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
Treaty of Altranstädt (1707) Treaty of Altranstädt (1707) The Treaty or Convention of Altranstädt was signed between Charles XII of Sweden and Joseph I, Holy Roman Emperor on 31 August 1707. It settled the rights of Protestants in Silesia. While the Protestant Reformation had strongly affected Silesia, the Habsburg emperors had subjected the province to the counter-reformation in the 18th century. Especially in Upper Silesia, these measures were successful: in the early 18th century, almost half of the Silesian population was Roman Catholic and some 1,000 churches had been rededicated from Protestant to Roman Catholic. The Peace of Westphalia (1648) protected Protestants only in