A very interesting article from ScienceNordic on archaeologists from Aarhus University, Denmark, and their continuing work on the country's Viking Ring Fortresses, constructed at the direction of King Harald Bluetooth during his reign in the 10th century. (Ed. )
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August 21, 2018 -
06:25
After four years,
the excavation of the famous Viking fortress, Borgring, is coming to a close
and archaeologists can now describe the fortress in a broader perspective: An
anti-Viking defence that allowed the Danish King to forge a new, mobile army.
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Trelleborg is one of the five Viking fortresses in Denmark, built by Harold Bluetooth at the end of the 900s CE. (Photo: National Museum of Denmark) |
The news travelled
around the world, and since then our excavations have continued to cast new
light on the Viking Age.
Thousands of
visitors have flocked to the site, which has been open each summer as a living
museum. But if you want to visit then you will need to be quick, as this summer
will probably be the last year of excavations at Borgring.
Here are some of
the most important and surprising discoveries made during the excavations.
These finds not only tell us about the history of the fortress, but also about
the purpose of these unique, ring fortresses.
A “new” ring
fortress?
Borgring is one of
five, large ring fortresses from the Viking Age in Denmark. Each of the large
fortresses were constructed in a perfect circle and are some of the best known
monuments left by the Vikings.
The other
fortresses include Trelleborg, Fyrkat, Nonnebakken, and Aggersborg, as well as
Borgeby in Southern Sweden. All were built by King Harold Bluetooth who reigned
between circa 958 and 987 CE and is best known in Denmark for erecting
the Jelling Stone—a large stone with the first written
reference to the name “Denmark,” often referred to as Denmark’s birth certificate.
It had been 60
years since archaeologists had discovered such a ring fortress in Denmark when
we finally found Borgring. Many doubted that it was indeed a Viking fortress,
while others claimed that the fortress had been known about for some time.
Locals remember an
officer from the Danish Air force spotting the outline of the fortress in 1970,
in aerial photos. He contacted the National Museum of Denmark who investigated
the site and concluded that there were no Viking remains. People thus knew about
the old earthworks in a field north of Lellinge, but archaeologists did not
connect it to Harold Bluetooth’s fortresses.
Discoveries started
to turn up
But the critics
came around, as the results of the excavations started coming in.
Among the most
important results, which ScienceNordic has previously written about, are.
Carbon-14 dating,
which placed the fortress in the early 900s.
In May 2018, Aarhus
University together with the Danish Agency for Culture and Palaces, held a
conference on the Danish Viking Age ring fortresses, which are to be nominated
as UNESCO world heritage sites. It was clear that even the researchers who had
been sceptical, were no longer in any doubt that Borgring was one of Harold
Bluetooth’s fortresses.
A network of
fortresses
Since 2016,
scientists from Museum Southeast Denmark, the National Museum of Denmark, and
Aarhus University, Denmark, have excavated the site, with funding from the A.P.
Møller Foundation and Køge Municipality.
We’ve learnt a lot
about the fortress’s history, but also about the Viking fortresses in general.
The fortresses are
impressive enough on their own. But the most unique aspect is that they were
constructed as a coordinated project—a network of fortresses across the
country.
 |
| Ring fortresses (dark blue circles) and other focal points of Harold Bluetooth’s kingdom. The shading indicates proximity to medieval churches (red = dense), which gives an indication of the population density shortly after the Viking Age. Roads (white lines) represent the old network, many of which have existed since the Viking Age. (Graphic: Søren M. Sindbæk/Aarhus University) |
Many have tried to
explain what purpose the network of fortifications served. Here, it’s important
to ask the right questions, as the challenge is to find an explanation that
best accounts for everything that we know about these fortresses.
Big fortifications,
short lifespan
The 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 Hedeby (in modern day Germany), Ribe, and
Aarhus.
Chieftains and
kings built large halls and farms, but not fortresses.
Four hypotheses for
the Viking fortresses
Why did Harold
Bluetooth build five fortresses in the 970s?
This is the central
question that has bothered Viking researchers since the fortresses were first
discovered. So far, four main hypotheses have been floated:
Training camps for
the Viking army that conquered England around the time of Sweyn Forkbeard. 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.
Fortified centres
of royal control built by Harold Bluetooth to subdue the population in the
newly united Denmark: 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?
Military bases
during the fight between Bluetooth and his son, Sweyn Forkbeard: Bluetooth’s
son rebelled against his father, but 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.
A result of an
extraordinary foreign policy situation: Early in Bluetooth’s reign, a new power
was growing from central Europe under King Otto I, who was 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. Let me explain why.
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), upping 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?
In 2014 I put forward
another version of this “invasion theory,” together with my colleague Else
Roesdahl. We suggested that the acute danger probably came from Otto II, which
explained the timing of the fortress construction.
But another factor
can explain the distribution of fortresses around the country: The threat from
the south left Harold Bluetooth exposed to other threats from elsewhere,
specifically 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.
A new theory
 |
| Archaeologist Nanna Holm excavates burnt posts at Borgring’s east gate. The charred wooden posts give a clear indication of the fortress construction. (Photo: Søren M. Sindbæk/Aarhus University) |
It was this
hypothesis that led us to discover Borgring.
It suggested that
Harold Bluetooth must also have had a fortress to protect the east coast of the
country, which turned out to be the case.
What we couldn’t
explain was, how exactly the fortresses were used as a defence. And this is
where the discoveries made at Borgring can shed some new light.
With this in mind,
we can propose a new explanation for the fortresses, and a more direct
connection between Harold Bluetooth’s fight on the southern borders and his
need for coastal defences in the rest of the country.
Built in a hurry
The excavations at
Borgring have revealed a fortress built to the same design as Trelleborg and
the other ring fortresses. We also see that the fortifications were well
planned and completed swiftly.
The landscape was
levelled, and the walls were built in a precise circle, with gently sloping
sides inside the fortress. The interior is divided into even sections, with
four wooden gates placed at exactly 90 degrees to each other.
But then… nothing.
There’s no sign of
repairs or extensions to the walls, there are only feeble traces of wooden
constructions, which could have supported a high wall, and unlike Trelleborg,
Fyrkat, and Aggersborg, there are no signs of construction in the interior of
the fortress.
But there are
traces of a damaging fire in numerous places around the fortress, and deep
wheel tracks that suggest long-term use by traffic coming in and out.
A fortress for
refugees
How can we explain
these features? It is possible that the construction was interrupted
prematurely, but in this case we might have expected to see more clear traces of
the building process, and we wouldn’t expect to see any later activity.
The wheel tracks
suggest that Borgring was sufficiently ready for use, even without the
construction of actual buildings or dwellings inside.
Looking at the
excavation drawings from Trelleborg made in the 1930s, we see that the fortress
walls were built up numerous times, with the oldest phase most similar to the
walls at Borgring.
And Borgring is not
alone: One of the other fortresses, Nonnebakken, does not appear to have any
interior buildings either. This suggests, that the primary function of the
fortresses was not to house a permanent settlement, but to allow people to flee
there for short periods of time.
This function as a
place for refugees to seek shelter, points to a new and stronger connection
between the fortresses and Harold Bluetooth’s was against Otto II.
Fortresses sent
warriors to the southern border
Fire experts from the Danish police fire department assist Søren Sindbæk (right) during the excavation of the burnt gates. (Photo: Søren M. Sindbæk/Aarhus University)
The war with the
south meant that Harold needed to call up reinforcements from all of the
supporting chieftains to gather warriors along the southern border.
Such an operation
was described in the Skaldic poem Vellakla, written as a praise poem to the
Norwegian Earl Hakon, a contemporary of Harald Bluetooth. According to the
poem, Hakon was summoned to assist Harald’s fighting at the Danevirke.
This left over
parts of the country without the warriors who would usually defend them and
entirely unprotected. In order to win the war with the south, Bluetooth had to
offer some other form of protection to these areas, hence the fortresses.
Placed on top of a
fortified wall, it was possible for a poorly armed and untrained person, man or
woman, to fight off a well-trained warrior.
If enough people
sought refuge in the fortress, then the attackers were unlikely to take it.
They could initiate a siege, but time would be against them.
A successful
strategy
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 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.
Harold Bluetooth
strengthened his power base
Constructing the
ring fortresses, allowed Harold to consolidate his power throughout the kingdom
in a way that no other king of Denmark had done before.
The large buildings
of Trelleborg suggest that some of the fortresses came in due time to take on a
more active role as settlements or perhaps winter camps for warriors. But first
and foremost, this network of fortresses allowed the king to exploit his chief
military assets, warriors, more effectively.
These warriors did
not man the fortresses, which were, on the contrary, a means of protecting the
portion of the population who were not warriors. This was a decisive
countermeasure that allowed Harold to defend and win the war in another part of
the kingdom.
Excavations at
Borgring have revealed new pieces of the puzzle to understand all of Harold
Bluetooth’s fortresses.
You can still catch
a glimpse of the excavations of the walls and west gate, before this little
piece of Viking Age Denmark will be covered by soil and grass once more.
Translated by
Catherine Jex
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