This research studies an attrition rate considering terrain feature in a battlefield. Lanchester-type combat models for heterogeneous forces and the Weapon Effectiveness Index are used in this study. The various environments of the battlefield can be explained by the terrain feature. Attrition rates of heterogeneous model are estimated by applying the battle of Baek-Sek mountain during the Korean War. Estimated attrition rates are checked by the paired samples T-Test. Specific cases are shown in this paper as an example. If we study out the relative influence of the terrain feature upon the performance of individual weapons, these will be a possible alternative to analyze the military operations.