Anyone interested in the Viking Age should know about this hugely important edifice which has over the centuries served as both a physical border and an ideological one. The Dannevirke is a series of ditches and fortifications along the southern border of the Danish peninsula, effectively separating it from the rest of the continent. Archeological research estimates the first sections of the Dannevirke as having been build as early as the sixth century. Current scholarship theorizes that such fortifications were encouraged by constant conflict between the inhabitants of the peninsula and their southern germanic neighbors. In fact, this conflict is thought to have led to the exodus of Angles, Saxons, and Jutes to Britain. This first construct has more recently been identified as a possible shipping channel between the Baltic and the North Sea rather than a fortification (to read about the new discoveries, CLICK HERE).
Later evidence of further fortification begins in the early 9th century in the Royal Frankish Annals in which the Danish king Gudfred is said to have rebuilt the Dannevirke to repel Frankish invasion. Archeological finds place more extensive construction in the time of Harald Bluetooth, and scholars disagree over which monarch was most responsible for the expansion of the more extensive fortifications that earned the Dannevirke its later reputation as a symbol of the separation between the Danes and their southern Germanic neighbors.
During the Viking Age, the Danevirka was an important construct for the Danes of Jutland who felt the very real threat of invasion by the Frankish Empire. Although Charlemagne never materialized a full scale invasion, his son Louis the Pious sent frequent bellicose incursions toward Jutland, but never launched a frontal assault on the Danevirka. Luckily for the Danes, after the death of Charlemagne the Frankish Empire was plunged into repeated civil wars, taking the pressure off of their border and allowing them to begin their own foreign exploits in Normandy, Britain, and Brittany. In more simple terms, the Dannevirke prevented the invasion of Jutland by the Franks and allowed the Viking Age to have actually happened.
McKitterick, R. (2008). Charlemagne. Cambridge: Cambridge University Press.
Scholz, B. (1972). Carolingian chronicles: Royal Frankish annals and Nithard’s Histories. Ann Arbor: University of Michigan Press.