At the end of the Mexican Revolution in 1920, Mexico's large, rebellious army dominated national politics. By the 1940s, Mexico's Institutional Revolutionary Party (PRI) was led by a civilian president and claimed to have depoliticised the army and achieved the bloodless pacification of the Mexican countryside through land reform, schooling, and indigenismo. However, historian Thomas Rath argues, Mexico's celebrated demilitarisation was more protracted, conflict-ridden, and incomplete than most accounts assume. Civilian governments deployed troops as a police force, often aimed at political suppression, while officers meddled in provincial politics, engaged in corruption, and crafted official history, all against a backdrop of sustained popular protest and debate.

Using newly available materials from military, intelligence, and diplomatic archives, Rath weaves together an analysis of national and regional politics, military education, conscription, veteran policy, and popular protest. In doing so, he challenges dominant interpretations of successful, top-down demilitarisation and questions the image of the post-1940 PRI regime as strong, stable, and legitimate. Rath also shows how the army's suppression of students and guerrillas in the 1960s and 1970s, and the more recent militarisation of policing, have long roots in Mexican history.