This book is concerned with the nexus between warfare and welfare. The relationship between war and welfare states is contested. While some scholars consider war a pacemaker of the welfare state, others have emphasized a sharp trade-off between ‘guns and butter’ and highlighted the negative impacts of war on social protection. However, many of these findings only focus on social spending or are based on studies of individual national cases. From a comparative and interdisciplinary perspective, this book addresses the question of whether and how both world wars have influenced the development of advanced welfare states. Distinguishing between three different phases (war preparation, wartime mobilization, and the post-war period), the volume provides the first systematic comparative analysis of the impact of war on welfare state development in the Western world. The chapters, written by leading scholars in this field, examine both short-term responses to and long-term effects of war in fourteen belligerent, occupied, and neutral countries in the age of mass warfare stretching over the period from c.1860 to 1960. The findings clearly show that war is essential for understanding several aspects of welfare state development and welfare state patterns in advanced democracies.