Trelleborg eller ej? om den skånske trelleborgs tilknytning til de danske ringborge

                                A Viking fortress? On the possible connection between the Trelleborg fortress in Scania and the Danish Viking fortresses In 1988-1991, Swedish archaeologists excavated a circular fortress from the Viking Age in Trelleborg, the southernmost town of Scania (fig. 1). The structure consisted of two rampart phases (fig. 6A), which were both dated using a series of Carbon-14 analyses (primarily of charcoal from fireplaces underneath -and thus older than- the rampart phases, and of a few pieces of charcoal found in the moat. All the Carbon-14 results are listed in figs. 3 and 4) -as the conditions prohibited the using of dendrochronological analyses, and it was impossible to separate those finds that belonged to the function period of the fortress. The Carbon-14 results made the excavator conclude that the older phase, phase 1, was probably built during the first half of the 10th century, and that the extension and reinforcement belonging to phase 2 were made sometime during the second half of the 10th century. (7) The second phase of the fortress was very quickly interpreted as a new example of the Viking fortress from the late Viking Age, which was previously only known from four localities within the present boundaries of Denmark. The four Danish circular fortresses are Trelleborg near Slagelse on Sjælland, Nonnebakken in Odense on the island of Fyn, Fyrkat near Hobro in Northern Jutland, and Aggersborg by the Limfjord, also in Northern Jutland. These four fortresses, which all follow a strict circular and geometrical layout, all date from c 980 (16) and are thought to have been built by King Harold Bluetooth. Although the fortress in Scania differs from the Danish fortresses in several ways, (8) the Swedish excavator has maintained that it was a local variation of the Danish circular fortresses built by King Harold Bluetooth, and that it differed from the rest only in detail. However, a closer study of the Swedish material causes immediate doubts as to the claimed resemblance. There are some similarities -such as a circular rampart built of earth and peat with four possible gates (9) placed roughly at the four points of the compass; an outer rampart covering made up by a vertical palisade, against which was built a slanting escarpment behind a berm and moat -but the differences when compared with the Danish fortresses are striking (figs. 5 and 6). First, the fortress in Scania does not follow the very strict geometrical system, which is such a striking feature of the Danish fortresses. The rampart does not describe an exact circle; the gates deviate from the points of the compass, and nothing suggests that the Scanian fortress had any regular block settlement or the special road system known from Denmark. In fact, no traces of a permanent settlement contemporary to the fortress were found within the fortress area. (13) Other essential differences are the lack of an inner timber structure in the rampart, a trough-shaped moat as opposed to the V-shaped moats in the Danish fortresses, gates of different dimensions, and an inner side of the ram part that did not have a vertical plank covering, but was gently sloping towards the courtyard. These differences cannot be explained as a local Scanian variety of the Danish Viking fortress. The Danish fortresses obviously were the product of a strong and controlling idea, which was more important for their construction than the local conditions in the chosen locations. The violent destruction of existing settlements at the Trelleborg and the Aggersborg sites testify to this, as do the extensive landscape changes that were necessary before Trelleborg and Fyrkat could be built. The strictly geometrical structure and the stringent observance of it seem to be one purpose of the Danish fortresses -a demonstration of the power of their founder. This circumstance conforms to the fortresses being attributed to Harold Bluetooth, as this king also displayed his considerations as to prestige when he initiated the Jelling monuments. King Harold is not likely to have allowed the construction of a fortress with a less strict design in Scania. The founder of the Danish fortresses did not compromise with the observance of the overall plan. The dating of the fortress in Scania is also questionable. To begin with, it does not seem convincing when several very wide Carbon-14 dates of stratigraphically older layers (figs. 3 and 4) are being fitted into the later fortress, which in turn is given a very narrow historical context. Also, the excavator's interpretation of the Carbon-14 dates is debatable. Most of the samples from structures in phase 1 are Carbon-14-dated to the time between the late 7th century and the late 9th century (calibrated with one standard deviation). However, the excavator attaches great importance to one sample (from structure no. 1144), the middle value of which is the year 891. It therefore spans a somewhat later time interval than the rest of the analyses: 827-986. This result is an important factor for the dating of phase 1 to the first half of the 10th century, as it makes it possible that the settlement activity, which preceded the fortress, lasted well into the 10th century. However, the result of the analysis does not support such an interpretation, especially as we are dealing with just one Carbon-14 result with one standard deviation. Whereas Carbon-14 dating with two standard deviations gives wide but very certain time frames, the uncertainty attached to dating frames with just one standard deviation corresponds to a dating, which in one third of the cases differs from the achieved time frame. With an uncertainty like this, it is too risky to attach too much importance to just one result, a dating frame with only half of its values reaching into the 10th century. The excavator is right in establishing that phase 2 cannot be many decades younger than phase 1, as the dug-in timber from the gates, which functioned both during phase 1 and phase 2, have no traces of the repair that the damp climate of southern Scandinavia would have required after relatively few years. However, he dates phase 2 using just three, very wide, Carbon-14 dating frames. These stem from stray pieces of charcoal found at the bottom of the moat (20) (fig. 4). This is a very frail foundation for a dating, and the attempt to attach phase 2 to the late 10th century on this basis is problematic. The excavator argues that the moat must have been either constructed or dredged in connection with the construction of phase 2 and that the charcoal from the bottom of it must therefore have been deposited then. Yet, it appears from the excavation results that the moat functioned as a drainage canal for the medieval settlement and even had several drainage ditches connected to it. (21) It is difficult to imagine that the moat would have had this function for several centuries after the abolition of the fortress without being dredged. The charcoal may just as well have been deposited during later dredging, and this removes the essential basis for the assertion that phase 2 dates from the late 10th century. Using the available data, the fortress in Scania cannot be given a more precise dating than the Viking Age. Thus, the arguments concerning typology and dating do not support the attempt to place the Trelleborg fortress in Scania in the narrow historical context of the four geometrical Viking fortresses in Denmark. It would be wrong to deny certain similarities between the two fortress types, but the Danish fortresses seem to represent a straightening-up or perfection of the plan used for the fortress in Scania. Thus the two types do not represent one single fortress type, but rather two links in a fortress development. A fortress type represented by five or six sites in the Zeelandic-Flemish region on the south coast of the North Sea (fig. 8) may support the theory of a fortress development. The fortresses here were circular ramparts made from clay and peat surrounded by water-filled moats of a considerable size. Each fortress had four gates placed at a c 20-degree deviation from the four points of the compass. Diagonal streets connected the gates, which divided the courtyard into four quarters. These fortresses are dated to the last quarter of the 9th century (24) -a time when the region was exposed to massive Viking attacks, and the fortresses are therefore regarded as a defence against the Vikings. (25) As early as this the Scandinavians must have known this fortress type. It is worth considering whether the Trelleborg fortress in Scania -which could easily be from the same time as the Zeelandic-Frisian fortresses- may represent a first attempt to transfer a well-known European fortification type to Scandinavia, perhaps because the people living on the southern coast of Scania had a similar defence problem. The fortress in Scania could then be fitted into the role as a stronghold, which may explain the absence of traces of a permanent settlement within the fortress area. Who the enemy was is unknown, but the Viking Age was a turbulent period, and both written and archaeological sources testify to this also having been the case in the Baltic. (26-31) Martin Borring Olese