One of the most prolific revolutionary writers in Latin America during the 1960s and intellectual mentor of Uruguay's revolutionary Movement of National Liberation (Tupamaros), he is most widely known as the author of Strategy of the Urban Guerrilla, which played an important role in the activities of urban guerrillas in Uruguay, Argentina, and Brazil.

During the Spanish Civil War he fought against the Francisco Franco's forces, operating within the National Confederation of Labour (CNT), the Iberian Anarchist Federation (FAI), and the General Union of Workers (UGT).

At the end of the war, he was arrested by Franco's forces, condemned to death, and ultimately was sentenced to ten years in prison.

During the Perón era, he worked as an editor for Economia y finanzas ("Economy and Finance"), and his contributions were published under the pseudonym, Jaime de las Heras.

In addition to Argentina and Uruguay, he also lived and worked in Peru and eventually returned to Madrid, Spain, where he taught theories of economic self-management and communal political action.