Meanwhile among the Wends Gottschalk's son revived his father's authority and contact with German civilisation; but after 1131 the Wendish kingdom fell to pieces, and from that moment we can mark the steady advance of German power to the Oder. The Billung line of Saxon dukes had become extinct in 1106, and Henry V had given the ducal name to Lothair, who succeeded him as Emperor, and who as Duke aimed at building up a strong dominion in north-eastern Germany. As Emperor he took up the civilising rôle of Otto the Great and encouraged the Germanisation of the Slavs. The actual work was done by his chief adviser Norbert, whom he had almost forced to become Archbishop of Magdeburg. He acted in conjunction with Albert the Bear, a descendant in the female line of the Billung dukes and Margrave of the Northmark, who himself founded bishoprics among his immediate neighbours the Wiltzes. Albert's soldiers prepared the way for Norbert's Premonstratensian canons, and bishoprics were founded with so little regard for division of territory, even in Poland and Pomerania, that both Gnesen and Lund found themselves for a time subordinated to Magdeburg. Two names are especially associated with the conversion of the Wends. In 1121, under the patronage of Lothair who was not yet Emperor, Vicelin began his work among the Wagrians, and in 1149 he became their Bishop with his see at Oldenburg. He died in 1154. It was under the auspices of Henry the Lion, now Duke of Saxony, that Berno preached to the Obotrites, converting the Wendish Prince and becoming Bishop of Mecklenburg. The gradual advance of German colonisation had weakened the Wendish resistance and prepared the way for this restoration of Christianity. Henry the Lion finished the work. In alliance with Waldemar II of Denmark he repeated with greater completeness the work of founding bishoprics, establishing houses of Premonstratensians, whose missionary activity was now shared by the Cistercians, building towns and introducing colonists, until the whole country between the Northmark and the Baltic was included in his Saxon duchy. [Sidenote: Pomerania.]