Contacts between the Carolingians and the Abbasids started soon after the establishment of the Abbasid Caliphate and the concommital fall of the Umayyad Caliphate in 751. The Carolingian ruler Pepin the Short had a powerful enough position in Europe to "make his alliance valuable to the Abbasid caliph of Baghdad, al-Mansur".[4] Former supporters of the Umayyad Caliphate were established firmly in southern Spain under Abd ar-Rahman I, and constituted a strategic threat both to the Carolingian on their southern border, and to the Abbasid at the western end of their dominion.