After his brother Ratchis became king, Aistulf succeeded him in Friuli. He succeeded him later as king when Ratchis abdicated to a monastery. Aistulf continued the policy of expansion and raids against the papacy and the Eastern Roman exarchate of Ravenna. In 751, he captured Ravenna itself and even threatened Rome, claiming a capitation tax. He also conquered the Istria region from Eastern Roman occupation in the same year.
The popes, thoroughly irritated and alarmed, and despairing of aid from the Roman Emperor, turned to the Carolingian mayors of the palace of Austrasia, the effective rulers of the Frankish kingdom. In 741, Pope Gregory III asked Charles Martel to intervene, but he was too busy elsewhere and declined. In 753, Pope Stephen II visited Charles Martel's son Pepin the Short, who had been proclaimed king of the Franks in 751 with the consent of Pope Zachary. In gratitude for the papal consent to his coronation, Pepin crossed the Alps, defeated Aistulf, and gave to the pope the lands which Aistulf had torn from the ducatus Romanus and the exarchate (Emilia-Romagna and the Pentapolis).
Aistulf died hunting in 756. He was succeeded by Desiderius as king of the Lombards and by Alboin as duke of Spoleto. He had given Friuli to his brother-in-law Anselm, abbot of Nonantula, whose sister Gisaltruda he had married, when he succeeded to the kingship in 749.
- Lars Ulwencreutz (November 2013). Ulwencreutz's The Royal Families in Europe V. Lulu.com. p. 350–. ISBN 978-1-304-58135-8.
- Thomas Hodgkin (1899). Italy and Her Invaders: Frankish invasions, 744-744. Clarendon Press. p. 164.
- "German Tribes org Lombard Kings". GermanTribes.org. Archived from the original on 2010-07-18. Retrieved 2010-07-18.