From my basic understanding the Western Sahara area was previously controlled by Spain which Morocco claimed as part of its' historical territory. The consensus in the region was that the pro-independence Polisario Front formed in 1973 was the legitimate representative of the Sahrawi people who were engaged in armed conflict with the Spanish. Morocco annexed the territory in 1975 and Spain ceded control of it to them, which the Polisario Front resisted. Generally Morocco has been trying to get its' control of the Western Sahara recognized. For example normalizing relations with Israel in exchange for Israel recognizing its' claim to the region.