The Czechs in Bohemia were less fortunate. Boleslas Chrobry, i.e. the Brave, of Poland (992-1025), had aspired to rule over an united kingdom of the Northern Slavs, but had to be content with the independence of his own Polish kingdom. Bretislas of Bohemia (1037-55) had a similar ambition; but he could not shake off the German yoke, and his bishopric of Prague remained a suffragan of the Metropolitan of Mainz. [Sidenote: Adalbert of Bremen.] North of Bohemia, in the country lying between the Baltic, the Elbe, and the Oder, Otto had established a series of marks or border-lands in which he had built towns, introduced German colonists, and founded bishoprics which he had grouped round a new Metropolitan at Magdeburg. Here for nearly a century and a half the House of Billung did much to keep under the surging tide of paganism. It was the ambitions of Adalbert, Archbishop of Bremen (1043-72), which for a time caused a serious heathen reaction in this quarter. He was the rival of Hanno of Koln for influence at the Court during Henry IV's minority. As the most northern German Metropolitan he aspired to set up a patriarchate in Northern Europe. He met with considerable success in Scandinavia. [Sidenote: Scandinavia.] The Christianisation of Denmark had been completed under Cnut, who also ruled over England (1014-35). Norway was also being rapidly converted; but the forcible methods of King Olaf, who afterwards became the patron saint of his country, roused discontent. Cnut added Norway to his dominions, and was anxious to make his realm ecclesiastically independent. He established three bishoprics in Denmark, but did not get his own metropolitan, and his empire fell asunder at his death. Adalbert made a close alliance with Swein of Denmark, and thus kept the Danish Church dependent. Harold Hardrada struggled against Adalbert's attempts to assert his power in Norway. Sweden had accepted Christianity under Olaf Stotkonung, i.e. the Lap-King, who died in 1024. But until towards the end of the eleventh century heathenism continued to maintain itself, and the difficulties of the Christian party were considerably increased by the assertive policy of Bremen. Adalbert's schemes were wide-reaching. He sent bishops to the Orkneys, to Iceland, and even to Greenland, of which the last two lands had been converted by missionaries from Norway and ultimately became subject to the Metropolitan of Norway. [Sidenote: Wends.]