Previous studies of the cohesion of organized armed groups (OAGs) have made great progress, but they have mostly focused on units fighting for modern Western states. I argue that the study of OAGs that contain their own legitimacy requires a broadened theoretical framework. Such groups may be conceptualized as “ruling organizations” in Max Weber’s terminology. Examples of such groups range from early medieval warbands to modern militias and guerrillas. Members of ruling organizations obey commands for a combination of three reasons: rational, traditional, and charismatic—these in turn form the basis of the legitimacy of the organization. Pinpointing the foundations of obedience in a group provides us with another way of emphasizing weak points that we want to either target or reinforce. This study contributes theoretically to the study of cohesion by linking it to theories of legitimacy in political orders.