Western Sahara is recognised by the United Nations as the last non-self-governing territory in Africa. Between 1973 and 1991 it was at war, as the pro-independence Polisario Front fought first against colonial rulers Spain, and after 1975, against Morocco, which invaded with Spanish encouragement. In 1991, a United Nations-sponsored ceasefire was supposed to bring peace, based on a referendum on independence. However, the UN-promised referendum has never been held. Overt support from France, and more tacit support from the US, has enabled Morocco to have it indefinitely postponed.