Through an analysis of unpublished foreign military sources, this article examines the conflictive relations between Peruvian civilians and members of the military during a civil government: the Oncenio of Augusto Leguía (1919-1930). The classic question about South American military forces —Why they carry out coups d’etat so often?— is substituted by another, much broader one: How did they function politically? In the early 1920s, the Peruvian army was fragmented: some officers supported the central government and others opposed it. Those that supported the regime were rewarded, while those who took action against it did so outside of Lima, frequently hand-in-hand with civilian leaders, guided by officers of the rank of lieutenant coronel and below, and probably in reaction to measures taken by president Leguía against the army as an institution or against specific officers.