Margraviate of Brandenburg fief of the Polish–Lithuanian Commonwealth, to which the electors paid homage. The electors of Brandenburg spent the next two centuries attempting to gain lands to unite their separate territories (the Mark Brandenburg, the territories in the Rhineland and Westphalia, and Ducal Prussia) to form one geographically contiguous domain. In the Peace of Westphalia ending the Thirty Years' War in 1648, Brandenburg-Prussia acquired Farther Pomerania and made it the Province of Pomerania by the Treaty of Stettin (1653). In the second half of the 17th century, Frederick William, the "Great Elector", developed Brandenburg-Prussia into a major power. The state constructed Brandenburg's
Eighty Years' War Roman Empire of 14 and 24 October 1648, which comprise the Peace of Westphalia, but which were not signed by the Republic, the Republic now also gained formal "independence" from the Holy Roman Empire, just like the Swiss Cantons. In both cases this was just a formalisation of a situation that had already existed for a long time. France and Spain did not conclude a treaty and so remained at war until the peace of the Pyrenees of 1659. The peace was celebrated in the Republic with sumptuous festivities. It was solemnly promulgated on the 80th anniversary of the execution