SCHOLARS and the contemporary accounts of the Carolingian annals agree that in the spring of 777, Sulaiman ibn al-Arabi, the pro-Abbasid ruler of Barcelona and Girona, traveled to Charlemagne's Diet of Paderborn in Westphalia in an effort to enlist the Frankish king's support in preserving the regional autonomy of Christian and Muslim rulers threatened by the increasing power of the amir of al-Andalus, Abd al-Rahman I. As a consequence of that visit, in the year 778, Charlemagne and his army of Franks entered Spain and laid siege to Zaragoza. The siege lasted a month; then, because of either Muslim intransigence or renewed Saxon hostilities in the north, the king gathered a multitude of hostages and turned his army and his attention to his northern frontier. On his passage through the Pyrenees, Charlemagne unleashed his wrath on Pamplona, destroying the Basque city and its walls. The Basques subsequently ambushed the rearguard of Charlemagne's army on the heights of the Pyrenees, killed numerous officers of the palace, plundered the baggage, and then vanished into the forested hills, leaving the Franks to grieve without the satisfaction of revenge.

Subsequent accounts soon provide more details, most prominently a biography of the emperor written by Einhard, a trusted friend of Charlemagne who based much of his account on personal experience. In his Vita Karoli Magni, the author describes how the Basques hid at the summit of the mountain, descended onto the baggage train as it traveled through a narrow passage, forced the troops who were at the very rear into an adjacent valley, and killed them to the last man. From among the dead he distinguishes Eggihard, overseer of the royal table, Anselm, palace count, and Roland, prefect of the frontier, as the most prominent. But the carefully constructed accounts of palace historians will have little influence over the subsequent renderings of Charlemagne's ill-fated incursion into Spain or of the battle that would later be identified with Roncesvalles, the valley where the princes of the Frankish rearguard were slaughtered.

We know that an oral narrative of Charlemagne's Spanish campaign traveled from France to Spain in due course, for there is a brief marginal gloss in a manuscript dated to the third quarter of the eleventh century that constitutes its first textual record.