In Italy, independent city states grew affluent on eastern maritime trade. These were in particular the thalassocracies of Pisa, Amalfi, Genoa and Venice. From the mid-tenth to the mid-11th centuries, the Scandinavian kingdoms were unified and Christianized, resulting in an end of Viking raids, and greater involvement in European politics. King Cnut of Denmark ruled over both England and Norway. After Cnut's death in 1035, England and Norway were lost, and with the defeat of Valdemar II in 1227, Danish predominance in the region came to an end. Meanwhile, Norway extended its Atlantic possessions, ranging from Greenland to the Isle of Man, while Sweden, under Birger Jarl, built up a power-base in the Baltic Sea. However, the Norwegian influence started to decline already in the same period, marked by the Treaty of Perth of 1266. Also, civil wars raged in Norway between 1130 and 1240. By the time of the High Middle Ages, the Carolingian Empire had been divided and replaced by separate successor kingdoms called France and Germany, although not with their modern boundaries. Germany was under the banner of the Holy Roman Empire, which reached its high-water mark of unity and political power. During the successful reign of King David IV of Georgia (1089–1125), Kingdom of Georgia grew in strength and expelled the Seljuk Empire from its lands. David's decisive victory in the Battle of Didgori (1121) against the Seljuk Turks, as a result of which Georgia recaptured its lost capital Tbilisi, marked the beginning of the Georgian Golden Age. David's granddaughter Queen Tamar continued the upward rise, successfully neutralizing internal opposition and embarking on an energetic foreign policy aided by further decline of the hostile Seljuk Turks. Relying on a powerful military élite, Tamar was able to build on the successes of her predecessors to consolidate an empire which dominated vast lands spanning from present-day southern Russia on the Black Sea to the Caspian Sea. Georgia remained a leading regional power until its collapse under the Mongol attacks within two decades after Tamar's death. In the High Middle Ages, the Kingdom of Hungary (founded in 1000), became one of the most powerful medieval states in central Europe and Western Europe. King Saint Stephen I of Hungary introduced Christianity to the region; he was remembered by the contemporary chroniclers as a very religious monarch, with wide knowledge in Latin grammar, strict with his own people but kind to the foreigners.