This thesis examines the theory and practice of sustaining peace after an intrastate conflict. After an agreed-upon peace settlement is signed, certain factors support sustaining the peace, and for this study those factors are analyzed to develop recommendations for implementation in Colombia. Drawing from literature on peace settlements and case studies, the thesis posits that the positive factors for sustainable peace be employed to function as a plan to deter a recurrence of intrastate conflict. The thesis tests these factors through analysis of the period following civil wars in Angola and Mozambique and finds that political inclusion and public security are particularly important. In Colombia, the Marines, along with the backing of the United States Armed Forces, will aim to sustain the peace through collaboration. Building on these findings, this thesis recommends ensuring that disarmament, demobilization, and reintegration DDR and security sector reforms SSR are the foundations for sustaining the peace.