Northern War of 1655–60

a war between Sweden and its allies and the Polish-Lithuanian Commonwealth (Rzeczpos-polita). Sweden wanted to gain control over the Prussian and Lithuanian coast of the Baltic region, which belonged to the Polish-Lithuanian Commonwealth, and establish its supremacy on the Baltic Sea.

The Northern War of 1655–60 broke out during the Russo-Polish War of 1654–67. Invading the Polish-Lithuanian Commonwealth in July 1655, Swedish forces quickly occupied almost all of the Polish lands, including Warsaw and Kraków, as well as part of Lithuania. The majority of the Polish magnates and some members of the gentry (szlachta) recognized the authority of the Swedish king Charles X Gustavus. A peasant uprising against the occupiers in the Kraków piedmont in December 1655 laid the foundation for the expulsion of the invaders. The liberation of Poland was facilitated by a truce between the Polish-Lithuanian Commonwealth and Russia in the spring of 1656 and by the outbreak of the Russo-Swedish War of 1656–58.

In the summer of 1656, however, the Swedes, allied with Brandenburg, recaptured Warsaw. The Polish-Lithuanian Commonwealth received support from Austria and won Brandenburg’s support by renouncing its sovereign rights in East Prussia in the Wehlau-Bydgoszcz Treaty of 1657. Swedish forces left the territory of the Polish-Lithuanian Commonwealth after Denmark’s entry into the war against Sweden in June 1657. Denmark was defeated and compelled to leave the war in early 1658, losing Skåne and other territories in the Peace of Roskilde (1658). The war resumed in the same year, but Sweden failed in its attempt to subjugate Denmark (the siege of Copenhagen, for example). Denmark was supported not only by the Polish-Lithuanian Commonwealth, Austria, and Brandenburg but also by the Netherlands.

In 1660 the Polish-Lithuanian Commonwealth, intending to take possession of the Ukraine, which had been united with Russia in 1654, and Byelorussia, most of which had been occupied by Russian forces in 1654–55, concluded a treaty with Sweden regarding the maintenance of the status quo (the Peace of Oliva). Denmark’s war against Sweden ended with the Treaty of Copenhagen (1660), under which Denmark regained part of the territories it had lost. The Polish-Lithuanian Commonwealth resumed the war against Russia in 1659, forcing Russia to conclude an unfavorable treaty with Sweden—the Treaty of Kardis(1661).