According to the Res gestae saxonicae by tenth century chronicler Widukind of Corvey, the Saxons had arrived from Britannia at the coast of Land Hadeln in the Elbe-Weser Triangle, called by the Merovingian rulers of Francia to support the conquest of Thuringian kingdom, a seeming reversal of the English origin myth where Saxon tribes from the region, under the leadership of legendary brothers Hengist and Horsa, invade post-Roman Britannia (see Anglo-Saxon settlement of Britain).

The Saxons devastated the Frankish stronghold at Eresburg; their leader (Herzog) Widukind refused to appear at the 777 diet at Paderborn, retired to Nordalbingia and afterwards led several uprisings against the occupants, avenged by Charlemagne at the Massacre of Verden in 782.

Afterwards, Saxony was ruled by Carolingian officials, e.g. Wala of Corbie (d. 836), a grandson of Charles Martel and cousin of the emperor, who in 811 fixed the Treaty of Heiligen with King Hemming of Denmark, defining the northern border of the Empire along the Eider River.

Among the installed dukes were already nobles of Saxon descent, like Wala's successor Count Ekbert, husband of Saint Ida of Herzfeld, a close relative of Charlemagne.

Ida of Herzfeld may have been an ancestor of the Saxon count Liudolf (d. 866), who married Oda of Billung and ruled over a large territory along the Leine river in Eastphalia, where he and Bishop Altfrid of Hildesheim founded Gandersheim Abbey in 852.

Liudolf became the progenitor of the Saxon ducal, royal and imperial Ottonian dynasty; nevertheless his descendance, especially his affiliation with late Duke Widukind, has not been conclusively established.

Subdued only a few decades earlier, the Saxons rose to one of the leading tribes in East Francia; it is however uncertain if the Ottonians already held the ducal title in the ninth century.

Liudolf's elder son Bruno (Brun), progenitor of the Brunswick cadet branch of the Brunonen, was killed in a battle with invading Vikings under Godfrid in 880.

He was succeeded by his younger brother Otto the Illustrious (d. 912), mentioned as dux in the contemporary annals of Hersfeld Abbey, which, however, seems to have been denied by the Frankish rulers.

His position was strong enough to wed Hedwiga of the Babenberg, daughter of mighty Duke Henry of Franconia, princeps militiae of King Charles the Fat.

As all of Hedwiga's brothers were killed in the Franconian Babenberg feud with the rivalling Conradines, Otto was able to adopt the strong position of his father-in-law and to evolve the united Saxon duchy under his rule.

Henry was able to integrate the Swabian, Bavarian and Lotharingian duchies into the imperial federation, vital to handle the continuous attacks by Hungarian forces, whereby the Saxon troops about 928/929 occupied large territories in the east settled by Polabian Slavs.

Henry's eastern campaigns to Brandenburg and Meissen, the establishment of Saxon marches as well as the surrender of Duke Wenceslaus of Bohemia marked the beginning of the German eastward expansion (Ostsiedlung).

During his reign, Henry massively supported to the development of the cities in his dominion, such as Brunswick, Lüneburg and Lübeck, a policy ultimately contributing to the movement of the House of Welf from its homelands in southern Germany to the north.

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.