His installation was meant to protect the eastern border of the Frankish realm against the threatening Wends under Samo, who had defeated the king at the 631 Battle of Wogastisburg and formed an alliance with Dervan, prince of the Sorbian tribes settling in the adjacent region east of the Saale river. Radulf fought successfully against the Slavs, but subsequently refused the incorporation of the secured territories into the Austrasian kingdom. To retain his independence he allied with Fara, a descendant of the powerful Agilolfing dynasty in Bavaria who ruled over large estates along the Main river.