Cohesion is defined as the creation and maintenance of cooperative effort towardsthe attainment of the organization’s goals. This paper argues that existing theories of cohesion in the military are deficient. For most soldiers, patriotism and ideology play only a diffuse an indirect motivational role. Explanations based on selective incentives and primary group solidarity also suffer from theoretical and empirical inconsistencies. This paper maintains that the more individual soldiers self-identify as members of an armed organization over other putative identities, the greater will be organizational cohesion. While the military provides individuals with a sense of belonging to an entity greater than the face-to-face primary group, it also provides a means of status distinction within, as opposed to across communities. Three mechanisms by which organizational socialization is strengthened are identified: training, ritual, and collective burden sharing. Evidence from the U.S. Army in Vietnam and the Wehrmacht in the Second World War suggests that the latter may be especially significant. Soldiers kill and die, not for society as a whole, but for an imagined community of fellow warriors, an imaginary brotherhood.