The 19th of April Movement was the first of many guerrilla groups in Colombia to start a negotiation process that concluded in a final peace agreement involving its demobilisation as an armed group and leading to some of its members founding a new political party, the Democratic Alliance M19. This not only paved the way for seven other groups to start peace negotiations and ultimately transform from armed to political actors. This study combines interaction between first-hand experience and academic knowledge of this peace process. The study is divided into four sections. The first explores the context in which M-19 emerged, the reasons for its appearance and the way in which it engaged in armed struggle as a political-military movement. The second section considers the internal and external factors that pointed this guerrilla group towards the path of peace. Section 3 analyses the way in which M-19 entered the peace process, negotiated a political agreement and subsequently formed a legitimate political movement that participated in electoral life. A final section draws out the results of this process, highlighting some lessons that could be relevant to other groups who consider a similar path.