My dissertation centers on the threats to peace in countries emerging from armed conflict. I focus on the case of Colombia, where a 2016 peace agreement with a leftist guerrilla group called the FARC has been threatened by the emergence and expansion of dissident FARC factions that reject peace. In the first chapter, I investigate the origins of these dissident groups, using observational data to explain their pattern of expansion. In the second chapter, I focus on the short and medium-term consequences of violence by dissident factions on the peace process, showing how their emergence has disrupted the rebel demobilization and resulted in violence against former combatants. In the third chapter, I use survey and experimental evidence to understand the long-term consequences of these setbacks to peace, testing specifically on how they affect public support for peace agreement implementation and future negotiations. My dissertation research has received generous funding from the IGCC's Dissertation Fellowship as well as the UCLA Political Psychology Fellowship.