Why do combatants uproot civilians in wartime? In this paper I identify cross-national variation in three population-displacement strategies—cleansing, depopulation, and forced relocation—and test different explanations for their use by state actors. I advance a new “assortative” theory to explain forced relocation, the most common type. I argue that combatants displace not only to expel undesirable populations, but also to identify the undesirables in the first place by forcing people to send signals of loyalty and affiliation based on whether, and to where, they flee. This makes communities more “legible” and facilitates the extraction of rents and recruits. I test these arguments using a novel Strategic Displacement in Civil Conflict data set (1945–2008). Consistent with my expectations, different displacement strategies occur in different contexts and appear to follow different logics. Cleansing is more likely in conventional wars, where territorial conquest takes primacy, while forced relocation is more likely in irregular wars, where identification problems are most acute. The evidence indicates that cleansing follows a logic of punishment. The results for relocation, however, are consistent with the implications of my assortative logic: it is more likely to be employed by resource-constrained incumbents fighting insurgencies in “illegible” areas—rural, peripheral territories. A case study from Uganda based on in-depth fieldwork provides evidence for the assortative mechanism. As the most comprehensive analysis of wartime displacement strategies to date, this paper challenges some core assumptions about a devastating form of contemporary political violence.