He and his elder brother Rotbold I were sons of Boson II of Arles and his wife Constance, who, based on her name, has been speculated to be daughter of Charles Constantine of Vienne.
At the Battle of Tourtour in 973, with the assistance of the counts of the High Alps and the viscounts of Marseille and Fos, he definitively routed the Saracens, chasing them forever from Provence.
With Isarn, Bishop of Grenoble, he repopulated Dauphiné and settled an Italian count named Ugo Blavia near Fréjus in 970 in order to bring that land back to cultivation.
For all this, he figures prominently in Ralph Glaber's chronicle with the title of dux and he appears in a charter of 992 as pater patriae.
His great principality began to diminish soon after his death as the castles of his vassals, which he had kept carefully under ducal control, soon became allods of their possessors.