How many interstate and internal wars have taken place recently between whom? How long have they been going on? And how severe are they? How many of these conflicts did take place in the past? And what are the trends? These are crucial questions peace and conflict research has tried to answer for some time now. The data collected for that purpose are relevant both for the scholars searching for explanations and the practitioners trying to prevent these kinds of conflicts in the first place, attempting to resolve them once they have occurred. The problem is that different data collections provide us with different representations of both kinds of conflict: interstate wars and civil wars. These differences are due to differing operational definitions but possibly as well to different theoretical conceptualizations. In order to make that research relevant for politics, replications of the different hypotheses with different data sets are necessary. If the results are robust, these differences would not matter that much. If, however, they are not, which seems to be the case at least for civil wars, the theoretical foundations have to be reconstructed. Only if that has been achieved, can peace and conflict research contribute with greater confidence to the prevention and mitigation of violent conflict.