Almoravid dynasty
Due to their military weakness, "taifa" princes appealed for North African warriors to come fight Christian kings on two occasions. The Almoravid dynasty was invited after the fall of Toledo (1085), and the Almohad Caliphate after the fall of Lisbon (1147). These warriors did not in fact help the "taifa" emirs but rather annexed their lands to their own North African empires.