Northern March
The tribes west of the Oder were organized in marches of the Ottonian (Liudolfing) realm, which became the Holy Roman Empire with the coronation of Otto I, Holy Roman Emperor in 962. The marches set up in the area of the future Brandenburg and Pomerania were the Billung March in the north, and the Saxon Eastern March in the south; the boundary was the Peene river. The Saxon Eastern March was soon partitioned, with the area of future northern Brandenburg and southwestern Pomerania re-organized in the Northern March. A rebellion of the Liuticians overthrew the margraves' rule in most of the Northern and Billung marches between 983 and 995. In the 11th century, the Liutician confederation collapsed due to internal struggles, leaving its territory vulnerable to its neighbors' campaigns, including expeditions of the margraves of the Northern March.