The following work analyses the process of defeat, at a national level, but also internationally, experienced by the National Liberation Movement—Tupamaros (MLN-Tupamaros) throughout 1972. It looks at a number of factors, but, above all, it addresses the process by which the foundations of the Uruguayan urban guerrilla movement began to deteriorate and lose their character in 1970. In this way, many of the theoretical and discursive contradictions are presented which, in the end, blur the revolutionary approaches designed in the mid-sixties by its founding members. To fulfil this purpose, numerous documents produced by the Tupamaros are used, as well as government files from the Ministry of Defence. Likewise, accounts from leaders and recognised members of the MLN-T who experienced the almost sudden process of military defeat first-hand are included.