The Western Sahara War was an armed struggle between the Sahrawi Polisario Front and Morocco between 1975 and 1991, being the most significant phase of the Western Sahara conflict. The conflict erupted after the withdrawal of Spain from the Spanish Sahara in accordance with the Madrid Accords, by which it transferred administrative control of the territory to Morocco and Mauritania, but not the sovereignty. In 1975, Moroccan government organized the Green March of some 350,000 Moroccan citizens, escorted by around 20,000 troops, who entered Western Sahara, trying to establish Moroccan presence. While at first met with just minor resistance by the Polisario, Morocco later engaged a long period of guerilla warfare with the Sahrawi nationalists. During the late 1970s, the Polisario Front, desiring to establish an independent state in the territory, successively fought both Mauritania and Morocco. In 1979, Mauritania withdrew from the conflict after signing a peace treaty with the Polisario. The war continued in low intensity throughout the 1980s, though Morocco made several attempts to take the upper hand in 1989–1991. A cease-fire agreement was finally reached between the Polisario Front and Morocco in September 1991.