Jomsborg

• 1. Introduction

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  Jomsborg was a Viking stronghold on the southern shore of the Baltic Sea, and it may never have existed at all. Somewhere between the 960s and 1043, a fortress rose among the marshes and inlets of what is now northwestern Poland, home to an elite brotherhood of warriors who answered to no king and lived by their own strict code. Or so the sagas say. Historians have been arguing about it ever since. The man who first built it, the warriors who lived there, the battles they fought, the golden disc that surfaced in Sweden in 2014 bearing its name in Latin letters, and the ruins uncovered as recently as 2023 that could finally settle the question, all point toward a place that stubbornly refuses to stay either legend or fact. What exactly was Jomsborg? Where did it stand? And why does its ghost keep turning up in the ground?

• 2. A Fortress in the Marshes

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  The Knytlingasaga and the Fagrskinna both credit the Danish king Harald Bluetooth, who lived from around 910 to 985 or 986, with founding Jomsborg in the 960s. The Jomsvikinga Saga, however, names a different founder entirely: the Danish Viking Palnatoki. Even the basic facts of origin were contested before the debates about location ever began.

  Medieval records describe the fortress itself in detail that grows more impressive with each retelling. The oldest accounts say the harbour held three ships. Later records expanded that figure all the way to 360. Whatever its true capacity, medieval writers agreed that the entrance to the harbour was dominated by a stone tower mounted with catapults, and that an arch spanning the harbour mouth could be sealed shut with an iron gate. The image is of a fortified naval base designed to launch and receive fleets, not merely a village with a waterfront.

  The fortress met its end in 1043, according to the Heimskringla. Dano-Norwegian king Magnus the Good destroyed it that year, burning it to the ground and killing many of its inhabitants.

• 3. The Question of Location

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  The town of Wolin, sitting on the southeastern tip of Wolin island in northwestern Poland, has long been the leading candidate for the site of Jomsborg. In the Early Middle Ages, that same ground hosted a multi-ethnic trading settlement known by names including Jumne and Julin. Nordic sagas used the name Jómsborg exclusively, while medieval German chronicles cycled through a bewildering variety of alternatives: Jumne, Julin, Vimne, Uimne, Jumneta, Juminem, Julinum, Uineta, Vineta, and Vinneta. In 1931-32, Pomeranian historian Adolf Hofmeister, who lived from 1883 to 1956, compared accounts across multiple chronicles and concluded that all these names pointed to the same place, at or near the modern town of Wolin.

  That conclusion has never become settled fact. Professor and historian Steven Fanning has written plainly that all attempts to locate Jomsborg, including efforts to match it with the Trelleborg-type fortresses of Denmark, have failed, and that this failure has led many scholars to doubt the Jomsvikings ever existed outside of literature. Historian Lauritz Weibull went further, dismissing Jomsborg outright as a legend.

  Historian Wladyslaw Filipowiak approached the question differently, pointing to several dated sources that attest to the presence of armed Vikings in Wolin at the close of the 10th century. His reading suggests they may have been installed there as mercenaries by the Polish king Boleslaw the Brave. Ruins uncovered at Wolin in 2023 are now under archaeological investigation as a possible site of the fortress.

  A separate cluster of theories places Jomsborg to the northwest, on lands that now lie underwater off Usedom island. A long stretch of territory between Usedom and Rugen was swallowed by storm floods in the early 14th century. The Veritas grounds, lying between the small islands of Ruden and Greifswalder Oie, and the shoals near Peenemunde have both been proposed as candidates. Viking Age jewelry has been found in the area, but the submerged terrain has so far prevented a proper archaeological evaluation.

• 4. The Brotherhood Within

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  Jomsborg drew its reputation not just from the stone and iron of its harbour but from the men who lived there. The Jomsvikings, as they were known, were a selected group bound by a strict codex and loyal only to their own leader. They were not a royal army or a tribal levy. They were something closer to a professional military order.

  Most records name Sigvaldi, son of the petty king Strut-Harald of what was then Danish Scania, as jarl of Jomsborg. Sigvaldi died sometime before 1010. The Jomsvikings' reputation was built on a series of bold, if not always successful, military expeditions that stretched across the late 10th century.

  Styrbjorn the Strong of Sweden led a force of Jomsvikings from Jomsborg to reclaim the Swedish throne from Eric the Victorious. They met defeat in the Battle of Fyrisvellir, fought near Gamla Uppsala in the mid 980s, probably in 986. A few years later, Sweyn Forkbeard departed from Jomsborg with another Jomsviking contingent to confront jarl Haakon Sigurdsson of Norway, only to lose the Battle of Hjorungavagr, around 990. Olaf I of Norway then joined a Jomsviking force for the Battle of Svolder in 999 or 1000. The pattern is consistent: Jomsborg supplied warriors for the highest-stakes contests of the Viking world, and those warriors often lost.

• 5. The Curmsun Disc

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  In the autumn of 2014, a golden disc appeared in Sweden, brought forward by Swedish archaeologist Sven Rosborn. The object, known as the Curmsun Disc, is made of high-gold-content metal and weighs 25.23 grams. One face carries a Latin inscription; the other shows a Latin cross with four dots set inside an octagonal ridge.

  The inscription on the disc reads: +ARALD CVRMSVN+REX AD TANER+SCON+JVMN+CIV ALDIN+. Translated, that means: Harald Gormsson king of Danes, Scania, Jomsborg, diocese of Aldinburg. The disc names Jomsborg directly, the only physical object known to do so, and it connects the site explicitly to Harald Bluetooth.

  The claimed history of the disc is that it was part of a Viking hoard found in 1841 in the Polish village of Wiejkowo, near the town of Wolin, by a man named Heinrich Boldt. Following his find, Rosborn also located a text purporting to be a modern Polish translation of an otherwise unknown Latin chronicle, the Gesta Wulinensis ecclesiae pontificum. That chronicle is the only source to give a precise geographic location for Jomsborg, situating it near Paprotno, Poland. Rosborn visited the site and reported that it matches the descriptions found in the sagas and chronicles, and that artifacts found on the surface correspond to the period in which Jomsborg existed.

  The Gesta was discovered in the autumn of 2019. But archaeologist Jes Wienberg has criticized Rosborn for not giving other scholars direct access to the finds, making independent evaluation impossible. Historians Kurt Villads Jensen and Wojtek Jezierski have gone further, arguing that both the disc and the chronicle are forgeries. Their case rests on two points: the disc has no known analogue among similar objects from the period, and the chronicle contains several anachronisms. The question of whether the Curmsun Disc is a genuine relic or a modern fabrication remains open, carrying with it the question of whether Jomsborg itself was real.