According to the
Royal Frankish Annals and the
Saxon Poet, the
Austreleudi (Eastphalians) under
Hessi gave hostages and swore loyalty to
Charlemagne at the river
Oker in 775. Hessi later converted to Christianity and was made a
count. The bishoprics of
Halberstadt and
Hildesheim were established in Saxony east of the Oker in 804 and 815 respectively. The medieval Duchy of Saxony was divided between the districts of Eastphalia (
Ostfalahi), Westphalia, Nordalbingia, and
Angria. The Eastphalian territory at the
Harz mountain range was the hereditary lands of
Henry the Fowler, the first Saxon duke to become
King of the Romans in 919, and his descendants of the
Ottonian dynasty. They left several
Romanesque abbeys and castles, a cultural landscape that today encompasses three
World Heritage Sites with the medieval town of
Goslar and
Quedlinburg, as well as
St. Mary's Cathedral and
St. Michael's Church at
Hildesheim. As the Eastphalian territory bordered on the lands of the
Polabian Slavs, both along (
Drevani) and beyond the Elbe and Saale rivers (
Limes Sorabicus), it became the starting point of the German
Ostsiedlung ("settling of the East") started by the invasions of King Henry and continued by the Saxon
margraves. Sometime after 965, king ad emperor
Otto I (936-973) entrusted the defense of northeastern Eastphalian regions, later known as
Altmark (meaning:
the old march) to count
Thiadricus (
Dietrich of Haldensleben), placing him in charge over the pacification of neighboring Slavic tribes, such as
Redarians and
Hevellians. After the
Welf duke Henry the Lion was placed under
Imperial ban in 1180, Eastphalia was increasingly subdivided into smaller states, foremost the Welf
Duchy of Brunswick-Lüneburg and the counties of
Anhalt,
Wernigerode and
Blankenburg as well as the Imperial city of Goslar, but also the ecclesiastical territories of the
Archbishopric of Magdeburg, the prince-bishoprics of
Hildesheim and
Halberstadt and
Quedlinburg Abbey. The Saxon tradition was perpetuated by the
Ascanian dukes of
Saxe-Wittenberg, who secured for themselves the
electoral dignity and later established the
Electorate of Saxony on the upper Elbe. ==Subdivisions==