The conquest which brought about the demise of the taifas of the Ebro region and the expulsion of the Almoravids and the Almohads represented one of several stages of contact between the Christian principalities of the Pyrenees and their Muslim neighbors. In the period of the Caliphate the role of the kings of Pamplona (whose dominion extended east towards Urgell until the foundation of Aragon) and the Catalan counts was that of tributaries, but by the late eleventh century the balance of power had swung in their favor and it was they who were able to demand parias from the Muslim rulers of what had been the Furthest March. Although political hegemony in these centuries can be characterized to a certain extent according to religious identity, both Muslim and Christian power were actually fragmentary, manifested by competing entities which vied for supremacy amongst coreligionists as much as against confessional rivals.

The first sections of this chapter examine cross-frontier contact which arose as a consequence of the implication of Christians and Muslims in each others' political struggles, contrasting accommodating trends with the hostile ideologies of Holy War which developed in this same era. The last three sections focus on developments within the Christian kingdom of Aragon and the Catalan counties under the domination of Barcelona. The circumstances of the early conquest of the Ebro region under Alfonso I of Aragon and its consolidation in the late twelfth century were decisive in determining the character of mudéjar society in the Crown of Aragon.