In August 778, Charlemagne led his Frankish army back from Spain through the Pyrenees. His campaigns in Saxony had expanded the Frankish Kingdom, integrating Saxons and battling paganism. Seeking to extend his empire, he allied with Muslim governors opposing the Umayyad emir of Cordoba. Despite initial successes in Iberia, Zaragoza's gates closed against him, leading to a siege. The situation worsened when his rearguard was ambushed at Roncevaux Pass, marking a pivotal moment in his campaign.