Medieval Scandinavia: War, Plague, and the Beginning of the Kalmar Union

By Beñat Elortza Larrea

For the eighth article in the series, Beñat Elortza Larrea discusses the ravages of famine, warfare and disease in fourteenth-century Scandinavia, culminating with the formation of the Kalmar Union in 1397.

The fourteenth century was a period of crisis and upheaval in Scandinavia and, indeed, the near-entirety of the European continent; a rapid cooling of the climate and the severe effects of the Black Death caused a demographic disaster and a sharp economic downturn, which in turn gave way to societal uproar, revolts and wars. In the Nordic arena, the backdrop created by these structural crises contributed to diplomatic, martial and dynastic issues, as large-scale warfare and conquest among the Scandinavian realms became commonplace.


The societal and political developments of the late thirteenth and early fourteenth centuries had been characterised by increasing inter-Scandinavian entanglement, from both a geopolitical and a dynastic perspective. From the 1280s onwards, large-scale wars had broken out; the murder of Erik V of Denmark, for instance, caused a protracted conflict between the Danes and the Norwegians, who had given refuge to the alleged murderers. The fraternal wars in Sweden in the early fourteenth century, which pitched Birger Magnusson against his younger brothers Erik and Valdemar, were marked by considerable Danish and Norwegian intervention. Birger sought the support of Erik VI of Denmark, his brother in law, while Duke Erik Magnusson’s marriage with the daughter of Håkon Magnusson secured Norwegian support for the rebels.

Duke Erik, indeed, attempted to form his own central Scandinavian kingdom, which straddled Norwegian lands, western Sweden, and recent Norwegian conquests in Denmark; the murder of the dukes at the hands of their brother Birger in 1318, however, rapidly dispelled such an eventuality. While briefly victorious, Birger’s act of fratricide was met by fierce opposition from the Swedish nobility, who deposed the king and placed Duke Erik’s infant son, Magnus Eriksson, on the throne; since Håkon V Magnusson died without male heirs in Norway, both kingdoms entered into a personal union under young Magnus.


The results of these lengthy wars were even more dramatic in Denmark. Erik VI engaged in long wars against Norway, his rivals in the German principalities and in Sweden. Unable to pay the extensive bodies of mercenaries he employed, Erik mortgaged parts of Denmark as security, but since these campaigns were largely unfruitful, the Danish rulers were unable to pay their debts. Following the death of Erik’s brother and successor, Christoffer II, in 1332, the Danish realm ceased to exist, as different German debtors took over the territories they had been promised.

The German princes were initially well-received, as they promised not to implement unfair taxes, but this situation would not last long. Peasant revolts became increasingly common, and in 1340, a Danish force, led by the squire Niels Ebbesen, murdered one of the major German lords, Gerhard III of Holstein-Rendsburg. Although Niels and his supporters were soon defeated and killed, Christoffer’s son Valdemar saw his chance, and secured his election as Danish king the same year.

Map detailing the division of Denmark 1332-1340 – by Vesconte2 / Wikimedia Commons

In addition to increasing conflicts and instability, several centuries of population growth and a sharp climatological turn further exacerbated tensions. By the early 1300s, the population of Europe had been steadily rising for around three centuries, aided by warm winters, mild summers and plentiful harvests. Population growth, however, was largely reliant on extensive farming; to this end, forests had been cleared to make way for settlements and more arable land. By the turn of the fourteenth century, however, this expansive agricultural system was in crisis, since in many areas farming communities had simply run out of land. Localised shortages became common, winter stores were depleted to avoid famine, and lower caloric intake made the general population more vulnerable to disease.

To make matters worse, this population crisis coincided with the opening stages of the Little Ice Age that affected Europe around between the early fourteenth and mid-nineteenth centuries; the chief effect of the rapid cooling was the Great Famine, which affected northern Europe between 1315 and 1322. The Danish Annals of Essenbæk aptly highlight the hardships that the famine brought with it: in addition to starvation, disease outbreaks and revolts became commonplace, as farming communities struggled to navigate the ravages of warfare, famine and unforgiving taxation.


Magnus Eriksson’s minority was relatively uneventful, as aristocratic councils ruled in his stead; following his coming of age in 1331, however, tensions between the young king and the aristocracy became commonplace. Magnus resided in Sweden and ruled from his residences there, which alienated his Norwegian subjects, especially after the king refused to nominate a chancellor for Norway; angered, the Norwegian aristocracy forced Magnus to appoint his son Håkon VI as Norwegian king in 1343, which would take place after Håkon’s coming of age in 1355.

Magnus Eriksson on the title page of his Swedish national lawcode, issue 1430.

Before the personal union could be severed, however, the Black Death arrived in Scandinavia, possibly when a plague-stricken ship moored in Bergen in 1349. The consequences in Sweden were dire, with about a third of the populace dying, but Norway was hit particularly hard, with at least half the population dying; plague victims, of course, included aristocrats and ecclesiastical figures as well as ordinary peasants, which significantly reduced the cohesiveness and collective power of the Norwegian aristocracy. Following the Black Death, Magnus continued to favour large-scale expansionist campaigns and ruled through his favourites; the growing fiscal pressure and unfair favouritism alienated the Swedish aristocracy, who deposed Magnus and elected a German prince, Albrecht of Mecklenburg, as king in 1364. Isolated and crownless, Magnus would take refuge at his son’s court in Norway and died in 1374.

The challenges faced by Magnus Eriksson were beneficial to Valdemar IV of Denmark, who managed to recover most of his Danish possessions by the end of the 1340s; Scania, however, remained in Swedish hands, as it had been swiftly occupied by Magnus soon after Christoffer II’s death in 1332. Valdemar’s immediate plans to recover Scania in the late 1340s had to be abandoned due to the arrival of the Black Death. Although the effects on the Danish population were not as dramatic as in Norway – around a third of the population succumbed to the plague in Denmark –, agricultural production suffered in the aftermath of the plague, and landowning nobles and peasants, encumbered by taxation, rebelled often. After offering settlements to some of his aristocrats and crushing pockets of resistance, Valdemar supported a rebellion against Magnus Eriksson in Scania; when the revolts’ instigator, Magnus’s son Erik, died, Valdemar demanded Scania in exchange for his retreat, and the region was returned to Denmark in 1360. During the latter part of his reign, Valdemar invaded and conquered the island of Gotland as part of his policy to restrain the influence of the Hanseatic League in the Baltic; accosted by the merchant cities, Swedes and Norwegians, however, the Danish king was eventually forced to concede, and died in 1375.


Valdemar’s successes, however, were not simply reliant on his martial ability and ruthless behaviour; in order to cement his dominant position in Scandinavia, the Danish king also conducted crafty marriage negotiations. Valdemar married his daughter Margrete to Håkon VI Magnusson, who had acceded the Norwegian throne in 1343. The main goal of this match must have been to bring the three Scandinavian realms closer together, as Håkon was poised to inherit Sweden from his father; the election of Albrecht as Swedish king in 1364, however, dashed these hopes. Since Valdemar survived his sons, it would be his grandson – Margrete’s son Olav – who inherited the Danish kingdom in 1376; Olav’s father Håkon VI, moreover, died in 1380, thus making the ten-year-old aristocrat ruler of both countries. When Olav died in 1387, aged sixteen, the only individual with the dynastic status to accede the throne was his mother, Margrete.

Queen Margaret I of Denmark, effigy from 1423 on her tomb in Roskilde Cathedral. Photo by Jacob Truedson Demitz / Wikimedia Commons

Margrete proved herself as a shrewd and resourceful ruler; during her son’s minority, she had already managed to re-establish Danish control over Schleswig, and she was widely supported by Danish and Norwegian aristocrats alike. Since Albrecht was widely opposed in Sweden, Margrete saw the opportunity to fulfil her father’s wildest expansionist dreams, and agreed to assist the Swedish aristocracy against their king in exchange for her election as ruler. In 1389, Albrecht’s forces were soundly defeated in Åsle, and Margrete became the effective ruler of Denmark, Norway and Sweden. Her womanhood, however, proved a hurdle; she was never recognised as reigning queen, and her rule hinged upon her finding a suitable male heir who could be crowned as triple king. As part of this agreement, she chose her great-nephew, Erik of Pomerania (born Boguslaw), who was brought up in Denmark from 1389 onwards. Margrete was supposed to act as regent until young Erik came of age, but in practice, Margrete remained in charge until her death in 1412.

The formal establishment of a personal union among the Scandinavian kingdoms took place in 1397, during Erik’s coronation festivities at Kalmar in June of 1397. Two foundational documents were signed during these meetings: the Coronation Charter and the Union Charter, which were sponsored by the Crown and the aristocracy, respectively. These two charters highlighted the goals and aspirations that each faction had, and indeed foreshadowed the internal conflicts that would happen in the near future. Margrete and Erik sought the establishment of a strong monarchy with sweeping powers across the Union, which could make use of the large resources and manpower available to establish itself as a regional power. The aristocracy, on the other hand, expected a royal power limited by the existing laws and customs of each kingdom, which would rule the diverse and expansive union through aristocratic cooperation and participation; most notably, the Union Charter spoke against appointing foreign castellans in each kingdom and favoured elective kingship.

Margrete and Erik ruled following the conventions of the Coronation Charter, understanding that the ruler was the law, rather than limited by the law. Denmark became the uncontested centre of power, neither Margrete nor Erik visited the other two kingdoms often, and Danish or German castellans were appointed as administrators throughout the Kalmar Union. While discontent grew, there was no open reaction to royal rule while Margrete was alive, but aristocrats and peasants alike began to voice their dissent after her passing in 1412. Throughout the fifteenth century, tensions between proponents of unfettered royal rule – regimen regale – and more participatory aristocratic governance – regimen politicum – would lead to bloody conflict in the Kalmar Union, causing it to tear asunder on the eve of the Early Modern Period.


Beñat Elortza Larrea is an Associate Professor at Nord University. His research interests include state formation in medieval Scandinavia, military history from a social perspective, and maritime societies in the Middle Ages. Click here to visit his page on

Click here to read more from Beñat’s series on Medieval Scandinavia

Top Image: Map of the Kalmar Union in 1397 – Wikimedia Commons