BRANDENBURG, the name of a margraviate and electorate which played an important part in German history, and afterwards grew into the kingdom of Prussia. During the early years of the Christian era, the district was inhabited by the Semnones, and afterwards by various Slavonic tribes, who were partially subdued by Charlemagne, but soon regained their independence. The history of Brandenburg begins when the German king, Henry the Fowler, defeated the Havelli, or Hevelli, and took their capital, Brennibor, from which the name Brandenburg is derived. It soon came under the rule of Gero, margrave of the Saxon east mark, who pressed the campaign against the Slavs with vigour, while Otto the Great founded bishoprics at Havelberg and Brandenburg. When Gero died in 965, his mark was divided into two parts, the northern portion, lying along both banks of the middle Elbe, being called the north or old mark, and forming the nucleus of the later margraviate of Brandenburg. After Otto the Great died, the Slavs regained much of their territory, Brandenburg fell again into their hands, and a succession of feeble margraves ruled only the district west of the Elbe, together with a small district east of that river.
A new era began in 1106 when Lothair, count of Supplinburg, became duke of Saxony. Aided by Albert the Bear, count of Ballenstädt, he renewed the attack on the Slavs, and in 1134 appointed Albert margrave of the north mark. The new margrave continued the work of Lothair, and about 1140 made a treaty with Pribislaus, the childless duke of Brandenburg, by which he was recognized as the duke's heir. He took at once the title margrave of Brandenburg, but when Pribislaus died in 1150, a stubborn contest followed with Jazko, a relation of the late duke, which was terminated in 1157 in Albert's favour. Albert was the real founder of Brandenburg. Under his rule Christianity and civilization were extended, bishoprics were restored and monasteries founded. The country was colonized with settlers from the lower Rhineland, land was brought under cultivation, forts were built, German laws and customs introduced, and gradually the woods and marshes were converted into lands of comparative fertility.