After the peace, Frederick’s main occupation lay in Germany. During the Emperor’s Italian troubles the power of Henry the Lion had gone on increasing. In the north in particular, Henry had renewed the ancient policy of extending the German race at the expense of the Slavs. Using his Saxon duchy as the basis of his operations, he completed the Germanisation of the lands between the Elbe, Baltic, and Oder, that, despite the work of the Ottos, and Lothair and Albert the Bear, were still largely Slavonic and heathen. So solid was his power, that disasters in Italy, such as in the days of the Ottos, had led to a Slavonic reaction in the north-east, had no influence in retarding the march of German conquest. Before long, the vastness of Henry’s resources and the stability of his policy threw the exploits of Albert the Bear into the shade. In alliance with the young Valdemar I. of Denmark, Henry carried to a completion the long process of the conquest of the half-heathen tribes beyond the Elbe, and grudged his reluctant ally a share in the spoils of war. The warlike Abotrites were at last subdued and forced to profess Christianity, and the fortress and bishopric of Schwerin was established by Henry in their midst, along with numerous colonies of Saxons and Flemish settlers. [Sidenote: Henry the Lion and the Marks.] Henry was as great a founder of towns as Otto the Great. Lübeck, founded in 1143 by his dependant, Count Adolf of Holstein, and the first German town on the Baltic, owed its existence to his energy. The bishoprics of Mecklenburg and Pomerania claim him as their founder. Cistercian and Premonstratensian missionaries crushed out the last remnants of heathenism, and trade followed strong rule. In 1168 Henry married Matilda, the daughter of Henry of Anjou, an alliance that established a warm and permanent connection between the Guelfic house and the English throne.
[Sidenote: Henry the Lion and his duchies.]
Henry the Lion sought to rule within his duchies with the same autocratic power with which he governed his border conquests. The local nobles and prelates saw in his policy a design against their franchises, and combined to offer him a vigorous resistance. Albert the Bear, who had never lost hope of regaining Saxony, opposed him even in the Marks. In 1166 the princes of Saxony, headed by Rainald of Dassel and the Archbishop of Bremen, went to open war against Henry, but the personal intervention of the Emperor restored peace in the Diet of Würzburg. The Lion’s northern allies were equally alarmed at his triumphs; and Valdemar of Denmark, irritated by his requiring a share in the recent Danish conquest of Rügen, became his enemy, but was soon obliged to crave his forgiveness, and Valdemar’s son and successor, Canute VI., married Henry’s daughter Gertrude. In 1170 the death of the restless Margrave Albert relieved Henry from the most dangerous of his opponents. His position was now so strong that he was able, between 1170 and 1172, to go on pilgrimage to the Holy Land, where he was received with great honour, and whence he brought back many relics, which he enshrined in the stately churches at Brunswick of which he was the founder. Though shorn of the East Mark by the creation of the new duchy of Austria, Henry was still able to exercise almost as great an influence on the Germanisation of the south-west as on the same process in the north-east. It was the age of German colonisation, when, from the overpeopled lands of the Netherlands and old Saxony, adventurers sought a fresh home in the lands newly won to civilisation. German colonists in Meissen and in the lands ruled by Czech and Magyar, owed their position to Henry. In Bavaria itself he was the founder of the city of Munich.