March 8: The Treaty of Roskilde was the result of seven years of devastating European Northern wars and by which the King of Denmark-Norway was forced to give up half of his territory to Sweden in 1658.

The Peace of Westphalia did not solve the problem of the countries in the Baltic Sea. Sweden became the power of the area after invading Poland and Lithuania that had been weakened by religious conflicts.

The peace banquet (Fredstaffelet) at Frederiksborg Castle following the signing of the Treaty of Roskilde in 1658.

Charles X Gustav of Sweden took over Krakow and Warsaw in 1655 which generated an antiswedish reaction that included all northern neighbors.
Sweden defeated Denmark in two wars: between 1643 and 1645, and then in 1657-58 that led to the Peace of Roskilde, signed in 1658, by which Sweden Denmark ceded control of the Sound, Gotland Island, plus Bohuslän, Jämtland and Härrjedland besides Blekinga regions, Skåne and Halland located on the Scandinavian Peninsula.

The Swedish territories on the map are:

1) Kexholm-Karela County
2) Swedish Ingermanland (Ingria)
3) Swedish Estonia 
4) Livonia
5) Swedish Pomerania, Bremen and Verden
6) Scania, Halland, Gotland and Bohuslän
7) Jämtland, Härjedalen, Idre and Särna
8) Trøndelag and Møre og Romsdal

It is noteworthy that the Swedish empire besides Germanic territories, Finland had a colony in North America, where today is the State of Delaware, USA.

With the Peace of Roskilde, Sweden also acquired the provinces of Skåne, Halland, Blekinge, Bohuslän, and established the modern borders of Sweden since 1658.