Adrian or Hadrian I, Pope 772-795, was the son of Theodore, a Roman nobleman.
In 773 Adrian appealed to Charlemagne for help against the Lombards; in response (and for his own reasons) Charlemagne besieged Pavia and ended the rule of Desiderius, keeping the Kingdom of the Lombards for himself and extending Frankish control to the northern part of the Italian peninsula.
Adrian was not a puppet of the Carolingians, however. When the Second Council of Nicaea forwarded their proclamation on Iconoclasm and the restoration of images in the Byzantine Empire, Adrian accepted the pronouncement despite Frankish opposition.
Text from 1911 encyclopedia
ADRIAN I., pope from 772 to 705, was the son of Theodore, a Roman nobleman. Soon after his accession the territory that had been bestowed on the popes by Pepin the short was invaded by Desiderius, king of the Lombards, and Adrian found it necessary to invoke the aid of Charlemagne, who entered Italy with a large army, besieged Desiderius in his capital of Pavia, took that town, banished the Lombard king to Corbie in France and united the Lombard kingdom with the other Frankish possessions. The pope, whose expectations had been aroused, had to content himself with some additions to the duchy of Rome, and to the Exarchate, and the Pentapolis. In his contest with the Greek empire and the Lombard princes of Benevento, Adrian remained faithful to the Frankish alliance, and the friendly relations between pope and emperor were not disturbed by the difference which arose between them on the question of the worship of images, to which Charlemagne and the Gallican Church were strongly opposed, while Adrian favoured the views of the Eastern Church, and approved the decree of the council of Nicaea (787), confirming the practice and excommunicating the iconoclasts. It was in connexion with this controversy that Charlemagne wrote the so-called Libri Carolini, to which Adrian replied by letter, anathematizing all who refused to worship the images of Christ, or the Virgin, or saints. Notwithstanding this, a synod, held at Frankfort in 794, anew condemned the practice, and the dispute remained unsettled at Adrian's death. An epitaph written by Charlemagne in verse, in which he styles Adrian "father," is still to be seen at the door of the Vatican basilica. Adrian restored the ancient aqueducts of Rome, and governed his little state with a firm and skilful hand.