Duchy of Saxony followed by Saxe-Lauenburg
House of Ascania
In 1269, 1272 and 1282 the co-ruling brothers John I and Albert II gradually divided their governing competences within the then three territorially unconnected Saxon areas (Hadeln, Lauenburg and Wittenberg), thus preparing a partition.
After John I had resigned in 1282 in favour of his three minor sons Eric I, John II and Albert III, followed by his death three years later, the three brothers and their uncle Albert II continued the joint rule in Saxony.
In 1288 Albert II applied at King Rudolph I for the enfeoffment of his son and heir Duke Rudolph I with the Palatinate of Saxony, which ensued a long lasting dispute with the eager clan of the House of Wettin. When the County of Brehna was reverted to the Empire after the extinction of its comital family the king enfeoffed Duke Rudolph. In 1290 Albert II gained the County of Brehna and in 1295 the County of Gommern for Saxony. King Wenceslaus II of Bohemia succeeded in bringing Albert II in favour of electing Adolf of Germany as new emperor: Albert II signed an elector pact on 29 November 1291 that he would vote the same as Wenceslaus. On 27 April 1292 Albert II, with his nephews still minor, wielded the Saxon electoral vote, electing Adolf of Germany.
The last document, mentioning the joint government of Albert II with his nephews as Saxon fellow dukes dates back to 1295. The definite partitioning of the Duchy of Saxony into Saxe-Lauenburg (German: Herzogtum Sachsen-Lauenburg), jointly ruled by the brothers Albert III, Eric I and John II and Saxe-Wittenberg (German: Herzogtum Sachsen-Wittenberg), ruled by Albert II took place before 20 September 1296. The Vierlande, Sadelbande (Land of Lauenburg), the Land of Ratzeburg, the Land of Darzing (today's Amt Neuhaus), and the Land of Hadeln are mentioned as the separate territory of the brothers. Albert II received Saxe-Wittenberg around the eponymous city and Belzig. Albert II thus became the founder of the Ascanian line of Saxe-Wittenberg.
Members of the Welf cadet branch House of Hanover later became prince-electors of Hanover (as of 1692/1708), kings of Great Britain, Ireland (both 1714), the United Kingdom (1801) and Hanover (1814).