A son of Billo, who was of Belluno, Pemmo moved to Friuli for political reasons and he ruled the Friulian duchy in the years of the Lombard age brightest splendour that coincided with Liutprand’s reign. He married Ratperga who gave him three children, two of whom, Ratchis and Aistulf, were kings of the Lombards. Pemmo has to be acknowledged the merit to put an end to the raids of Slavic populations that for more than a century had threatened the eastern border, which was just off the residence itself of the dukes, the city of Cividale. According to Paul the Deacon [Paolo Diacono], near Laurana Pemmo utterly defeated the Slavs and therefore undertook to get a peace treaty. The Historia Langobardorum recollects the duke as «homo ingeniosus et utilis patriae»: Pemmo looked after the orphans of the fallen in the battle against the Slavs and brought them up as if they were his own children. His name appears in the altar of Ratchis’ epigraph. Paul the Deacon [Paolo Diacono] gives prominence to the episode that induced king Liutprand to dismiss the brave duke of Cividale, around 735, after the death of patriarch Serenus. As a matter of fact Callistus [Callisto], the new metropolitan of Aquileia, dissatisfied with residing, as his predecessors, in the ‘castrum’ of Cormòns, expelled Amator, the bishop of ‘Iulium Carnicum’ (Zuglio), and took over his residence in the palace of Cividale where the bishops of the Carnic diocese had been obliged to settle due to the threat of Slavs and Avars. Pemmo’s reaction was not to be long awaited: after arresting Callistus [Callisto], he took him prisoner to the castle of ‘Potium’ (Duino) and threatened to throw him into the sea, but then he kept him in gaol. Following that Liutprand, a very religious man, took up the part of the metropolitan and, after deposing the duke, he replaced him with his son Ratchis. Pemmone took refuge among the Slavs and Ratchis asked the king to forgive his father. It is still obscure whether the king consented his forgiveness to Pemmo: however Callistus [Callisto] definitely settled in Cividale. After this event, one of the most important and more fraught with consequences for the religious and political history of the medieval Friuli, the city became the residence of the patriarchs.
For further information see the entry Pemmone, duca del Friuli written by Massimo Dissaderi in Nuovo Liruti. Dizionario biografico dei Friulani, 1, Il Medioevo, edited by C. Scalon, Udine, Forum, 2006, 676-678.