Orkneyar was a Viking sea kingdom which existed in northern Scotland from 875 to 1231. The Norwegians named the islands of Orkney the Orkneyjar ("seal islands"), and, during the Unification of Norway, several enemies of King Harald Fairhair of Norway fled to Orkneyar and established a Viking base. In 875, King Harald forcibly annexed Orkneyar and the Faroe Islands and appointed jarls of Orkney, and, by 878, Orkneyar included Caithness (named "headland of the Catti" by the Norse), Sutherland (Suðrland), and Ross-shire. Rognvald Eysteinsson was the first Norse Jarl of Orkneyar, establishing a line of semi-independent jarls which would reign until 1231. King Eric Bloodaxe often used Orkneyar as a base until his death in battle in 954, and, in 995, King Olav Tryggvason forced Sigurd the Stout and the Orcadians to adopt Christianity after threatening them with fire and steel if they refused baptism. In the early 11th century, Thorfinn the Mighty ruled over a small maritime empire stretching from Dublin to Shetland, and, from 1100, the Jarls of Orkney paid homage to Norway for Orkney and to Scotland for Caithness. In 1231, Jon Haraldsson's murder in Thurso ended Rognvald's unbroken line of Norse earls, and Orkney fell under the direct rule of Norway. In 1468, King Christian I of Denmark pledged Orkney as security against the payment of his daughter Margaret of Denmark's dowry to King James III of Scotland. As the money was never paid, Scotland annexed Orkney in 1472. By 2015, 25% of Orcadians were descended from the Norwegian invaders of the 9th century AD.