The Duchy of Brunswick-Lüneburg was formed out of the possessions of senior branch of the House of Brunswick. The House of Brunswick originated from the Italian House of Este. This family acquired the inheritance of the Guelph family by marriage — around the year 1000 — of Azzo II with Kunigunde of Altdorf, daughter of Welf II. Again important possessions were gained in (Lower) Saxony by the marriage of Henry the Black to Wulfhilde of Saxony (d 1126), daughter of the last member of the House of Billung, who had been Dukes of Saxony for five generations. They were made Dukes of Brunswick-Lüneburg in 1235. In 1269 the house of Brunswick-Lüneburg divided into the branches of Lüneburg and Brunswick (later Brunswick-Wolfenbüttel, the later Duchy of Brunswick). In 1432 the Principality of Calenberg, the later Electorate of Hanover, split from Brunswick(-Wolfenbüttel), and in 1705 acquired the territory of Lüneburg.