In 1397, the Kalmar Union was formed uniting Sweden, Denmark and Norway under a single leader. This union was dissolved in 1523 when nobleman Gustav Vasa deposed the Danish king of the Union and became the elected king of Sweden. The Swedes held sway in the Baltic for many years, and from the 1560s repeatedly clashed with Denmark in the Northern Seven Years’ War. In the early 1600s some territories were gained south of the Gulf of Finland; Sweden also possessed Finland and scattered provinces in northern Germany. In 1630, Gustav II Adolphus successfully intervened in Germany in the Thirty Years’ War on the anti-imperialist Protestant side, helping to overcome the Holy Roman Empire and its Catholic allies. He was victorious in war against Denmark 1643–45 elevating Sweden to the status of a great northern European power.
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