The County developed out of the possessions of the Brunonen dynasty centered on the town of Brunswick and was enlarged by the inheritances of Henry the Fat of Northeim around Northeim and Göttingen and a part of the Billung inheritance around Lüneburg, which fell to the House of Welf in 1106.
The village of Wittenburg is the site of a former Augustininan canons regular monastery, established in the 14th century in the place of a former castle, maybe erected by members of the Billung dynasty as early as 805.
On the Saxon side, in addition to Count Otto of Northeim and Bishop Burchard II von Halberstadt, were Magnus Billung, meanwhile Duke of Saxony, Margrave Lothair Udo II of the Nordmark and Count Gebhard of Supplinburg, who was killed in battle, as well as the Saxon count palatine Frederick II of Goseck and Count Dietrich II of Katlenburg.