This Brief provides a comprehensive introduction to current research on armed groups and proposes a unitary political theory for their future analysis. Traditionally, theoretical and historical approaches to armed groups have focused on different categories of armed groups—insurgents, radical groups, militias, governmental forces—instead of treating them as unitary actors in international politics. This Brief departs from this traditional theoretical treatment, arguing that armed groups are fundamental units of politics, outside of class, gender, and the state, and should be analyzed as such. The book begins with a discussion of current classifications and definitions of armed groups as well as methodological approaches towards studying them. Chapter Two discusses armed groups from a historical and anthropological perspective. Chapter Three presents a critical analysis and interpretation of existing political perspectives on armed groups. The book concludes by introducing thenew theory. Challenging traditional methods of political theory and analysis while providing a solid introduction to the field, this Brief will be of use to researchers and scholars in political theory, international relations, political science, and anthropology, as well as to professionals in fields such as policing, counter-terrorism, and internal affairs.