New Research Indicates That King Harald Bluetooth Built Fortresses To Protect Himself From Other Vikings

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A Danish fortress, Borgring, along with several others were built by the famous Viking King Harald Bluetooth. However, new research indicates that Bluetooth built these fortifications to protect himself from other Vikings.

Archaeologist Søren M. Sindbæk and his colleague, Nanna Holm, from the Museum Southeast Denmark have spent the last four years researching the Borgring fortress in Lellinge, Denmark. Now, after all this time, they have come to the conclusion that King Harald Bluetooth was building forts in Denmark to protect himself from other Vikings and not from the Germans, as first suspected.

Considered the second king of Denmark, Bluetooth ruled circa 958 and 987 CE. Among other things, Bluetooth is considered to have brought Christianity to Denmark. Although, this fact is hotly contested by scholars due to conflicting accounts from the time.

During his reign, he was knocked back by the Germans in 974. There was the assumption that the forts built by Harald Bluetooth were as a result of this conflict. However, many of these fortifications, such as the Borgring fortress, were built a long distance away from the Danish-German borders. In addition, he had other fortresses placed on the islands of Fyn and Zealand, and Skane in southern Sweden.

According to the new research, published in Science Nordic, Sindbæk puts forth the theory that these fortresses were erected to protect Bluetooth from other Vikings, rather than the Germans.

The Viking king, Harald Bluetooth built several ring fortresses across Denmark
Featured image credit: National Museum of Denmark

Initially, researchers thought Bluetooth was building fortresses as a line of defense from King Otto I. It is also suspected that Otto was the reason Bluetooth converted to Christianity in order to avoid the German king’s tyranny. Otto I was replaced by his son, Otto II, in 973. And, it is Bluetooth’s conflict with Otto II that ties in with the construction of the fortresses.

Now, Sindbæk suggests that King Harald Bluetooth built his fortresses so far away from Germany because he was defending his lands from both sides. In other words, while Bluetooth was distracted by the German conflicts to the south, others were taking advantage of his lack of defenses on the other side. Most notably, this would be Norway and Sweden.

So, in effect, it seemed that Harald Bluetooth was protecting his kingdom from attacks from other Vikings.

These fortresses were considered Harald’s coastal defense.

“Rather than being Viking fortresses, they were actually ‘anti-Viking’ fortresses,” Sindbæk explains in his research.

Along with the Borgring fortress, King Harald Bluetooth is also credited with building the Trelleborg, Fyrkat, Nonnebakken, and Aggersborg fortresses in Denmark, as well as Borgeby in southern Sweden.