 That year, King Raoul of France was forced to give Cotentin and a part of Avranchin to William I of Normandy, essentially all lands north of the Sélune River which the Breton dukes had theoretically controlled for about the previous 70 years.Between 1009 and 1020, the Normans continued their westward expansion, taking all the land between the Sélune and Couesnon rivers, including Mont Saint-Michel, and completing the conquest of Avranchin.William the Conqueror completed these campaigns in 1050 by taking Passais.