This paper intends to analyze the historical evolution of military involvement in internal security affairs of Mexico since the late 1940s. Recently, many critics have written extensively about Mexico’s heavily militarized policy towards drug trafficking and the organized crime (f.ex: Moloeznik 2010; Manaut 2009; Artz 2003). But without recognizing the historical continuities underlying such policy model, we cannot fully comprehend its origins and effectiveness. Historical-institutionalism is a useful theoretical approach when we are dealing with slow-moving process not captured by a short-time perspective. This approach has emphasized how things that have been institutionalized are inert and un-changed (Mahoney and Thelen 2010). They consider institutions to generate different sets of power distribution that can be changed according to the actors’ will. Pierson (Pierson 2000) in the work “Politics in Time” has argued that since what characterizes science is the discovery of causal relations we should consider time itself as an intervenient variable. In fact, causes and consequences may be separated over time and it may be useful to stretch the temporal horizon of a given analysis.