The Abodrites (Obodrites) were one of the many Slavic tribal confederations that in the late sixth or early seventh century settled in Germany east of the river Elbe. From the ninth to the thirteenth centuries they became the target of intense missionary and later crusading activity from the West.
The Abodrite confederation was composed of three major tribes: Wagrians, Polabians, and Eastern Abodrites. Nominally they had a king (Lat. dux or rex in the sources), but power largely resided in the hands of princes (Lat. reguli or principes), who were the heads of noble families. In the ninth century the Abodrites were politically oriented toward Denmark, a connection reflected in marriage bonds between the Danish and Abodrite ruling families. In the tenth century, however, the Holy Roman Emperors gained some ascendancy over the Abodrites, and in 967 Emperor Otto I (936-973) established a missionary bishopric at Oldenburg in Abodrite territory as part of the archbishopric of Hamburg-Bremen.
Although some of the Abodrite kings nominally accepted Christianity, the new religion made only little headway among the Abodrites for the next 200 years or so, and there were several pagan uprisings from the late tenth century until the early twelfth century; on a number of occasions churches were burned, priests murdered, and Christian ruling families expelled by their pagan foes. Renewed efforts in the 1120s by Archbishop Adalbero of Bremen (1123-1148) to Christianize the Abodrites also failed, and soon the princes forbade all missionary activities in their lands. Then in 1147, during the Second Crusade, Saxons and Danes took part in a campaign against the Abodrites and other Slavic peoples, an enterprise approved by Bernard of Clairvaux and sanctioned by Pope Eugenius III. Henry the Lion, duke of Saxony, was in overall command of the Saxon crusaders. Even though he and his followers agreed to leave the Abodrite lands after a crushing defeat of the Danish crusader army, the crusade of 1147 marks a turning point in relations between the West and the Slavs: from that point the Abodrite lands were a target area for Saxon expansion and intense Christianization.
In 1159 King Valdemar I of Denmark (1157-1182) complained to Henry the Lion that the Slavs kept raiding the coasts of his realm, and so in 1160 Henry attacked the Abodrites once again, devastating parts of their territories with support from Valdemar. The Abodrite princes became vassals of the Saxon duke and nominally accepted Christianity. However, it was only after the Danish conquest of the island of Rügen in 1168 that the princes seem to have succeeded in extending Christianity throughout their lands by founding churches and monasteries. Now largely Christianized, and becoming increasingly Germanized, the Abodrite lands were integrated into the German kingdom as the duchy of Mecklenburg.