y 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.
Córdoba, the capital of the caliphate, was the largest, richest and most sophisticated city in western Europe. Mediterranean trade and cultural exchange flourished. Muslims imported a rich intellectual tradition from the Middle East and North Africa. Muslim and Jewish scholars played an important part in reviving and expanding classical Greek learning in Western Europe. The Romanised cultures of the Iberian peninsula interacted with Muslim and Jewish cultures in complex ways, thus giving the region a distinctive culture. Outside the cities, where the vast majority lived, the land ownership system from Roman times remained largely intact as Muslim leaders rarely dispossessed landowners, and the introduction of new crops and techniques led to an expansion of agriculture.
In the 11th century, the Muslim holdings fractured into rival Taifa kingdoms, allowing the small Christian states the opportunity to greatly enlarge their territories. The arrival from North Africa of the Islamic ruling sects of the Almoravids and the Almohads restored unity upon the Muslim holdings, with a stricter, less tolerant application of Islam, and saw a revival in Muslim fortunes. This re-united Islamic state, experienced more than a century of successes that partially reversed Christian gains.
Fall of Muslim rule and unification
The Reconquista ("Reconquest") was the centuries-long period of expansion of Iberia's Christian kingdoms. The Reconquista is viewed as beginning with the Battle of Covadonga in 722, and was