On the death of Charles Martel in 741, his sons Pippin and Carloman assumed control, as mayors of the palace, of the territory of the Merovingian rulers of Frankish Gaul over which Charles Martel had established his authority. In 743 Carloman installed the last Merovingian king, Childeric III, on the throne, but Carloman himself relinquished secular power in 747 and departed for the monastery of Mount Soracte in Italy. In 751 Pippin usurped the Frankish throne for himself and became the first member of the Carolingian family to occupy it. It was Pippin's son Charlemagne who expanded the Frankish realms to embrace most of western Europe.
The Carolingian accounts of Pippin's takeover stress that Pippin III had the consent of his supporters and the approval, if not the actual authority, of the pope for his assumption of the Frankish throne. Thus Einhard in the first chapter of his Life of Charlemagne, written in about 817, comments (I use Paul Dutton's translation):
The family of the Merovingians, from which the Franks used to make their kings, is thought to have lasted down to King Childeric whom Pope Stephen ordered deposed. His long hair was shorn and he was forced into a monastery. Although it might seem that the [Merovingian] family ended with [Childeric III]it had in fact been without any vitality (vigor) for a long time and had demonstrated that there was not any worth in it except the empty (inanis) name of king. […]