In Chapter 14, we turn to civil conflict, where the main protagonists are located within a political community. Scale is usually a background condition of little theoretical significance, and scholars have made little effort to theorize its impact on conflict. We begin by presenting a theory of why scale might have a curvilinear effect on civil conflict. While scale decreases social cohesion within a community, and also negatively affects the likelihood of a decisive military victory, it enhances the power of a jurisdiction, decreasing the likelihood that opposition groups will take up arms. We argue that the relationship is likely to be curvilinear because positive scale effects on civil conflict should attenuate quickly while negative scale effects seem likely to continue to grow indefinitely. We proceed to test this theory using a new measure of battlefield casualties, which tracks the number of battle deaths in countries around the world from 1946 to 2009. Our results show that increases in scale enhance conflict, but only up to a certain point. After this inflection point, increases in population are associated with decreases in conflict, proxied by battlefield casualties.