Perhaps the simplest explanation for where fault lines lie in a political process involves the presence of an "other." Difference divides and similarity unites. These similarities and differences can in turn orient and propagate conflict. Yet, similarity and difference are also dynamic, evolving in response to changing population characteristics or a new reference point. We offer a simple explanation for interstate conflict in which the salience of similarity or difference varies with the prevalence or capabilities of groups. We apply our argument in the context of the democratic peace. When democracies are scarce or weak, and autocracies plentiful and powerful, democracies face a common threat. As the democratic community strengthens, however, the threat from autocracies declines and differences among democracies appear more salient. Our findings contrast with standard expectations about how democratization shapes world affairs.