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 the intermarriage was the incorporation of the lower
Rhenish principalities of
Cleves,
Mark and
Ravensberg after the
Treaty of Xanten in 1614. The
Thirty Years' War (1618–48) was especially devastating. The Elector changed sides three times, and as a result Protestant and Catholic armies swept the land back and forth, killing, burning, seizing men and taking the food supplies. Upwards of half the population was killed or dislocated. Berlin and the other major cities were in ruins, and recovery took decades.