Ostsiedlung
Under Carolingian rule

Charlemagne, ruler of the Carolingian Empire of Francia, which was founded by Franks (a Germanic people), under whom most of Western and Central continental Europe had been united during the 8th and 9th centuries, created numerous border territories, so called marches (German: Marken), where a substantial portion of the Ostsiedlung would later take place. The territories (from north to south):

This was the earliest recorded and planned "eastern policy" under Charlemagne, who wanted to protect the eastern border of the Frankish Empire, and also wanted to solidify his position in the east by declaring war on the Obotrites and Wilzes in the North, as well as on the Sorbs (east of Thuringia) and Czech tribal princes. However, since the goal wasn't to establish an ethnic and linguistic boundary between the Slavs and Germanic tribes, Slavic settlement continued in Thuringia and Northern Bavaria, with individual Slavs even making it to the Rhine Basin.

The tribes that populated these marches were generally unreliable allies of the Empire, and successor kings led numerous, yet not always successful, military campaigns to maintain their authority.

In 843, the Carolingian Empire was partitioned into three independent kingdoms as a result of dissent among Charlemagne's three grandsons over the continuation of the custom of partible inheritance or the introduction of primogeniture.
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