Rostaing, a relative of Charlemagne, was appointed head of a vast county which also extended over the ancient pagi of Girona, Empúries and Besalú.
He called an assembly in Toulouse, attended by ambassadors of the King of Asturias, Alfonso II, and Bahlul Ibn Marzuq, a muwallad leader in revolt against Emir Al-Hakam I, who had seized Zaragoza.
On August 20, 800, a considerable army was gathered under the authority of the son of Charlemagne, Louis the Pious, named King of Aquitaine by his father in 781.
[3] The first, commanded by the count of Girona, Rostaing, led the siege, at the foot of the city; the second, led by the counts of Toulouse and Narbonne, William of Gellone and Adhemar, took position between the Muslim-held cities of Lleida and Zaragoza, to oppose the arrival of any Muslim relief troops from Cordoba; the third corps, commanded by Louis the Pious himself, was charged with protecting the Roussillon valley.
The Muslim wali of Barcelona, Sa'dun al Ruayni, seeing that the siege was going to last, left the city to ask for help from Cordoba, but he was discovered and captured by the Frankish troops, and then sent to the court of Aachen where he was condemned to exile.
The conquered territory however had several weak points, and a vulnerable border that made it poorly defended against possible Muslim attacks from the Upper March, reorganized around Zaragoza and its forward base of Lleida.