expeditions against Al-Andalus. Charlemagne decided to organize a regional subkingdom, the Spanish March, which included part of contemporary Catalonia, in order to keep the Aquitanians in check and to secure the southern border of the Carolingian Empire against Muslim incursions. In 781, his three-year-old son Louis was crowned king of Aquitaine, under the supervision of Charlemagne's trustee William of Gellone, and was nominally in charge of the incipient Spanish March. Meanwhile, the takeover of the southern fringes of Al-Andalus by Abd ar-Rahman I in 756 was opposed by Yusuf ibn Abd al-Rahman, autonomous governor (wāli) or king (malik) of al-Andalus. Abd ar-Rahman I expelled Yusuf from Cordova, but it took still decades for him to expand to the north-western Andalusian districts. He was also opposed externally by the Abbasids of Baghdad who failed in their attempts to overthrow him. In 778, Abd al-Rahman closed in on the Ebro valley. Regional lords saw the Umayyad emir at the gates and decided to enlist the nearby Christian Franks. According to Ali ibn al-Athir, a Kurdish historian of the 12th century, Charlemagne received the envoys of Sulayman al-Arabi, Husayn, and Abu Taur at the Diet of Paderborn in 777. These rulers of Zaragoza, Girona, Barcelona, and Huesca were enemies of Abd ar-Rahman I, and in return for Frankish military aid against him offered their homage and allegiance. Charlemagne, seeing an opportunity, agreed upon an expedition and crossed the Pyrenees in 778. Near the city of Zaragoza Charlemagne received the homage of Sulayman al-Arabi. However the city, under the leadership of Husayn, closed its gates and refused to submit. Unable to conquer the city by force, Charlemagne decided to retreat. On the way home the rearguard of the army was ambushed and destroyed by Basque forces at the Battle of Roncevaux Pass. The Song of Roland, a highly romanticized account of this battle, would later become one of the most famous of the Middle Ages. Around 788 Abd ar-Rahman I died and was succeeded by Hisham I. In 792 Hisham proclaimed a jihad, advancing in 793 against the Kingdom of Asturias and Carolingian Septimania (Gothia). They defeated William of Gellone, Count of Toulouse, in battle, but William led an expedition the following year across the eastern Pyrenees. Barcelona, a major city, became a potential target for the Franks in 797, as its governor Zeid rebelled against the Umayyad emir of Córdoba. An army of