In 1397, the three kingdoms of Denmark, Norway and Sweden (including most of Finland) became allied under a single monarch by the Kalmar Union (so called after the town in southeast Sweden), and in 1460 the Germanic province of Holstein was also incorporated. The Union was formed to counter the growing trading power of the German-dominated Hanseatic League, and ended in 1523 when Sweden seceded. In the east, the power of the German-speaking Teutonic Order of Knights began a steady decline after their heavy defeat by a Polish-Lithuanian alliance at the Battle of Tannenberg in 1410. In the aftermath, the branch Livonian Order, which had not participated in the battle, began to separate from the Teutons. In the Gollub War of 1422, the Orders jointly lost Samogitia to the Duchy of Lithuania, and in 1435 the Livonian Order was heavily defeated by Polish and Lithuanian forces at the battle of Wilkomierz. By 1521, after three wars against the Poles, the Orders had become fully separated and were ousted from Prussia altogether. In 1560 the Russian victory at Ērģeme was the last battle fought by the Livonian Knights, after which the Order disbanded. This dwindling of German authority heralded an era during which power in the region would become contested between the Kalmar nations, Sweden, Poland, Lithuania and Russia.
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