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Viking Fortresses by Rob Shackleford

Viking Fortresses by Rob Shackleford

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Who Were the Vikings?

What did Vikings Look Like?

Viking Ginger Connection

Vikings Dirty and Unkempt

Viking Hygiene

Viking Clothes – Looking Good!

Viking Men’s wear

Viking Women’s Wear

Vikings Loved Bling Part 1

Viking Jewellery Part 2

Inked Up – Vikings and Tattoos

Were Vikings Inked?  Part 2

Viking Health

Viking Teeth

Viking Medicine

Vikings at Home Viking Society Viking Thralls Viking Karls
Viking Jarls Viking Women Part 1 Viking Women Part 2 Viking Women Part 3 Viking Villages and Towns

Viking fortresses by Rob Shackleford


This may come as a surprise, but Vikings generally didn’t create fortresses. Some settlements might have included walls, while chieftains and kings built large halls and farms, but not fortresses.

In this blog I will rely heavily on the notes from Danish archaeologists who have been working on recent discoveries of Viking fortresses. Notes by Søren M. Sindbæk, Professor of archaeology, Aarhus University, Denmark, are relied on to make sure my facts are accurate.

It seems that Viking ring fortresses only existed for a short part of the Viking Age.

Two of the best dated fortresses, Fyrkat and Trelleborg, look to have been established between 974 and 981, and finds from the other fortresses suggest a similar date.

No other large fortifications existed in Denmark in the rest of the Viking Age, from the end of the 700s up to 1000s, except for city walls in the Viking town of Hedeby (in modern day Germany), Ribe, and Aarhus.

A reconstruction of the Viking town Hedeby in Viking Fortresses by Rob Shackleford
A reconstruction of the Viking town of Hedeby in modern Germany

Why Viking fortresses?

Viking fortresses were built under the rule of Viking King Harald Bluetooth.

Because documented history for the Vikings is either scant or reliant on the observations of others, many issues in Viking life can only be solved with archaeology.

So far, archaeologists have four main hypotheses for the creation of these forts:

  1. The fortresses were training camps for the Viking army that conquered England around the time of his son, Sweyn Forkbeard’s reign.

This hypothesis was shelved in the 80s, when tree-ring dating revealed that Trelleborg and Fyrkat fortresses were built and used decades before the large attack on England.

  1. Fortified centres of royal control were built by Harold Bluetooth to subdue the population in the newly united Denmark:

Viking fortresses by Rob Shackleford

This was the dominant hypothesis for many years, but the dates again did not fit. Why would Bluetooth build the fortresses in the later part of his reign, long after he became king around 958 CE, and long after he declared Denmark a Christian country in 963 CE?

  1. The Viking fortresses were military bases during the fight between Bluetooth and his son, Sweyn Forkbeard. Bluetooth’s son rebelled against his father.

If the fortresses were built around 975, this rebellion must have lasted more than a decade across the entire country. Again, it didn’t fit.

  1. Perhaps the fortresses were a result of an extraordinary foreign policy situation. Early in Bluetooth’s reign, a new power was growing from central Europe under the great German King and eventually Holy Roman Emperor – King Otto I, crowned emperor in 962. Otto’s growing power was probably a crucial factor in Harold Bluetooth’s conversion to Christianity, to avoid becoming Otto’s next target. Many researchers have come to the conclusion, that it was the unique set of challenges posed by this situation that led Harold Bluetooth to construct the fortresses.

It is suggested that the fortresses were really a network to defend against Viking attacks

Otto I died in 973 and was succeeded by his son, Otto II who attacked Danevirke (in what is modern day Germany), increasing the threat to Harold Bluetooth’s Denmark, which remained a target for war until Otto II’s death in 983.

These events coincide precisely with activity at the fortresses, and can explain the need for such unusual fortifications.

But a mystery remains: If the threat was from Germany, why were they built so far from the Danish-German border, on the island of Fyn and Zealand, and Skåne in southern Sweden?

Another factor that can explain the distribution of fortresses around the country is because the threat from the south left Harold Bluetooth exposed to other threats from elsewhere, specifically from other Vikings from Norway and Sweden, who might try to exploit the king’s weak position.

And so fortresses were established right across the kingdom. They was a coastal defence: Rather than being Viking fortresses, they were actually “anti-Viking” fortresses.

The fortresses offered protection to locals, in the absence of the warriors who had be called up to protect the south. This allowed locals to withstand fellow-Viking attacks and provided Harold Bluetooth with a mobile army that he could deploy to the German border.

The fortresses were intended to deter potential attackers, by allowing the local population to seek shelter and defend themselves.

Seen this way, the fortresses are no longer a mystery. In fact, they successfully fulfilled their mission.

Viking fortresses by Rob Shackleford


About the author:

Hi, I’m Rob Shackleford. I am author of a number of novels, though so far only Traveller Inceptio and Traveller Probo have been officially published. As Traveller Inceptio looks at the fates of modern historical researchers sent to the early 11th Century Saxon world, Vikings do feature.

Below are the Amazon links for the two novels so far.

In reading my novels, I ask if you wouldn’t mind posting a review and, perhaps, a picture of yourself with my book – either paperback or on kindle. Link to me on Social Media. I most welcome your comments and images.

I hope you enjoy.

Rob Shackleford Traveller Inceptio - a novel by Rob Shackleford Traveller Probo - Book 2 of the Traveller Series by author Rob Shackleford

Check out my web site at

In my vain attempt to attract attention and promote my books – please check out my brief skit video:

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Rob Shackleford - The Coin short story

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