The year was 778. Charlemagne, starting homeward after an expedition onto the Iberian Peninsula, left his nephew, Count Roland, in command of a rear guard. As Roland and his troops moved through the Pyrenees, a fierce enemy swooped down and annihilated them. Whether the attackers were Moors, Basques, Gascons, or Aquitainians is still disputed. The massacre soon passed into legend, preserved but at the same time expanded and interpreted in oral tradition and written accounts.

Dormant after the late Middle Ages, the legend began to inspire literary works even before the discovery and...