Generations of scholars have tried to solve the puzzle of why people join rebel groups. Why rebels stop fighting has received much less attention. To stop members from leaving, insurgent groups build high barriers around their organizations, including ideological socialization, in-group solidarity and harsh sanctions. While previous research on desertion has focused on individual motivations to overcome these barriers, we argue that desertion happens more commonly during times of organizational decline, in line with Hirschman’s influential theory on exit. In the case of insurgent groups, organizational decline can derive from loss of military capacity, civilian support, and financial revenues. To test this argument, we use unique data on all reported cases of desertion from the FARC and other non-state armed groups in Colombia (more than 30.000) ranging from 2002 to 2019, provided by the Ministry of Defense. In line with our argument, we find robust evidence that FARC rebels stop fighting more often when their organization enters in decline. These insights complement a rich literature about individual motivations for desertion from armed groups and show that organizational decline can push doubting rebels over the edge.