The Kalmar Union was a personal union<!-- Election of Christian II as king was 1513 in Denmark and Norway, 1520 in Sweden --> in Scandinavia, agreed at Kalmar in Sweden as designed by Queen Margaret of Denmark. From 1397 to 1523, it joined under a single monarch the three kingdoms of Denmark, Sweden (then including much of present-day Finland), and Norway, together with Norway's maritime colonies (then including Iceland, Greenland, the Faroe Islands, and the Northern Isles of Orkney and Shetland).
The union was not quite continuous; there were several short interruptions. Legally, the countries remained separate sovereign states, but their domestic and foreign policies were directed by a common monarch. Gustav Vasa's election as King of Sweden on 6 June 1523, and his triumphant entry into Stockholm 11 days later, marked Sweden's final secession from the Kalmar Union. Frederick I formally renounced his claim to Sweden in 1524 at the Treaty of Malmö.
thumb|The Kalmar Union. Denmark, Sweden, Norway. But also Finland, Iceland, the Åland Islands, the Faroe Islands, Greenland, Svalbard, Jan Mayen, Orkney and Shetland. Along with Schleswig, Holstein, Lauenburg, Oldenburg, Pomerania, Estonia, Latvia, Lithuania and Konigsberg
History
Inception
The union was the work of Scandinavian aristocracy who sought to counter the influence of the Hanseatic League, a northern German trade league centered around the Baltic and North Seas. Denmark in particular was in a power struggle with the League and had recently suffered a humiliating defeat in the Danish-Hanseatic War (1361-1370) that allowed the League to become even more powerful. On the personal level, the union was achieved by Queen Margaret I of Denmark (1353–1412). She was a daughter of King Valdemar IV of Denmark and had married King Haakon VI of Norway and Sweden, who was the son of King Magnus IV of Sweden, Norway and Scania. Margaret succeeded in having her and Haakon's son Olaf recognized as heir to the throne of Denmark. In 1376, Olaf inherited the crown of Denmark from his maternal grandfather as King Olaf II, with his mother as guardian; when Haakon VI died in 1380, Olaf also inherited the crown of Norway.
Margaret became regent of Denmark and Norway when Olaf died in 1387, leaving her without an heir. She adopted her great-nephew Eric of Pomerania the same year. In 1388, Swedish nobles called upon her help against King Albert. After Margaret defeated Albert in 1389, her heir Eric was proclaimed King of Norway.
One main impetus for the union's formation was to block German expansion northward into the Baltic region. The main reason for its failure to survive was the perpetual struggle between the monarch, who wanted a strong unified state, and the Swedish and Danish nobility, which did not.
The Union lost territory when Orkney and Shetland were pledged by Christian I, in his capacity as King of Norway, as security against the payment of the dowry of his daughter Margaret, betrothed to James III of Scotland in 1468. The money was never paid, so in 1472 the Kingdom of Scotland annexed the islands.
Internal conflict
Diverging interests (especially the Swedish nobility's dissatisfaction with the dominant role played by Denmark and Holstein) gave rise to a conflict that hampered the union in several intervals starting in the 1430s. The Engelbrekt rebellion, which started in 1434, led to the overthrow of King Erik (in Denmark and Sweden in 1439, as well as Norway in 1442). The aristocracy sided with the rebels.
End and aftermath
One of the union's last structures remained until 1536/1537, when the Danish Privy Council, in the aftermath of the Count's Feud, declared Norway a Danish province. In practice, Norway kept its status as a separate kingdom and its own laws, but its council and other central institutions were dissolved, and it became politically subordinate to Denmark. This Denmark–Norway union lasted nearly three centuries, until Norway was ceded to Sweden in 1814. The later Swedish–Norwegian union lasted until 1905, when Prince Carl of Denmark was elected king of independent Norway.
According to historian Sverre Bagge, the Kalmar Union was unstable for several reasons: