[1] According to ibn al-Athir, threatened by Abd ar-Rahman I, the Umayyad emir of Córdoba, al-Arabi sent a delegation to Charlemagne at the diet in Paderborn, offering his submission, together with the allegiance of Husayn of Zaragoza and Abu Taur of Huesca in return for military aid.
As a result, Charlemagne marched across the Pyrenees toward Zaragoza in 778, joined by troops led by Sulayman.
After a month of siege Charlemagne decided to return to his kingdom, taking some hostages from his Muslim allies including Sulayman.
However, on his retreat north his baggage train was ambushed at the battle of Roncevaux Pass August 15, 778.
[3] These historical events are assumed to be part of the factual nucleus around which was eventually formed, by centuries of oral tradition on the Christian side, the Song of Roland, which was to have an immense importance in the medieval culture of France and the whole of Christian Western Europe.