In December 1969, former President Lázaro Cárdenas sent a letter to political prisoners in the Lecumberri federal penitentiary in Mexico City, assuring them that he would continue to lobby for their release. In October 1973, Michoacán university students marching in front of the state government building in Morelia held up placards demanding the release of political prisoners. On June 29, 1974, Lucio Cabañas, guerrilla leader of the Partido de los Pobres (Party of the Poor) in the mountains of Guerrero, released a communiqué in which the group's first demand was the release of political prisoners. In its founding document from March 1973, the Liga Comunista 23 de Septiembre (LC-23S), an urban-based guerrilla group responsible for more than 60 direct-action operations, made it clear that political prisoners were one of the costs of carrying out a revolution and, as such, would not distract from its broader mission. These are just some of the references to the imprisonment of activists during the height of what is considered Mexico's dirty war. Taken together, the many references to political prisoners suggest that being held captive by the state was a common threat and, in some cases, a reality in the lives of those challenging the authoritarian government in the 1960s and 1970s.