In Children in War, we describe the impact of armed conflicts and war on children and family life and elaborate on ways in which children in and after war can be supported. Attachment theory rooted in the World Wars raging in the 20th century is one of our conceptual underpinnings. The protracted Russian war against Ukraine served as the driving rationale for this Element. Its deleterious effects on child development but also the untold reserves in parents and professionals show that families under siege can profit from support to create safe, stable and shared care for the children. Two developmental scientists recognized for their attachment research and a child psychiatrist working 'in situ' during the war in Ukraine wrote this brief but comprehensive treatise on children and families weathering war. The authors aim to reach researchers but also policymakers and professionals working with children in wartime and its aftermath.