Sachsenkriege Karls des Großen
The Vikings witnessed the violent subduing of the Saxons by Charlemagne, in the thirty-year Saxon Wars of 772–804. The Saxon defeat resulted in their forced christening and the absorption of Old Saxony into the Carolingian Empire. Fear of the Franks led the Vikings to further expand Danevirke, and the defence constructions remained in use throughout the Viking Age and even up until 1864.