Tresviso I (La Mesa), Cantabria (2016). After the fall of the northern front on 21 October 1937, many fighters fled to the Asturias mountains, forming guerrilla groups in the most rugged areas such as the Liébana Valley.Areces I (Field of the Basques), Las Regueras, Asturias (2016). Las Regueras, Asturias. A dovecot stands beside a trench where locals buried some 80 soldiers of the Basque army. The wounded from an improvised field hospital were murdered around noon on 23 February 1937 – mostly by bayonet.