Christianity was first introduced into Denmark in the sixth and seventh centuries through raids on Ireland, commerce with Holland, and the story of the "white Christ." Willibrord was the first missionary.[250:1] When he was expelled from Friesland in 700 he went to Denmark, where he was received with favour by King Yngrin, organised a church, and bought thirty boys to be educated as missionaries. St. Sebaldus,[250:2] the son of a Danish king, was a product of this early missionary effort. Charles the Great ruled part of Denmark, carried on extensive trade with the people, located churches in Holstein and at Hamburg, and planned to convert all the Danes.[250:3] Louis the Pious, appealed to by King Harold Klak[250:4] to settle a family feud, sent Archbishop Ebo of Rheims and Bishop Halitgar of Cambray to Denmark in 822. Ebo made several journeys, later preached extensively, won many converts, baptised them, and built a church at Welnau. When, in 826, King Harold Klak fled to the Emperor for aid, he, together with his whole family and train, was converted and baptised at Ingelheim. Upon returning, the King took with him Ansgar, a Frank born at Amiens (800), who had been early trained as a missionary teacher and preacher, and who was to win the title of "Apostle of the North." He laboured in Denmark with some success, but in 829 was expelled, when Harold Klak was once more driven out, and went to Sweden until he was elected bishop of Hamburg in 831 with all Scandinavia as his see. In 846, Bremen was united to Hamburg and Ansgar was made archbishop. He soon succeeded in planting Christianity and with it monasticism in Denmark. His successor, Archbishop Rimbert (865-888), continued the spread of Christianity undisturbed; and his successors Adalgar (888-909), Unni (909-936), and Adaldag (936-988), had a comparatively clear field. The last of these saw the consecration of four native bishops, an increase in the possessions of the Church, and an organised struggle against heathenism. When the Danes made a conquest of England, the results were seen in the conversion of King Swen, a zealous worker for the Church, and his son Canute (1019-1035), who completed his father's work with the aid of English missionaries. So strong was the Church in Denmark by the twelfth century that a separate archbishop was appointed. The supremacy of the Roman Church was recognised.