Abu Bakr saw any attempts at recapturing his post politically unfeasible and returned to the fringes of the Sahara to settle the unrest of the southern frontier. Taifa appeal In the year 1091, the last sovereign king of al-Andalus, al-Mu'tamid, saw his Abbadid-inherited taifa of Seville, controlled since 1069, in jeopardy of being taken by the increasingly stronger king of Castile-León, Alfonso VI. The Taifa period followed the demise of the Umayyad Caliphate. Previously, the emir had launched a series of aggressive attacks on neighboring kingdoms, so as to amass more territory for himself, but his military aspirations and capabilities paled in comparison to those of the Castilian king, who in the name of Christendom, in 1085, captured Toledo and exacted parias, or tribute, from Muslim princes in places such as Granada, al-Mu'tamid of Seville being no exception. The tribute of the emirs bolstered the economy of the Christian kingdom, and harmed the Muslim economy. These are the circumstances that led to the Almoravid conquest and the famous quote, rebuffing his son, Rashid, who advised him not to call on Yusuf ibn Tashfin, where al-Mu'tamid said Military exploits Yusuf was an effective general and strategist who put together a formidable army comprising Sudanese contingents, Christian mercenaries and the Saharan tribes of the Gudala, Lamtuna and Masufa, which enabled him to expand the empire, crossing the Atlas Mountains onto the plains of Morocco, reaching the Mediterranean and capturing Fez in 1075, Tangier and Oujda in 1079, Tlemcen in 1080, and Ceuta in 1083, as well as Algiers, Ténès and Oran in 1082-83. He is regarded as the co-founder of the famous Moroccan city Marrakech (in Berber Murakush, corrupted to Morocco in English). The site had been chosen and work started by Abu Bakr in 1070. The work was completed by Yusef, who then made it the capital of his empire, in place of the former capital Aghmāt. By the time Abu Bakr died in 1087, after a skirmish in the Sahara as the result of a poison arrow, Yusef had crossed over into al-Andalus and also achieved victory at the Battle of az-Zallaqah, also known as the Battle of Sagrajas in the west. He came to al-Andalus with a force of 15,000 men, armed with javelins and daggers, most of his soldiers carrying two swords, shields, cuirass of the finest leather and animal hide, and accompanied by drummers for psychological effect.