However, Einhard overstates Charlemagne's success. Frankish influence in Benevento proved to be very short-lived. In 788, both Grimoald's elder brother, Romuald, and Arechis himself died. Grimoald III, who was being held hostage by Charlemagne, succeeded as prince of Benevento. Unwisely, Charlemagne released Grimoald in return for an oath of loyalty. Grimoald did not keep his promise; by c. 791, he had effectively proclaimed himself independent and successfully resisted the Franks. Grimoald later tried to throw off Frankish suzerainty, but Charlemagne's sons, Pepin of Italy and Charles the Younger, forced him to submit in 792.