According to the dominant narrative in international humanitarian law, the 1949 Geneva Convention on Civilians is part of the discipline’s humanitarian progress, driven by the International Committee of the Red Cross, in response to atrocities committed during World War II. This paper argues that historical research enables a more nuanced historical account which challenges when, how and by whom the protection of civilians was developed. It demonstrates that the Convention’s protection regime was shaped by the efforts of a variety of non-state actors during the inter-war years. In particular, it focuses on attempts by the International Committee of the Red Cross, International Law Association and International Committee of Military Medicine and Pharmacy to advance the law independently and in cooperation in relation to ‘enemy civilians’ and safety zones after World War I. However, it suggests that these actors were to some extent inhibited by conceptual limitations and self-restraint, which ultimately led to some of the weaknesses in the protection regime under the 1949 ‘Civilian Convention’. The paper thus reveals the struggle over the conceptualisation of individuals who are today considered civilians in the inter-war years which is embedded in the text of the adopted treaty.