This paper argues that the concept of the civilian is a specific way of viewing non-combatants that can be traced to the First World War. Before the war, non-combatants were seen by the law and the prevailing culture as citizens. The citizen was potentially and probably aggressive, bound to the fate of his or her state and, therefore, granted only minimal protection by law. The war, however, brought technological changes and a propaganda effort that transformed these citizens into a civilian population. Civilians were essential to the war effort, which meant that they were a target. Yet, at the same time, they were feminized, described as vulnerable and deserving of protection. This cultural shift influenced the way in which the laws of war were understood, leading to the replacement of the traditional categories of law with a military/civilian distinction in the 1923 Hague Draft Rules of Aerial Warfare. In this way the concept of the civilian entered international law.