This edited volume brings together historians, sociologists, and demographers from across Europe to shed light on three specific aspects of the impact of The Great War on the life courses of “ordinary” citizens. Chapters investigate key aspects of marriage (1) and divorce (2), using these as a window into gender relations (3). They do so by placing WWI in the context of the demographic history of the first thirty years of the twentieth century. Looking beyond the macro-demographic trends and counts, they unveil the countless individual life histories that lie underneath, and that often took unexpected turns. Records on marriage and divorce allow for reconstruction of the life histories of men, women, and children that lived through the war. Thereby, they show in what ways the war impacted on crucial aspects of the life course, such as whether or not women contracted a marriage; at what age, and with what kind of spouse; whether or not they had children; and how they kept their marriage intact. They also provide unique opportunities to study heterogeneity in the effects of the First World War, and in the intensity of these effects, on different subgroups within populations, for example heterogeneity by socio-economic status, gender, and age.