Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Political Science, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 658-681).The internal unity and discipline of insurgent groups helps us understand the military effectiveness of armed groups, patterns of violence against civilians, and the ability of insurgent organizations to negotiate and demobilize, but the causes of insurgent cohesion and fragmentation have not been systematically or comparatively examined. This study offers a theory to explain why some armed groups are more cohesive and controlled than others. It argues that the trajectories of insurgent organizations can be substantially explained by focusing on two variables: the structure of the social networks and institutions upon which the organization is built, and the organization's access to material resources from outside the war zone. First, the structure of the core networks upon which an organization is constructed determines the internal social environment of the group: its social base shapes its organizational form. The denser the core networks, and more tightly they pull together local communities, the more robust will be the organization that emerges. Social embeddedness can therefore be more important than mass political popularity, public goods provision, or ideology in providing the basis for enduring organizational cohesion. Organizations built around coalitions of localized pockets of collective action or leaders operating among populations with whom they lack social ties will face severe problems of internal control - regardless of organizational blueprints or ethnic and class appeals. Second, external material support from states and diasporas tends to centralize internal control and to enhance insurgent military power. Rather than encouraging looting and thuggishness, resource-wealth can fuel highly cohesive and disciplined armed organizations. The interaction of social bases and external support generates empirically distinct trajectories of organizational cohesion. Mechanisms explaining change over time are derived from the structural underpinnings of this argument. This theory is tested with a study of 26 armed groups in nine civil wars. The primary research design is a set of within-conflict comparisons of insurgent organizations in civil wars in Kashmir, Northern Ireland, and Sri Lanka. Within each war there is dramatic variation across groups within a shared structural context. Fieldwork, primary sources, and secondary sources are used to trace out the different trajectories of militancy and their origins. An external validity check is provided by a study of Southeast Asia, relying on a cross-national comparison of communist insurgents in Malaya, Vietnam, and the Philippines, a sub-national, cross-conflict comparison of armed groups in Aceh and East Timor, and a within-conflict comparison of separatists in the southern Philippines. These comparisons reveal strong support for the theory relative to its competitors while also uncovering new mechanisms of change and evolution.by Paul Stephen Staniland.Ph.D