The Norman settlement of northern France began in an era of extensive raids by various Norse tribes along the coast and rivers which were easily accessible by ship. The first recorded Norse raid along the Seine was in 820, after which small settlements were established in the area. Norman territory was officially recognized in the treaty of Saint-Clair-sur-Epte in 911, in which the Viking leader Rollo was granted lands by the Frankish king, Charles III. In return for the territory, Rollo pledged his allegiance to Charles and agreed to defend France against further Norse attacks. After Charles III was deposed in 923, the newly elected King Rudolph of western Francia granted the Normans further territory, and again in 933 when Rollo’s son William Longsword pledged allegiance to Rudolph, who was now engaged in a power struggle. From this point the Normans consolidated their power and adopted Catholicism along with other Frankish customs.