From Eastern Europe to South Africa to the Arab Spring, nonviolent action has proven capable of overthrowing autocratic regimes and bringing about revolutionary political change. In fact, recent research suggests that nonviolent movements are more than twice as effective in achieving their goals than violent ones. But these bold findings about nonviolent effectiveness leave open the question of how and when groups choose to initiate a campaign of civil resistance to begin with. Why are some groups able to adopt and sustain a strategy of nonviolent civil resistance while others are either unwilling or unable to do so? Is there anything groups or outside actors can do to increase movements’ abilities to initiate and maintain a nonviolent strategy? This book aims to explain the strategic choices made by movements seeking regime change. My argument is that civil resistance requires challenger organizations to possess certain underlying social network characteristics in order to activate three key mechanisms that are critical to the strategic logic of nonviolent action: mass mobilization, defection, and `backfire’ against repression. Movements lacking social overlap will fail to get a nonviolent campaign off the ground and will be forced to either resign themselves to the political status quo or consider an alternative strategy. Drawing on cases from Nepal and Syria, as well as global cross-national data, the book details the processes through which challenger organizations collect information, deliberate, and decide on whether a strategy of exclusively nonviolent resistance may be viable. I develop a relational theory, showing how the social ties that underpin challenger organizations shape their ability and willingness to attempt regime change using nonviolent means alone.