Discussions about ethnic mobilization in eastern Europe have emphasized efforts of nationalist leaders to demarcate their community from their neighbors in mixed areas where ethnic boundaries and identities were blurred. Demarcation became a common means of defining the community both geographically and culturally, a process which later facilitated the community's mobilization. In the German Empire, however, the Polish-German demarcation was already stark, since it mostly coincided with Catholic-Protestant demarcations. But while the Polish community mobilized quickly and showed great solidarity, the German community did not. Using the Bromberg/Bydgoszcz administrative district as a model, the article argues that the local German community's internal divisions limited its ability to mobilize. Germans agreed on the need for greater German community solidarity, but differed on conceptualizations of its ideal structure and form. Liberal nationalists, envisioning a more egalitarian community defined by a common ethnicity, fought with local conservatives, who were as intent on preserving their prominence within the community as they were on struggling with the Poles. Such divisions crippled local German mobilization on any scale comparable to their Polish neighbors, suggesting that an ethnic community's self-demarcation is necessary but not sufficient to ensure its mobilization.