The following chapter focuses on the longest-running guerrilla movement in Latin America and, likewise, in the Colombian armed conflict: the National Liberation Army. To this end, it presents its origins and the elements that, from the beginning, have contributed most to defining the particular slant of this guerrilla group. Special attention is paid to the profound transformations experienced in the eighties and nineties when the guerrillas managed, not without difficulty, to overcome significant internal difficulties—and disputes with other armed actors. Their sources of funding and their main territorial anchors are also studied, in order to observe their logic of action, especially coinciding with the turn of the millennium and the arrival of Álvaro Uribe's presidency. With the above, we will finally try to explain the elements of the rise of confrontation and subsequent failed dialogue, both with the presidency of Juan Manuel Santos and that of Gustavo Petro.