Acts of war and terrorism are increasingly prevalent in contemporary society. Throughout history, weaponry has become more efficient, accurate, and powerful, resulting in more devastation and loss of human life. Children are often overlooked as victims of such violence. Around the world, children are exposed to violence in multiple forms, frequently developing traumatic stress reactions. Such reactions are best understood within the context of social-emotional and cognitive development, as children respond differently to the stress of violence depending on their developmental level. Furthermore, the violence of war and terrorism often results in a multitiered cascade of negative life events including loss of loved ones, displacement, lack of educational structure, and drastic changes in daily routine and community values. These numerous losses, challenges, and stresses affect children's brains, minds, and bodies in an orchestrated whole-organism response. This paper describes these effects, synthesizing the current state of research on childhood traumatic stress reactions from the fields of neuroscience, clinical psychology, and pediatric diagnostic epidemiology.