The zone was established as a Polisario-held zone in a 1991 cease-fire between the Polisario Front and Morocco, which had been agreed upon together as part of the Settlement Plan. Morocco controls the areas west of the Berm, including most of the territory's population. The cease-fire is overseen by the United Nations' MINURSO forces, charged with peacekeeping in the area and the organization of a referendum on independence.[2]