Part of the Brandenburg history is that the state was amongst the seven key states of the Holy Roman Empire. It was recognized as the unique core of the German Empire along with Prussia, which was the first united German state.
The Margraviate and the Duchy of Prussia joined hands in the year 1618 to form Brandenburg-Prussia. In 1701, the state was prominent as the Kingdom of Prussia. In the early 900s, Henry the Fowler and his successors occupied territory up to the Oder River. Slavic settlements such as Brenna, Budusin, and Chosebuz came under grand control through the installation of Margraves. In 948, Emperor Otto I established Margraves to exert grand control over the pagan Slavs west of the Oder River.
The turning point was the 12th century when the Ottonian German kings re-established control over the mixed Slav-inhabited lands of Brandenburg.
The German magnate Albert the Bear formally inherited the town of Brandenburg and the lands of the Hevelli from their last Wendish ruler, Pribislav, in 1150 and was granted the Northern March by the Emperor Lothar II in 1134, when the German crusade raised against the Wends. Albert’s descendant Ascanians began acquiring country east of the Oder, later recognized as the Neumark in the 13th century.
The Brandenburg history was afterward transformed to Protestantism in 1539 in the wake of the Protestant Reformation. The Hohenzollerns extended their region by acquiring the Duchy of Prussia in 1618, the Duchy of Cleves (1614) in the Rhineland, and territories in Westphalia.
Result was an extensive, disconnected country known as Brandenburg-Prussia.