The prohibition of attacks expected to cause incidental loss of civilian life, injury to civilians, or damage to civilian objects that would be excessive in relation to the concrete and direct military advantage anticipated lies at the heart of the rules of international humanitarian law (IHL) regulating the conduct of hostilities. According to Article 51(5)(b) of the First Additional Protocol of 1977 to the Geneva Conventions of 1949 (AP I), a disproportionate attack is an attack that may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof that would be excessive in relation to the concrete and direct military advantage anticipated.The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement No 340956 - IOW - The Individualisation of War: Reconfiguring the Ethics, Law, and Politics of Armed Conflict