From 1397 to 1523 Scandinavia had been politically united under the Danish crown. The Kalmar Union had been created, which allowed three Scandinavian states: Denmark, Sweden and Norway to present a united force against foreign and German encroachments. Queen Margaret I of Denmark was the driving force, she who had become Queen of Norway through marriage, and Queen of Sweden by joining of forces against the unpopular German King.
Under the Kalmar Union, European monarchs expanded their royal power, bringing them into conflict with their nobles. The union eventually folded as Danish and Swedish monarchs could no longer work together as both factions clashed, resulting in warfare.
Warfare took place between Denmark and Sweden, which diverted Finland’s eastern defences leaving it open to attack by the Muscovites. In the latter part of the 15thcentury, the Grand Duchy of Muscovy had carried out expansion, which would become part of the Russian Empire. In 1478 Grand Duke Ivan III, brought Muscovite power to Finland’s border. In 1493 Denmark and Muscovy made a treaty of alliance, aimed at creating Sweden in a two-front war, and in 1495 Muscovite forces invaded Finland. The Fortress of Viipuri survived the attack, leaving large areas of Finland’s borders in devastation. In 1497 Swedes made peace with Muscovy. Swedish – Finnish forces defended Finland, with little assistance from Sweden.
Swedish noble; Gustav Vasa led a revolt against the Kalmar Union, which led to the creation of a Swedish state, separate from Denmark in 1523. Vasa became King Gustav I Vasa of Sweden, founding a dynasty, ruling Sweden – Finland for more than a century. He will be remembered for the creation of Sweden’s modern state, and under his rule Finland and Sweden remained an integrated state.