Rollo the Viking was granted land in Northwestern France in 911 AD by Charles the Simple, King of France. Charles hoped that Rollo would defend his new land, barring the length of the Seine River to other Viking groups. Rollo remained faithful to Charles and he and his son quickly expanded the original land grant at the expense of neighboring French lords and guarded it well against Viking rivals. Even before Rollo's grandson Richard took over the domain in 942, the descendants of the Vikings had accepted Christianity, intermarried with the local population and adopted the French language. Already they were being called Normans, a contraction of Northmen, and there territory became known as Normandy. Richard's great-grandson was King William I, conqueror of England. Rollo was also known as "Rolf."