Between 1975 and 1991, the Moroccan Armed Forces fought a 16-year war against the POLISARIO, an Algerian backed rebel national liberation movement seeking the independence of Western Sahara from Morocco. From the mid-1980s on, Morocco largely managed to keep POLISARIO troops at bay by building a huge sand wall, staffed by an army roughly the same size as the entire Sahrawi population, enclosing the Southern Provinces within it. The enclosure contained most of the economically useful parts of Western Sahara, including Bou Craa, El-Aaiun, and Smara. The Moroccan army destroyed all the posts created by the Polisario and won decisively the majority of battles, but artillery strikes and sniping attacks by the guerrillas continued, and Morocco was economically and politically strained by the war.