This piece is cross-posted at EJIL: Talk!

In December 2018, the International Law Program at Chatham House published a report, “Proportionality in the Conduct of Hostilities: The Incidental Harm Side of the Assessment,” analyzing the key steps in making assessments about proportionality under international humanitarian law, with a particular focus on expected incidental harm to civilians and civilian objects.

Chatham House prepared the report following a series of expert consultations, including participation from military and government lawyers, representatives of humanitarian organizations, and academics. It also draws from review of IHL treaty texts, case law, and, to the extent practicable, military doctrine.

The report addresses three sets of questions about the rule of proportionality: First, the report examines what it means for the harm to be caused by the attack and the concept of foreseeability of harm, the weight to be assigned to particular kinds of harm, and how to assess whether the expected incidental harm to civilians and civilian objects is excessive in relation to the anticipated military advantage. Second, it analyses types of incidental harm to be considered in proportionality assessments. Third, it explores vexing legal issues that arise in implementation of the rule in practice (such as the type of information commanders should assess in “after attack” battle damage assessments).

In collaboration with Chatham House, EJIL:Talk! and Just Security have invited leading international humanitarian law experts to contribute to a joint online symposium on key issues addressed in the report. This week, we will host the following series:

(1) Emanuela Gillard, Chatham House Report on Proportionality in the Conduct of Hostilities – Some Key Elements (EJIL: Talk! and Just Security)

(2) Adil Haque, Proportionality and Doubt (Just Security)

(3) Lawrence Hill-Cawthorne, The Chatham House Paper on Proportionality in the Conduct of Hostilities (EJIL: Talk!)

(4) Geoffrey Corn, Calibrating the Compass of Proportionality (Just Security)


IMAGE: Palestinians inspect destroyed buildings in part of Gaza City’s al-Tufah neighbourhood on August 6, 2014. (Photo by MAHMUD HAMS/AFP/Getty Images)