يوسف بن تاشفين
Under Yusuf ibn Tashfin, the Almoravids were invited by the Muslim "taifa" princes of Al-Andalus to defend their territories from the Christian kingdoms. Their involvement was crucial in preventing the fall of Al-Andalus. After having succeeded in repelling Christian forces in 1086, Yusuf returned to Iberia in 1090 and annexed most of the major "taifas".