After 911, the Viking Rollo was the first Norman count of Rouen. His successors were called Dukes of Normandy. These dukes increased the strength of Normandy, although they had to observe the superiority of the king of France. They held on to some territory in Scandinavia and the right to enter those lands by sea. The aristocracy was composed of a small group of Scandinavian men, while the majority of the Norman political leaders were of Frankish descent.