North Germanic peoples
Vikings were also active in Francia. Some of these Vikings would sail through the Strait of Gibraltar and pillage the coasts of the Mediterranean Sea. In the early 10th century, a group of Vikings under the leadership of Rollo settled in Rouen, France, and established the Duchy of Normandy. The descendants of these Vikings, known as the "Normans", would in the 11th century conquer England, Southern Italy, and North Africa, and play a leading role in launching the Crusades. Sub-groups of the Normans include Anglo-Normans, Scoto-Normans, Cambro-Normans, Hiberno-Normans and Italo-Normans.
Vikings
The motives driving the Viking expansion are a topic of much debate in Nordic history. One common theory posits that Charlemagne "used force and terror to Christianise all pagans", leading to baptism, conversion or execution, and as a result, Vikings and other pagans resisted and wanted revenge. Professor Rudolf Simek states that "it is not a coincidence if the early Viking activity occurred during the reign of Charlemagne". The penetration of Christianity into Scandinavia led to serious conflict dividing Norway for almost a century.