principles is essential to limiting the humanitarian consequences of armed conflict and protecting civilians.

The Ukrainian Red Cross continues to promote knowledge of the rules and principles of international humanitarian law through information and awareness-raising activities.