Abu Bakr ibn Omar (Boubakar), paramount chief of the Lemtouna, defeated Ghana in 1076. His lieutenant and cousin, Yusuf ibn Tashfin, conquered Morocco in 1082 and most of Spain in 1091. The best-known contemporary Mauritanian is Moktar Ould Daddah (b.1924), president from 1961 until 1978; after being ousted, he was eventually allowed to go to France. Lt. Col. Khouna Ould Haydalla (b. Spanish Sahara, 1940) became prime minister and chief of staff of the armed forces in 1978 and assumed the presidency in 1980. Col. Maaouya Ould Sid Ahmed Taya (b.1941), who had been prime minister (1981–84), became president in 1984.