These events began to lead to political crises in the 1970s, with more frequent land invasions and takeovers of municipal halls. This was the beginning of a process that would lead to the emergence of the Zapatista movement in the 1990s. Another important factor to this movement would be the role of the Catholic Church from the 1960s to the 1980s. In 1960, Samuel Ruiz became the bishop of the Diocese of Chiapas, centered in San Cristóbal. He supported and worked with Marist priests and nuns following an ideology called liberation theology. In 1974, he organized a statewide "Indian Congress" with representatives from the Tzeltal, Tzotzil, Tojolabal and Ch'ol peoples from 327 communities as well as Marists and the Maoist People's Union. This congress was the first of its kind with the goal of uniting the indigenous peoples politically. These efforts were also supported by leftist organizations from outside Mexico, especially to form unions of ejido organizations. These unions would later form the base of the EZLN organization. One reason for the Church's efforts to reach out to the indigenous population was that starting in the 1970s, a shift began from traditional Catholic affiliation to Protestant, Evangelical and other Christian sects.