The intention of this thesis is to explore the factors that led to the success of two Latin American revolutions in Cuba (1959) and the Sandinista Revolution in Nicaragua (1979). While insurgent movements have proliferated in Latin America since the Spanish "conquest," these are the only two that, in the post-World War II era, have taken power by overthrowing the incumbent regimes by force of arms. Understanding the most prominent factors that led to the success of these revolutions will aid in identifying the potential for success of current and future insurgents. This thesis hypothesizes that the four critical factors that contributed to the success of the Cuban and Nicaraguan revolutions are leadership (strategy), popular support (the ability of the insurgents to assemble a popular constituency for their message and program), external factors (degree of support in the international environment), and military impact (the personalistic, repressive, corrupt, and unprofessional armed forces). In other words, an analysis of these four factors as they relate to both revolutions will provide the best critical approaches to explain success.