Ibn Yasin now formed the Al-Murabitoon alliance from the tribes of the Lamtuna, the Masufa and the Judala, with himself as spiritual leader and Yahya ibn Umar taking the military command. In 1054 the Maghrawa-ruled Sijilmasa was conquered. Ibn Yasa introduced his orthodox rule - amongst other things wine and music were forbidden, non-islamic taxes were abolished and one fifth of the spoils of war were allocated to the religious experts. This rigorous application of Islam soon provoked a revolt in 1055.
Yahya ibn Umar was killed in 1056 in a renewed revolt of the Judala in the Sahara, upon which Ibn Yasin appointed Yahyas brother Abu-Bakr Ibn-Umar (1056-1087) the new military leader. Abu Bakr destroyed Sijilmasa, but was not able to force the Judala back into the Al-Murabitoon league. He went on to capture Sūs and its capital Aghmat (close to where is now Marrakech) in 1057.
Ibn Yasin died while attempted to subjugate the Bargawata on the Atlantic coast in 1059. His grave is 33 km almost due south of Rabat, overlooking the Korifla River, marked on Michelin maps as the marabout of Sidi Abdallah.