This article examines how the production of a dividing line, through violence, the accompanying narratives, and the policing of a physical border from 1991 to 1995, shaped and influenced the lives of ordinary people, all residents of Western Slavonia. How was it possible for people to be divided so abruptly and effectively in a community with a history of multiethnic solidarity? How were these new social divisions produced and reproduced over the course of warfare on a social level? By considering new archival sources, in-depth interviews, and recent scholarly publications, this study argues that such dividing line made the process of ethnicization, or of polarization, possible. Thus, by representing the space where the top-level political cleavages, local-level cleavages, and individuals’ beliefs and momentary choices meet, the wartime dividing line effectively transformed former neighbors into political enemies who were no longer familiar, visible, or accessible on a human level.