Excerpts from Books and Wikipedia
"The Battle of Brunkeberg was fought on 10 October 1471 between the Swedish regent Sten Sture the Elder and forces led by Danish king Christian I." [Wikipedia] "The Battle of Brunkeberg not only saved the nascent Swedish nation state from being submerged in a Danish-dominated Scandinavian union but saw a modern, professional army defeated and routed by a committed and well-organized peasant militia. . . . A royal army of 6000 Danish regulars and German mercenaries led by King Christian I Oldenburg of Denmark, opposed an army of 10,000 Swedish peasant levies led by Sten Sture. . . . The Danes overconfidently charged the Swedes, who, using superior numbers and knowledge of the local terrain, encircled and defeated their foe. . . . In 1397 the three kingdoms of Denmark, Norway and Sweden--with the Grand Duchy of Finland--created a union, with Queen Margaret of Denmark (1353-1412) as head of state. Due to the mutual suspicion and antagonism of the Danes and Swedes the union functioned poorly and when Margaret died in 1412 the Swedes broke away." They chose Charles VIII as their king, but when he died in 1470, King Christian I saw his chance to regain the throne.