Limiting Killing in War: Military Necessity and the St. Petersburg Assumption

Ethics & International Affairs (2013), Vol. 26 (3), 311-333

31 Pages Posted: 19 Apr 2019

See all articles by Janina Dill

Janina Dill

University of Oxford

Henry Shue

University of Oxford

Date Written: 2012


Over the last decade, conventional just war theory has been systematically and thoroughly unraveled by a group of philosophers sometimes collectively referred to as the “revisionist critics.” Given the antagonism between the conventional and the revisionist camps, it is rarely recognized that their most prominent representatives, Michael Walzer and Jeff McMahan, respectively, share the assumption that the form of the rules of war can be explained by an underlying retention or forfeiture of moral rights by individual persons. Walzer treats combatants on both sides as morally equal — that is, equal in moral rights; and McMahan treats them as morally unequal as a result of their own individual conduct — that is, as displaying different degrees of moral liability to defensive harm as a result of features of their decision to participate in war and of their conduct in that war. Both maintain that there can be a rational connection between the moral status of individuals (moral equality for Walzer and differential “moral liability to defensive harm” for McMahan) and how they are permitted to be treated during combat.

The persistent controversy between conventional and revisionist just war theorists (as well as among the latter) centers on whether a direct connection between the practical rules for conduct in war and fundamental moral prescriptions about the preservation of individual rights is possible and, if so, how closely the former can follow the latter. Walzer allows for considerable space between what he refers to as “the war convention,” on the one hand, and ordinary morality, which he reserves for “peace-time activities,” on the other hand. The war convention ensures that intentionally inflicted harm is limited to combatants, a category that is loosely connected to individuals’ higher threat potential and possibly their consent to being put in harm’s way, which in war, according to Walzer, warrants forfeiture of the combatants’ right to life. McMahan believes in the possibility of a much smaller disconnect between law and “deep morality,” which he maintains is the same in war and in peace. In his view, rules for warfare should strive to distribute harm as much as possible in accordance with the liability of individuals. For a while now, this debate has provided the main axis around which most research in the area is conducted and along which new ideas are situated.

Though neither camp would contest that the best available rules for war cannot perfectly track and fully preserve all individual rights that we respect in peace, we consider it important to challenge even their abstract premise: that individual rights is what rules for warfare should be geared directly toward. Instead, we argue that the best available rules for conduct in war explicitly depart from moral prescriptions regarding individual rights. In the morally tainted environment that is war, the best available rules center on allowing only violence that is necessary for a war to be waged. The military necessity of individuals’ engagement in the fighting, not their moral status, should determine whether or not they are immune from attack.

Keywords: IHL, Just War Theory, military necessity, distinction, moral liability to harm, revisionism

Suggested Citation

Dill, Janina and Shue, Henry, Limiting Killing in War: Military Necessity and the St. Petersburg Assumption (2012). Ethics & International Affairs (2013), Vol. 26 (3), 311-333, Available at SSRN:

Janina Dill (Contact Author)

University of Oxford ( email )

Manor Road
Oxford, OX1 3UQ
United Kingdom

Henry Shue

University of Oxford ( email )

Mansfield Road
Oxford, Oxfordshire OX1 4AU
United Kingdom

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