The social costs of war: investigating the relationship between warfare and intragroup violence during the Mississippian period of the Central Illinois Valley

War exacts a great social cost, not only upon its direct participants, but also upon the lives of the friends, family, and community of those who experience it. This cost is particularly evident in the increased frequencies of aggressive behaviors, including homicide, assault, and domestic violence, enacted by Western military veterans with posttraumatic stress disorder (PTSD).