This article is part of the World Economic Forum's Geostrategy platform

Military operations are taking place with increasing frequency in densely populated areas.

Such operations result in loss of life and harm to civilians, as well as damage to civilian objects, (including infrastructure providing essential services).

In order to protect civilians, it is imperative that armed forces and groups comply with the rules of international humanitarian law on the conduct of hostilities, including the rule of proportionality.

The rule of proportionality prohibits attacks 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.

Proportionality in the Conduct of Hostilities:The Incidental Harm Side of the Assessment analyses the key steps that belligerents must take to give effect to the rule, with a particular focus on one side of proportionality assessments – the expected incidental harm.

Those undertaking proportionality assessments before or during an attack must consider whether the expected harm will be caused by the attack, and whether that harm could be expected (that is, was it reasonably foreseeable).

For the purpose of proportionality assessments, injury to civilians includes disease, and there is no reason in principle to exclude mental harm, even though it is currently challenging to identify and quantify it. Damage to civilian objects includes damage to elements of the natural environment.

Determining harm

Once the incidental harm to be considered has been identified, a value or weight must be assigned to it. This is then balanced against the value or weight of the military advantage anticipated from the attack to determine whether the harm would be excessive.

In the determination of whether the expected incidental harm would be excessive compared to the anticipated military advantage, ‘excessive’ is a wide but not indeterminate standard.

Belligerents should develop methodologies so that those planning and deciding attacks are provided with all necessary information on expected incidental harm, and to assist them in assigning weight to the incidental harm to be considered.

If it becomes apparent that the rule of proportionality will be contravened, the attack in question must be cancelled or suspended.

Proportionality and compliance

Clarification of the law is important in ensuring compliance with the rule of proportionality, but a culture of compliance within armed forces and groups, inculcated by their leaders, is also crucial.

The report reaches a number of conclusions and recommendations

1) Belligerents must take the necessary measures to ensure compliance with the rule of proportionality by members of their forces at all levels and in all circumstances.

These measures can include:

  • incorporating the rule and the measures necessary to give it effect in military manuals, doctrine and rules of engagement;
  • establishing systems to gather and analyse relevant information and to ensure that this information is taken into account in the targeting cycle;
  • establishing and institutionalizing procedures to ensure proportionality considerations are taken into account throughout the targeting cycle;
  • conducting ‘lessons learned’ processes as soon as possible after attacks, to inform future attacks;
  • conducting an assessment of attacks when the rule may have been violated;
  • addressing the rule in training materials and scenario-based exercises;
  • making legal advisers available to advise military commanders at the appropriate level.

2) The rule of proportionality is binding on parties to an armed conflict and must be complied with by all their organs and those acting on their behalf.

Every attack decision must comply with the rule: during deliberate targeting, dynamic targeting and combat engagement.

What will differ with context, and the seniority of decision-makers, is what can be considered reasonable in terms of (a) the collection and analysis of information on expected incidental harm and anticipated military advantage, and (b) the sophistication of the proportionality assessments.

3) All members of belligerents’ forces who are in a position to determine, even once an attack has been launched but at a time when it can still be cancelled or suspended, that it is apparent that the attack would violate the rule of proportionality must cancel or suspend it.

4) In addition, those executing an attack who become aware of facts that they believe could affect the proportionality assessment must report this to those coordinating the operation, so that the new information can be taken into account. Systems should be put in place to ensure that it is possible for all those conducting or involved in attacks to provide such information.

5) Belligerents should have a system in place to effectively gather and analyse information on incidental harm. This should include information in the public domain, information that can be acquired by the belligerents’ intelligence-gathering systems, and information based on past practice.

Recognizing that belligerents have different capabilities and resources, the units responsible for planning attacks must do everything feasible to have access to information and analysis on a range of factors that can affect incidental harm, and must make use of this information in their assessments.

6) Belligerents should include incidental harm in battle damage assessment methodologies, recognizing that there may be circumstances in which it might not be feasible to collect this information.

After-action reviews should be conducted as soon as possible after attacks, so that their conclusions can inform the targeting cycle in the course of an operation. Incidental harm should also be addressed in broader ‘lessons learned’ exercises, including information on the harm caused in past attacks, in order to further refine proportionality assessment methodologies.