The Lombards to the north of Rome had captured Ravenna, former capital of the Byzantine Empire exarchate, in 751, and began to put pressure on Rome. Relations were very strained in the mid-8th century between the papacy and the Byzantine emperors of the Isaurian dynasty, and no help came from Constantinople. Stephen turned to Pepin the short, Mayor of the Palace of the Kingdom of the Franks. Pepin took the opportunity to ask Stephen the question "who should be king of the Franks, the one with the title or the one with the power." Stephen agreed that the one with the power should be King of the Franks. Pepin deposed Childebert III and the Franks chose Pepin as King.
Pepin invaded Italy twice to settle the Lombard problem, delivered the territory between Rome and Ravenna to the papacy, but left the Lombard kings in possession of their kingdom.