Starting from when the Cuban Revolution managed to overthrow Batista in 1959, there were episodes of armed conflict in the Southern Cone against States which more or less restricted freedom. If initially the guerrilla tactics were carried out exclusively in rural areas, with the emergence of the Movimiento de Liberación Nacional-Tupamaros, tactics were extended to cover urban areas. Montevideo was the first city to experience this new technique of political violence which the Tupamaros described in several of their publications. In Argentina, a few years later. Montoneros a group with peronist leanings, in an attempt to emulate their neighbours, embarked on a series of armed actions aimed at destabilizing the country. The reaction of the South American States did not take long in coming; with the backing of the United States, some of them carried out the so called Condor Operation, an oppressive action which, included the utilization of criminal means, and which put an end to the guerrilla groups in the continent. In this article, an analysis (based on original documentation) will be made of the urban guerrilla techniques, the influence between Tupamaros and Montoneros (two among the most well-known groups dealing in this kind of guerrilla warfare in cities), the link between the most active armed groups in South America and the repression on the part of the some governments by way of the Condor Operation. [ABSTRACT FROM AUTHOR]