Excerpts from Books and Wikipedia
"The Song of Roland (French: La Chanson de Roland) is an 11th-century epic poem (chanson de geste) based on Roland and the Battle of Roncevaux Pass in 778, during the reign of Charlemagne. It is the oldest surviving major work of French literature and exists in various manuscript versions, which testify to its enormous and enduring popularity from the 12th to 16th centuries. . . . From a historical perspective, the Song of Roland's account of the Battle of Roncesvalles is questionable. According to Einhardt, writing in the late eighth century, (Life of Charlemagne) the antagonists are Basques who were incited to attack Charlemagne's army to avenge the looting of Pamplona." [Wikipedia]
"Stories were told about the minor ambush until it had been transformed into a pivotal battle; Roland became the hero of the first French epic, the twelfth-century Song of Roland, which turns the bloody incident into a major conspiracy between the Arabs of Zaragoza and a traitor within Charlemagne's own camp. . . But in reality, the Battle of Roncesvalles ended Charlemagne's ambitions in al-Andalus. He never pushed his way past the Pyrenees again." [Bauer: Medieval World, p. 378]