Abraham Guillén was an author, economist, educator. One of the most prolific revolutionary writers in Latin America during the 1960s and intellectual mentor of the 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. Guillén was born in Guadalajara on March 13, 1913. During the Spanish Civil War he fought against the Franco's forces, operating within the National Confederation of Work (CNT), the Federation of Spanish Anarchists (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. He escaped from prison in 1945, fled Spain, and spent three years in France.