In reviewing empirical studies on the causes of war, scholars claim to find evidence of progress. Most reviewers, however, do not present a set of explicitly defined criteria and when they do, their criteria are oftentimes ambiguous and vague. The objective of this study is to provide a set of criteria that are clearly defined and then to apply them in a systematic and objective way to one area of conflict studies: the diffusion of war. To do this, I draw upon criteria taken from the works of Kuhn, Popper, Lakatos and Laudan and re-evaluate the progressiveness of empirical studies addressing war diffusion. The criteria I apply include generality, simplicity, precision, predicting novel information, anticipating results and solving both empirical and conceptual problems. My analysis indicates that there is little evidence of progress on most of these criteria. I suggest that perhaps one reason for declining interest in this area is due to the failure of scholars to view the war diffusion research program as progressive. I also argue that social scientists be more explicit and clear in identifying their evaluative criteria so that their resulting evaluations are more objective and rigorous.