Abstract: This study investigates the use of casualty based entropy and the entropic phase space developed by Carvalho-Rodrigues et al, to determine its usefulness as a measure of effectiveness without further investigation into the theoretical meaning of the method. The change in combat entropy (ΔS) method for time-independent data of Carvalho-Rodrigues et al was tested using historical analysis. We then extended the ΔS method and showed its utility for time-dependent data, where Carvalho-Rodrigues et al applied an entropic phase space (EPS). While the entropic phase space was determined to be a poor outcome predictor we found that the ΔS between two forces is a good predictor of attrition based warfare outcomes with a successful force usually one that can maintain lower entropy for a greater time period.