Morocco, Western Sahara, and Mauritania under Almoravid control. He spent at least several years capturing each fort and settlement in the region around Fez and in northern Morocco. After most of the surrounding region was under his control, he was finally able to conquer Fez definitively. However, there is some contradiction and uncertainty among historical sources regarding the exact chronology of these conquests, with some sources dating the main conquests to the 1060s and others dating them to the 1070s. Some modern authors cite the date of the final conquest of Fez as 1069 (461 AH). Historian Ronald Messier gives the date more specifically as 18 March 1070 (462 AH). Other historians date this conquest to 1074 or 1075. In 1079 Ibn Tashfin sent an army 20,000 strong from Marrakesh to push towards what is now Tlemcen to attack the Banu Ya'la, the Zenata tribe occupying the area. Led by a commander named Mazdali Ibn Tilankan, the army defeated the Banu Ya'la and executed their leader, Mali Ibn Ya'la, but did not push to Tlemcen right away. Instead, Ibn Tashfin himself led an army in 1081 that conquered Tlemcen, massacring the Maghrawa forces there and their leader, al-Abbas Ibn Bakhti al-Maghrawi. He pressed on and by 1082 he had captured Algiers. Ibn Tashfin subsequently treated Tlemcen as his eastern base. At that time the city had consisted of an older settlement called Agadir, but Ibn Tashfin founded a new city next to it called Takrart, which later merged with Agadir in the Almohad period to become the present city. The Almoravids subsequently clashed with the Hammadids to the east multiple times, but they did not make a sustained effort to conquer the central Maghrib and instead focused their efforts on other fronts. Eventually, in 1104, they signed a peace treaty with the Hammadids. Algiers became their easternmost outpost. Before campaigning in Al-Andalus, where the Taifas emirs were requesting his help, Ibn Tashfin made the capture of Ceuta his primary objective instead. Ceuta, controlled by Zenata forces under the command of Diya al-Dawla Yahya, was the last major city on the African side of the Strait of Gibraltar that still held out against him. In return for a promise to help him against the encroaching Christian kingdoms, Ibn Tashfin demanded that al-Mu'tamid ibn Abbad, the ruler of Seville, provide assistance in besieging the city. Al-Mu'tamid obliged and sent a fleet to