This paper highlights the importance of natural resource concentration and ethnic group regional concentration for ethnic conflict. The existence of multiple conflict terrains (and hence multiple threat points) is the source of bargaining failure, similar to the one determined by the presence of offensive advantages. The theory predicts war to be more likely when resource and group concentration are high, and the empirical analysis, both at the country level and at the ethnic group level, confirms the essential role of geographic concentration variables for civil war.