Sigismund	Charles IX	Gustavus Adolphus	Christina
Charles X	Charles XI	Charles XII

Sweden (which included Finland) was virtually 100% Lutheran in the 17th Century. Sigismund, who acceded to the throne in 1594 had been elected King of Poland in 1587. He attempted to introduce Roman Catholicism in Sweden and was promptly deposed (1599). (He remained King of Poland - Sweden's major economic rival  -  until his death in 1632). Sigismund was related to the Catholic Habsburgs who were attempting to control the Protestant princes of Germany. Religious fervor, economic self-interest, and political and dynastic self-preservation all motivated the Swedes to help the Protestants in the Thirty Years War.

Under Gustavus Adolphus and Christina, Swedish power grew. Its efficient armies, supplied by arms domestically manufactured from Sweden's major copper and iron mines, fought throughout Germany and Central Europe, while its navy dominated the Baltic. Sweden conquered areas of Norway and territory on the Baltic's southern shores. Charles XII tried to extend Swedish power still further, fighting Denmark, Prussia, Poland and Russia, but was finally defeated.