Kalmar Union

The Kalmar Union (Danish, Norwegian, and ; ) was a personal union in Scandinavia, agreed at Kalmar in Sweden, that from 1397 to 1523 joined under a single monarch the three kingdoms of Denmark, Sweden (then including most of present-day Finland), and Norway, together with Norway's overseas 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. However, 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 eleven days later, marked Sweden's final secession from the Kalmar Union. Formally, the Danish king acknowledged Sweden's independence in 1524 at the Treaty of Malmö.
Inception.
The union was the work of Scandinavian aristocracy wishing to counter the influence of the Hanseatic League. More personally, it was achieved by Queen Margaret I of Denmark (1353–1412). She was a daughter of King Valdemar IV 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 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. The following year, 1388, Swedish nobles called upon her help against King Albert. After Margaret defeated Albert in 1389, her heir Eric was proclaimed King of Norway. Eric was subsequently elected King of Denmark and Sweden in 1396. His coronation was held in Kalmar on 17 June 1397.
One main impetus for its 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. 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. Charles Bonde, for example, was made king of Sweden three times by nationalists there, in 1440, 1464 and 1467.
End and aftermath.
The Union lost territory when the Northern Isles 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 islands were annexed by the Kingdom of Scotland.
In practice, the Kalmar Union fell apart when Sweden rebelled and became independent on 6 June 1523 and Gustav I of Sweden was elected as king there. After the Northern Seven Years' War, the Treaty of Stettin (1570) saw Frederick II renounce all claims to Sweden, officially dissolving the union.
One of the last structures of the Union remained until 1536/1537 when the Danish Privy Council, in the aftermath of the Count's Feud, unilaterally declared Norway to be a Danish province: this did not happen; instead, Norway became a hereditary kingdom in a real union with Denmark. Norway continued to remain a part of the realm of Denmark–Norway under the Oldenburg dynasty for nearly three centuries, until it was transferred to Sweden in 1814. The ensuing union between Sweden and Norway lasted until 1905, when prince Carl of Denmark, a grandson of both the incumbent king of Denmark and the late king of Sweden, was elected king of Norway.