The Viking Forts
by Sir Egil Njalsson
(December 1995)

(Note to the reader: a set of photos, yet to be scanned, accompanies this article.)

The tenth century was a time of great turmoil in Denmark.

Not too long before, the population had been mainly farm-oriented. Well into the ninth century, Denmark itself was not yet united, but consisted of many regions ruled mostly by "jarls" (what the English would call "earls"). Occasional feuds or wars broke out, but these were relatively minor in the overall scheme of things, and were relatively short-lived. It was late in the eighth century that a new lifestyle started to emerge, to supplement one's basic farming income: at the time, with no big central government or legal system, people took care of their own disputes. If someone from the next farm caused injury or death to someone on your farm, it was perfectly acceptable to return death for death and blow for blow. In doing this, it eventually occurred to them that when exacting revenge on the household down the river, one might as well take some of the household's prized possessions, and just consider that part of the blood debt. The problem with stealing from your neighbors, however, is that they know who you are and where you live: you could pretty much expect that they would return the "favor" at the first opportunity, leaving you with less than you started with. Thus, while such theft might provide temporary satisfaction, it was not really worth the effort in the long run.

"However," they thought, "if we were to make a further trip, to people who didn't know us, then we could take their treasures without fear of retribution!" This was particularly effective when attacking by sea (which was a specialty of these sea-faring people) because they could advance quietly and swiftly, and were hard to pursue when they departed. These early short-range raids eventually reached further and further afield, until the raiders actually started attacking people in other countries. The first recorded international raid was in 793, on the monastery at Lindisfarne in England. Monks were well known for having lots of gold but few weapons, and thus became ideal targets for these raiders. This led to the creation of the most often used Latin prayer of the period, "May God protect us from the fury of the Northmen!"

Thus, the ninth century dawned on a people becoming more and more warlike. The Danes, and indeed the populations from all of Scandinavia, were becoming harder and harder to control. In the tenth century, one leader appeared who was nearly successful in uniting all of Denmark into a single entity: Gorm the Old. He united much of the land, but not all of it. Harald Bluetooth, son of Gorm the Old, completed the work of his father, and became the first king of the united country. It was under Harald's reign that the people were first called "Danes," and it was probably shortly thereafter that the land was first called "Danmark" ("Country of the Danes") in Old Norse, or "Denmark" in English.

United under a powerful king, the nation as a whole began to develop a single army, both for internal affairs and for international wars. One of the most unique architectural structures to come out of this era was the circular "viking fort." Four such forts are known to have existed, though it is possible there were more at the time.

These forts, planted at different strategic locations around Denmark, were perfectly circular to the fraction of an inch. Three were exactly the same size, with a radius of exactly 100 Roman stadia, while the fourth had a radius of 200 stadia. The buildings within each were identical in size and shape, and clustered in perfectly-oriented and spaced quadrangles. These buildings served as barracks, work areas, and storage sheds. The smaller forts contained 16 such buildings; the larger one 48. A wooden plank walkway ran from each of the four entrances to the center of the fort. Surrounding each fortress was a high embankment of wood-reinforced earth, with a wooden walkway around the inside top edge to provide for the greatest defense, and usually with a moat around the outside. When possible, they were built next to a marsh or gully which limited the number of directions from which attackers could appear. Burial of dead soldiers took place outside the walls, in ordered rows.

The structures within the forts were made of wooden poles and planks, with foundation posts sunk into the earth, and even many of the wall planks embedded a bit into the soil. By noting discolorations in the clay-rich soil at these sites, modern archaeologists have been able to determine exactly where and how big these wooden supports were, and thus can determine the shape and location of the buildings within these fortresses. An early reconstruction of one of these buildings stands at one of these sites, but is now known to be inaccurate: the outside row of posts was originally thought to stand straight up, thus serving to hold up eaves around the outside of the building (see picture 4). Yet further study of the soil (after the model building was constructed) showed that the supports were imbedded at an angle, indicating that the posts leaned toward the building (see picture 7). Thus, they either served as triangular braces to the walls, or possibly as the roof beams themselves.

The four known forts were Trelleborg (in eastern Denmark), Fyrkat (in the northeast), Nonnebakken (in central Denmark), and the big one, Aggersborg (in the northwest). Of these, the earthen embankments at the first two have been restored to their original size (see pictures 1, 2, 3, 5, and 6), some of the postholes have been marked to give a sense of the building pattern (see pictures 3, 5, and 6), and the sites have been converted to rather nice outdoor museums. Unfortunately, the latter two have not suffered the same fate: Aggersborg is now a grain field, though from a distance one can yet see a slight circular rise marking the ring of the original wall (see picture 8). Despite centuries of plowing, that much remains. Nonnebakken is now underneath the north side of the city of Odense (the city grew right over the top of it), and we are left with two reminders of its former glory: hand-drawn pictures from the ninteenth century which show the circular embankment still standing; and a sign which stands at its former site, labelling that road as "Nonnebakken Street" (see picture 9).

Modern speculations as to the purpose of these forts mostly follow the "common sense" approach that these must have been training grounds for Danish armies about to embark on acts of conquest in other countries. Yet, if that were the case, why the high walls? Why worry so much about being able to defend themselves, if these points were only meant as the launching point for invasion fleets? And why, if they were navy bases, were some of them so far from water?

In recent years, the Danish population has had to consider a less flattering possibility, hearkening back to the era in which these things were built: this was a time when isolated jarldoms were still being joined together, and not always without a fight. Many jarls or other chieftains, formerly rulers of all they surveyed, did not like the idea of surrendering their power to a distant monarch. They put up a struggle, and had to be violently squelched. This required a nearby, highly-organized army in a secure setting which could guarantee the cooperation of those within their region. This army would be capable of venturing out to quell rebellion, but also had to be able to defend itself from attacks. They were not there to conquer the seaways, but rather the land around them.

The tenth century was a time of great turmoil in Denmark. So turbulent, in fact, that these forts had to be built in order to protect Denmark -- not from outsiders, but from the Danes themselves.

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