The Christian kingdoms of Denmark and Sweden were also eager for expansion on the eastern shores of the Baltic. In 1218 Albert asked King Valdemar II of Denmark for assistance, but Valdemar instead arranged a deal with the Order. The king was victorious in the Battle of Lindanise in Revelia in 1219, to which the origin of the Flag of Denmark is attributed. He subsequently founded the fortress Castrum Danorum, which was unsuccessfully besieged by the Estonians in 1220 and 1223. King John I of Sweden tried to establish a Swedish presence in the province of Wiek, but his troops were defeated by the Oeselians in the Battle of Lihula in 1220. Revelia, Harrien, and Vironia, the whole of northern Estonia, fell to Danish control.