In the spring of 778 (late March or early April), after stationing garrisons at selected points along the border with Saxony, Charlemagne launched a military expedition composed of two legions or about 20,000 men to seize the Muslim cities and occupy Pamplona. The chroniclers recount that the king crossed the Pyrenees with the greatest display of military might available, causing all of Hispania to tremble at the sight of his vast legions.
This army included Franks and mercenaries from nearly all the peoples subdued by the emperor: Bavarians, Lombards, Burgundians, Septimanians, and even Muslims (et coniugentes), which required a considerable administrative and economic effort. The sources note that neither Aquitanians nor Basques were among the king’s troops, as this campaign was specifically aimed at pillaging Pamplona and the broader Vasconia in the Iberian Peninsula.
The army advanced in two columns, each crossing potentially hostile territory and hence each comprising at least one legion or 10,000 men. Charlemagne personally led the main force toward Pamplona from the west via the Zize pass, also known as Errozabal (Roncesvalles), commanding the Neustrian troops. A second army, consisting of troops from Austrasia, Burgundy, Lombardy, and Provence, crossed the eastern Pyrenees through the Pertus pass, entering Girona and Barcelona, and would rendezvous with the king’s forces in Zaragoza.
When the expedition led by the king reached Cassinogilum (Aquitania), it paused at the border with Vasconia to celebrate Easter, which that year fell on Sunday, April 14. After celebrating Easter in Cassinogilum, Charlemagne left his pregnant wife Hildegard there. He wished for his son and future king to be born in Aquitaine, which would grant him the authority needed to lead the Aquitanians and Basques in the future. On April 16, a Tuesday, Hildegard gave birth to twins, Lothar and Clovis, the latter known later as Louis the Pious (Ludovicus Pius).
To penetrate the Basque Pyrenees, the Frankish troops had to cross the Garonne and navigate through hostile Vasconia, covering 600 km from Cassinogilum to Pamplona. The king ensured the neutrality of the Basque princeps, Otsoa Lupus II, through a pact and by taking hostages, including members of his family.
After a journey of approximately 1,200 kilometers from Douzy to Pamplona, which took about three months, Charlemagne’s army reached the gates of Pamplona in early June 778. They arrived before the harvest of the surrounding fields, planning to starve the city into submission to ensure the success of the siege, and if necessary, to take provisions for the troops’ sustenance.
The sources provide no detailed account of the Battle of Pamplona but specify that the king captured the city by force.
