 In the 4th century, Gratian divided the province into the civitates that constitute the historical borders.After the fall of Rome in the 5th century, the Franks became the dominant ethnic group in the area, built several monasteries, and replaced the barbarism of the region with the civilization of the Carolingian Empire.Towards the end of the 8th century, Viking raids devastated the region, prompting the establishment of the Duchy of Normandy in 911.