The Settlement Plan was an agreement between the ethnically Saharawi Polisario Front and Morocco on the organization of a referendum, which would constitute an expression of self-determination for the people of Western Sahara, leading either to full independence, or integration with the Kingdom of Morocco. It resulted in a cease-fire which remains effective to this day, and the establishment of the MINURSO peace force to oversee it and to organize the referendum. The referendum never occurred. Background The area of Western Sahara is home to the Saharawi people who became Spanish subjects when Spain colonized the area in 1884. The United Nations (UN) became involved with Western Sahara when the UN asked Spain on December 16, 1965, through a General Assembly resolution, to decolonize the former Spanish territory. King Hassan II of Morocco rejected claims of independence for Western Sahara as early as 1975, despite International Court of Justice findings that Morocco did not have legal ties to the area. However, a Moroccan rule of the area can be traced to Islamic expansion in the area, starting with the Midrarid dynasty (823-977 AD). In October 1975, King Hassan ordered an invasion of Western Sahara, and the United States pressured Spain to withdraw. After Spain withdrew from Western Sahara in 1976, an ongoing dispute began between the former territory and Morocco. In November 1975, Moroccan troops, ordered by King Hassan, lead 350,000 civilians into Western Sahara in order to "seize the territory for Morocco" in the Green March. After the march, Spain divided the territory between Morocco and Mauritania. The Polisario Front was formed by Saharwi people in 1973. The group started fighting for the independence of Western Sahara. The group has been backed by Algeria. Polisario's fight for independence caused Mauritania to relinquish its claim on Western Sahara in 1978. In August 1979, Mauritania signed a peace agreement with Polisario and when Mauritania withdrew, Morocco took up occupation of that land as well. Until 1991, when a cease-fire was brokered, Polisario Front ran a guerrilla war against the Moroccan Army. Over a period of thirty-five years, "over 100,000 Saharawis have been displaced from the area." Because of the lack of agreement, the Saharwi people's voice in the matter has been marginalized, according to Toby Shelley, writing in the Middle East Report. The territory of Western Sahara also plays a part in the struggle of Algeria and Morocco over "regional preeminence"