Proportionality in Perspective: Historical Light on the Law of Armed Conflict


“Proportionality” – the doctrine that military attacks must not cause “excessive” harm to civilian life and property – was not mentioned in any international convention on the law of armed conflict until Additional Protocol I (1977). Commentaries by the Red Cross depict AP I’s rule as a return to traditional understandings, implicitly repudiating their abandonment by the western Allies in the Second World War. The historical record is quite different. Leading commentators before the Second World War endorsed food blockades and massive destruction of infrastructure. American military commentators, down to the 1970s, assessed World War II practice as broadly consistent with international law. At the time it was negotiated, AP-I was not seen as a radical departure from Twentieth Century practice. It should not be interpreted to impose disabling constraints on contemporary military action. Different military challenges justify different levels of harm to civilians. The context of military action must matter as much as any abstract formula like “proportionality.”