Macro-level accounts of the relationship between identity and action in civil war typically analyse a small number of highly polarized and politicized identity categories associated with a conflict’s master cleavage. In contrast, micro-level accounts routinely point to the existence of myriad local cleavages and the associated proliferation of personal rivalries. In an effort to bridge the divide between these micro-and macro-level depictions, this paper specifies a mechanism by which: (i) local cleavages lose autonomy and merge into a central cleavage; and (ii) a central cleavage fragments into highly localized and personal cleavages. Our computational model of cleavage dynamics in civil wars demonstrates that the twin processes of ethnic homogenization and fragmentation may be understood as arising from the same underlying mechanisms. Specifically, we model how the ‘tags’ of agents closely arrayed in identity space cease to serve as a reliable indicator of group behavior, and conversely, how dissimilar tags come to be perceived as related—with attendant implications for the organization of conflict. We depict the spatial patterns associated with these divergent trajectories of mutual identification and de-identification in three cases: the Georgian–Abkhazian conflict (1992–1993), the first Liberian civil war (1989-96), and armed conflict in Colombia (1966-).
