There are currently over 100 stateless nations pressing for greater self-determination around the globe. The vast majority of these groups will never achieve independence. Many groups will receive some accommodation over self-determination, many will engage in civil war over self-determination, and in many cases, internecine violence will plague these groups. This book examines the dynamic internal politics of states and self-determination groups. The internal structure and political dynamics of states and self-determination groups significantly affect information and credibility problems faced by these actors, as well as the incentives and opportunities for states to pursue partial accommodation of these groups. Using new data on the internal structure of all self-determination groups and their states and on all accommodation in self-determination disputes, this book shows that states with some, but not too many, internal divisions are best able to accommodate self-determination groups and avoid civil war. When groups are more internally divided, they are both much more likely to be accommodated and to get into civil war with the state, and also more likely to have fighting within the group. Detailed comparison of three self-determination disputes in the conflict-torn region of northeast India reveals that internal divisions in states and groups affect when these groups get the accommodation they seek, which groups violently rebel, and whether actors target violence against their own co-ethnics. The argument and evidence in this book reveal the dynamic effect that internal divisions within SD groups and states have on their ability to bargain over self-determination. Kathleen Gallagher Cunningham demonstrates that understanding the relations between states and SD groups requires looking at the politics inside these actors.