The Muslim community in the Iberian Peninsula was itself diverse and beset by social tensions. The Berber people of North Africa, who had provided the bulk of the invading armies, clashed with the Arab leadership from the Middle East. Over time, large Moorish populations became established, especially in the Guadalquivir River valley, the coastal plain of Valencia, the Ebro River valley and (towards the end of this period) in the mountainous region of Granada.