This article analyses the history of the military clergy and contrasts its role in the Argentine and Chilean dictatorships on the basis of new, previously inaccessible sources. It is argued here that, in addition to its ideological orientation, two further factors explain differences in the influence of the military clergy on the two regimes: first, the structural position that the Military Vicariates occupied between the Church and the armed forces, and, second, the two dictatorships’ different needs for legitimisation. The analysis provides information relevant to understanding the public role of the Catholic Church and the dimensions of violence during the regimes.