Albert was the oldest surviving son of the first Brunswick duke
Otto the Child and his wife,
Matilda of Brandenburg. When his father died in 1252, he took over the rule of the duchy. In 1267 the duchy was divided between Albert and his younger brother
John. Albert's rule was initially troubled by several armed conflicts as the Welf dukes still had to cope with the followers of the extinct
Hohenstaufen dynasty within their dominions. In 1260/61 Albert's troops fought against the Danish duke
Eric I of Schleswig on behalf of Queen
Margaret Sambiria and her minor son King
Eric V of Denmark. In 1263 the duke quite luckless interfered in the
War of the Thuringian Succession to support the claims raised by his mother-in-law
Sophie of Brabant. On 31 May 1267, the brothers agreed to divide the Welf lands, which happened in 1269. Albert partitioned the territory while John obtained the right to choose his part. He took the northern half including the region of
Lüneburg,
Celle and the city of
Hanover, while Albert received the southern part around the cities of
Brunswick and
Wolfenbüttel, stretching from the area around the
Calenberg hill to the town of
Helmstedt, the
Harz mountain range, and
Göttingen. The Brunswick residence itself was to remain common property of the brothers. Albert then concentrated on the development of his hereditary lands. During the Imperial
interregnum, he sided with the rising Bohemian king
Ottokar II until his final defeat in the 1278
Battle on the Marchfeld. When his brother John died in 1277, he took over the guardianship for his minor nephew
Otto II of Brunswick-Lüneburg. Albert died on 15 August 1279 and is buried at
Brunswick Cathedral. He was succeeded by his elder three sons, the younger three joined the Church. ==Marriage and children==