"Castilian authoritarianism developed from a feudal-military emphasis to one of political control by the Church. During the seven centuries of the Reconquista's uneven course, the Church's role had been mainly that of propagandist for military action, and even of participant. Then, in Isabella's reign the warrior archbishop was superseded by the cardinal statesman. Nevertheless, the connect between Church and army remained close during the rapid growth of Spain's empire when the crucifix was the shadow of the sword over half the world. The army conquered, then the Church integrated the new territories into the Castilain State.
The power which was exerted over the population was an irresistible force, backed by the threat of hell and its earthly foretaste in the form of the Inquisition. A single denouncer, an anonymous whisper from a jealous enemy, was often enough for the Holy Office, and the public confessions extracted before autos-da-fe provided a striking foretaste of the totalitarian sate. In addition the Church controlled every aspect of education and placed the entire population in a protective custody of the mind by burning books to keep out religious and political heresy."The Battle for Spain: The Spanish Civil War 1936 - 1939 by Anthony Beevor.