 Complete the following phrase:  By the 11th century mainland southern Italian powers were hiring Norman mercenaries, who were Christian descendants of the Vikings; it was the Normans under Roger de Hauteville, who became Roger I of Sicily, that captured Sicily from the Muslims. In 1038, a Byzantine army under George Maniaces crossed the strait of Messina, and included a corps of Normans. After another decisive victory in the summer of 1040, Maniaces halted his march to lay siege to Syracuse. Despite his conquest of the latter, Maniaces was removed from his position, and the subsequent Muslim counter-offensive reconquered all the cities captured by the Byzantines. The Norman Robert Guiscard, son of Tancred, then 