Berbers came in 712 under Ibn Nusayr himself. They supposedly helped the Umayyad caliph Abd ar-Rahman I in al-Andalus, because his mother was a Berber. English medievalist Roger Collins suggests that if the forces that invaded the Iberian peninsula were predominantly Berber, it is because there were insufficient Arab forces in Africa to maintain control of Africa and attack Iberia at the same time. Thus, although north Africa had only been conquered about a dozen years previously, the Arabs already employed forces of the defeated Berbers to carry out their next invasion. This would explain the predominance of Berbers over Arabs in the initial invasion. In addition, Collins argues that Berber social organization made it possible for the Arabs to recruit entire tribal units into their armies, making the defeated Berbers excellent military auxiliaries. The Berber forces in the invasion of Iberia came from Ifriqiya or as far away as Tripolitania. Governor As-Samh distributed land to the conquering forces, apparently by tribe, though it is difficult to determine from the few historical sources available. It was at this time that the positions of Arabs and Berbers were regularized across the Iberian peninsula. Berbers were positioned in many of the most mountainous regions of Spain, such as Granada, the Pyrenees, Cantabria, and Galicia. Collins suggests this may be because some Berbers were familiar with mountain terrain, whereas the Arabs were not. By the late 710s, there was a Berber governor in Leon or Gijon. When Pelagius revolted in Asturias, it was against a Berber governor. This revolt challenged As-Samh's plans to settle Berbers in the Galician and Cantabrian mountains, and by the middle of the eighth century it seems there was no more Berber presence in Galicia. The expulsion of the Berber garrisons from central Asturias, following the battle of Covadonga, contributed to the eventual formation of the independent Asturian kingdom. Many Berbers were settled in what were then the frontier lands near Toledo, Talavera, and Mérida, Mérida becoming a major Berber stronghold in the eighth century. The Berber garrison in Talavera would later be commanded by Amrus ibn Yusuf and was involved in military operations against rebels in Toledo in the late 700s and early 800s. Berbers were also initially settled in the eastern Pyrenees and Catalonia. They were not settled in the major cities of the south, and were generally kept in the frontier zones away from Cordoba. Roger