This paper examines the role of external support overtness in shaping rebel violence againstcivilians in intrastate conflict, using a time-series comparison of the United States’ support tothe Contrarevolucionarios in the Nicaraguan Contra war during its covert phase (1981-1984)and overt phase (1985-1990) of support. The central hypothesis posits that higher levels ofovertness in external state support to rebel groups reduce the likelihood of civilianvictimization in civil war. Although the within-case comparison offers valuable insights intothe theoretical framework, the analysis reveals that overtness alone is insufficient to explainthe observed outcome, as no significant variation in civilian victimization was identifiedacross the temporal units. Instead, factors such as fluctuation of aid, guerilla warfare tacticsand the Contras’ organizational structure emerged as important alternative explanations.These findings highlight the need for future research to explore the interplay betweenexternal dynamics and contextual factors in shaping patterns of rebel violence againstcivilians in intrastate conflict settings.