The Kalmar Union joined together the three kingdoms of Denmark, Sweden and Norway under a single monarch from the year 1397 until the year 1523. The union was formed by Queen Margaret I (1353 - 1413) in the Swedish town of Kalmar after Danish and Swedish troops defeated the Swedish king, Albert of Mecklenburg, in 1389 and he subsequently failed to pay the tribute of 60 000 silver marks within three years after his release. Queen Margaret was the daughter of the Danish king and the wife of Haakon VI of Norway who died in 1387.
Erik of Pomerania, Queen Margaret's grandnephew, was elected as king over the three countries. Queen Margaret promised to protect the political influence and privileges of the aristocrats under the union. King Erik however, wanted to strengthen the monarchy. The Swedes where not happy with this centralizing of government and tried to retain a degree of self government, even to the point of armed rebellion, leading to the expulsion of Danish forces from Sweden. After the successful retaking of Sweden and the subsequent Stockholm bloodbath in 1520 by Kristian II, the Swedes started yet another rebellion that eventually led to the dissolution of the union in 1523 by Gustav Eriksson (Gustav I) of Sweden. The union of Denmark and Norway lasted until 1814.