Civilian Casualties in Modern Warfare: The Death of the Collateral Damage Rule

52 Pages Posted: 20 Sep 2011 Last revised: 9 Jun 2012

See all articles by Valerie Epps

Valerie Epps

Suffolk University Law School

Date Written: September 16, 2011


Members of armed forces are sent off to war to kill enemy combatants. They are not sent off to kill civilians. Nonetheless, modern wars invariably result in far more civilian deaths than military deaths. This article examines the collateral damage rule, one of the central operational rules regulating the conduct of hostilities, that essentially only permits civilian casualties when they are incidental to an attack on a legitimate military target. The rule is explored in light of the changing nature of warfare over the last two centuries including the shifting ratios of military to civilian war-related deaths. The article ultimately questions the continuing validity of this rule when, in recent decades, the overall statistics for war-related deaths reveal that civilian fatalities are considerably greater then military deaths.

The collateral damage rule is meant to offer protection to civilians in war time and to give content to the principle of distinction in contexts where military and civilian targets are interwoven. That statement reflects the usual assessment of the collateral damage rule but this article asks whether that assessment simply tricks us into thinking that ethical military advisors, by following the rule, will, in fact, avoid all but incidental damage to civilians. If the many and varied studies on the ratios of civilian to military war-related deaths reveal disproportionate civilian deaths (as they do) and if the many and varied epidemiological studies reveal war-related civilian displacement, disease, deprivation, and famine (which they do), the article asks whether the collateral damage rule has become simply an organized deceit to persuade us that when we condone the combatant’s privilege (soldiers being permitted to kill enemy soldiers) we are not signing the death warrant for civilians, except “incidentally.” The article will argue that in the context of modern warfare, the collateral damage rule can never accomplish what it purports to do, except in the most temporarily restricted sense. It will then explore what should be the fate of a legal rule, in this case at the heart of the laws of armed conflict, that cannot, by the nature of the context in which the rule is operative, be effective.

Trying to determine when there is sufficient armed violence to constitute armed conflict or war is difficult and varies depending on what is being studied. Classifying the different types of armed conflict is controversial and changes depending on the focus of research. Quantifying military and civilian deaths in armed conflict presents multiple classification problems and much disputed or unavailable data. Nonetheless, despite all of these difficulties, it is possible to discern significant trends within the last two centuries. This article will first examine the changes that have taken place, over roughly the last two centuries, in the types of wars that occur. It will next focus on the shifting ratio of military to civilian war-related deaths during this period, noting that we now live in an era where wars result in a hugely disproportionate loss of civilian lives. The final part of the article will trace the history and applicability of the collateral damage rule, also known as the proportionality rule. The article then brings together the data on the changes in the types of wars fought and the shift from mainly military to mainly civilian war-related deaths and asks what continuing regulatory effect the collateral damage rule can be expected to exert when the data on war-related deaths will inevitably mean that the rule has utterly failed to achieve its purpose. The final part of the article makes a few modest suggestions that may, in some measure, help fulfill the purpose of the collateral damage rule.

Suggested Citation

Epps, Valerie, Civilian Casualties in Modern Warfare: The Death of the Collateral Damage Rule (September 16, 2011). Georgia Journal of International and Comparative Law, Vol. 41, Winter, 2013, Suffolk University Law School Research Paper No. 11-39, Available at SSRN: or

Valerie Epps (Contact Author)

Suffolk University Law School ( email )

120 Tremont Street
Boston, MA 02108-4977
United States

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