عبد الله بن ياسين
In an attempt to bring about a purer form of Islam among the Sanhaja Berbers, Abdallah ibn Yasin founded the Almoravid movement in present-day Mauritania and Western Sahara. The Sanhaja Berbers, like the Soninke, practiced an indigenous religion alongside Islam. Abdallah ibn Yasin found ready converts in the Lamtuna Sanhaja, who were dominated by the Soninke in the south and the Zenata Berbers in the north. By the 1040s, all of the Lamtuna was converted to the Almoravid movement. With the help of Yahya ibn Umar and his brother Abu Bakr ibn Umar, the sons of the Lamtuna chief, the Almoravids created an empire extending from the Sahel to the Mediterranean. After the death of Abdallah ibn Yassin and Yahya ibn Umar, Abu Bakr split the empire in half, between himself and Yusuf ibn Tashfin, because it was too big to be ruled by one individual. Abu Bakr took the south to continue fighting the Soninke, and Yusuf ibn Tashfin took the north, expanding it to southern Spain. The death of Abu Bakr in 1087 saw a breakdown of unity and increase military dissension in the south. This caused a re-expansion of the Soninke. The Almoravids were once held responsible for bringing down the Ghana Empire in 1076, but this view is no longer credited.