He was the son of Tancred de Hauteville, and with his brother Roger established himself in southern Italy. In 1053 they defeated the forces of Pope Leo IX, securing Apulia and Calabria. Pope Nicholas II, enlisting Norman aid against the Byzantines, gave him Sicily, though it was not finally conquered till 1090. Excommunicated by Pope Gregory VII for his attack on Benevento, he nevertheless fought for him against the invading Henry IV of Germany. The brothers sacked Rome in 1084, driving Henry out.