The Second Northern War (1655–60), was fought between Sweden and its adversaries the Polish–Lithuanian Commonwealth (1655–60), the Tsardom of Russia (1656–58), Brandenburg-Prussia (1657–60), the Habsburg monarchy (1657–60) and Denmark–Norway. The Dutch Republic waged an informal trade war against Sweden and seized the colony of New Sweden in 1655, but was not a recognized part of the Polish–Danish alliance.

Brandenburg-Prussia is the historiographic denomination for the early modern realm of the Brandenburgian Hohenzollerns between 1618 and 1701. Based in the Electorate of Brandenburg, the main branch of the Hohenzollern intermarried with the branch ruling the Duchy of Prussia, and secured succession upon the latter's extinction in the male line in 1618. Another consequence of intermarriage was the incorporation of the lower Rhenish principalities of Cleves, Mark and Ravensberg after the Treaty of Xanten in 1614.