invaded the Duchy of the Pentapolis which had been given to the papacy in 756 by Charlemagne's father. Desiderius's support of the claims of Carloman's sons posed a potential challenge to the legitimacy of Charlemagne's possession of his brother's lands. In 773, he cut short a military campaign near Paderborn, crossed the Alps, and laid siege to Pavia. In exchange for their lives, the Lombards surrendered and Desiderius was sent to the abbey of Corbie. Charlemagne assumed the title "King of the Lombards". Franks From 781 Adrian began dating papal documents by the years of Charlemagne's reign, instead of the reign of the Byzantine Emperor. Friendly relations between pope and king were not disturbed by the theological dispute about the veneration of icons. In 787, Second Council of Nicaea, approved by Pope Adrian, had confirmed the practice and excommunicated the iconoclasts. Charlemagne, however, who had received the Council's decisions only in a bad Latin translation, consulted with his theologians and sent the Pope the Capitulare contra synodum (792), a response critical of several passages found in the council's acts. He also had his theologians, including Theodulf of Orleans, compose the more comprehensive Libri Carolini. Pope Adrian reacted to the Capitulare with a defense of the Council. In 794, a synod held at Frankfurt in 794 discussed the issue but refused to receive the Libri and contented itself with condemning extreme forms of veneration of icons. English In 787 Adrian elevated the English diocese of Lichfield to an archdiocese at the request of the English bishops and King Offa of Mercia to balance the ecclesiastic power in that land between Kent and Mercia. He gave the Lichfield bishop Hygeberht the pallium in 788. Muslim Spain Regarding the Muslims, he maintained the prohibition of Pope Zachary of selling slaves to Muslims, whom Adrian described as "the unspeakable race of Saracens," in order to guarantee a labor pool and to keep the power of Muslim rivals in check. He also encouraged Charlemagne to lead his troops into Spain against the Muslims there and was generally interested in expanding Christian influence and eliminating Muslim control. The rise in the number of Christian girls being married to Muslims in al-Andalus prompted a letter of concern from Hadrian. Hadrian's response was due to dispatches from bishop Egila who had been tasked with preaching the gospel in the peninsula. Egila eventually fell in with the Migetians, a