Bruges to the islands on the west coast of Jutland. This region was progressively brought under Frankish control (Frisian-Frankish Wars but the Christianisation of the local population and cultural assimilation was a slow process. There is evidence that Frisians sometimes became Vikings themselves At the same time, several Frisian towns, most notably Dorestad were raided by Vikings. On Wieringen the Vikings most likely had a base of operations. Some Viking leaders took an active role in Frisian politics, such as Godfrid, Duke of Frisia. France The French region of Normandy takes its name from the Viking invaders who were called Normanni, which means ‘men of the North'. The first Viking raids began between 790 and 800 along the coasts of western France. They were carried out primarily in the summer, as the Vikings wintered in Scandinavia. Several coastal areas were lost to Francia during the reign of Louis the Pious (814–840). But the Vikings took advantage of the quarrels in the royal family caused after the death of Louis the Pious to settle their first colony in the south-west (Gascony) of the kingdom of Francia, which was more or less abandoned by the Frankish kings after their two defeats at Roncevaux. The incursions in caused severe damage to Rouen and Jumièges. The Viking attackers sought to capture the treasures stored at monasteries, easy prey given the monks' lack of defensive capacity. In an expedition up the Seine reached Paris. The presence of Carolingian deniers of , found in 1871 among a hoard at Mullaghboden, County Limerick, where coins were neither minted nor normally used in trade, probably represents booty from the raids of 843–846. However, from 885 to 886, Odo of Paris (Eudes de Paris) succeeded in defending Paris against Viking raiders. His military success allowed him to replace the Carolingians. In 911, a band of Viking warriors attempted to siege Chartres but was defeated by Robert I of France. Robert's victory later paved way for the baptism, and settlement in Normandy, of Viking leader Rollo. Rollo reached an agreement with Charles the Simple to sign the Treaty of Saint-Clair-sur-Epte, under which Charles gave Rouen and the area of present-day Upper Normandy to Rollo, establishing the Duchy of Normandy. In exchange, Rollo pledged vassalage to Charles in 940, agreed to be baptised, and vowed to guard the estuaries of the Seine from further Viking attacks. During Rollo's baptism Robert I