When he returned to Chile in 1969 with a Major's degree, he taught Intelligence classes at the Tejas Verdes School of Engineers. In 1970, he was appointed Secretary of the Army General Staff. In 1971, he was director of the Engineer Regiment No. 4 Arauco in the city of Osorno. It is in this period that, together with a group of colonels and captains, he began to collect information and design an intelligence apparatus capable of infiltrating and dismantling leftist organizations. Contreras had a group of informants in Chile from right-wing parties and groups such as the Nationalist Front Fatherland and Liberty (Frente Nacionalista Patria y Libertad, FNPL), at the same time that he maintained contacts with agents of the CIA and the Naval Intelligence Office in Valparaíso and San Antonio who operated in Chile in In that period, it was the latter who provided him with manuals for the secret police of various countries, such as the KCIA of South Korea, the SAVAK of Iran and the National Information Service of Brazil.