Although a century has passed since its outbreak, the First World War retains much of its mystery.

Historians have long debated its origins. But now it is the very violence of the conflict that focuses many of their discussions: its intensity; its specificity, if we compare the First World War to the wars that preceded it; or even the way in which combatants and civilians succeeded in holding on for so long, in almost unbearable living conditions.

Violence on the battlefields, violence against civilians, the violence of weapons and of words: the first global conflict marks a major rupture in the history of modern warfare, precisely because it abolished any distinction between combatants and non-combatants. To understand the intensity of total war, military historians first had to move away from a ‘history from above', from the perspective of statesmen, strategists and generals, and instead study how the violence of war impacted bodies and minds. This first historiographical revolution occurred in the 1970s, when John Keegan published his groundbreaking book The Face of Battle.^{[454] [455]} More recently, military historians have explored the impact of the war on civilian populations (the Armenian genocide; the bombing of cities; blockades and famine; the dis­placement of refugees; sexual violence...) and reflected on the way in which stirring discourse allowed societies at war to endure the conflict. Indeed, the violence of the First World War was enacted not only by nation states, armies, police forces and administrations, but also by individuals, or groups of individuals, acting spontaneously or under constraint in support of their homeland. It consisted not only of violent acts, but also of violent images and words. Studying the links between the discourse and practice of violence is one of the important aspects of the history of war cultures, which has been developed by historians since the late 1990s.^[456]

Last but not least, thinking about the violence of the First World War means interrogating its place in the history of modern warfare: the emer­gence of industrial warfare in the second half of the nineteenth century; the thresholds of violence breached one by one in 1914-18; and finally, how the violence of war was transformed (far more than it was dissipated) in the transition from war towards peace. In other words, it requires redefining what we commonly call ‘wartime': the individual and collective initiation into violence; thresholds of violence and the way they are perceived; how forms of violence mutate; the rhythms and modalities of demobilisation; and finally, the future of war violence after the official cessation of hostilities.