About the end of the 8th century both the Shetlands and Orkneys suffered from the depredations of Norse vikings, or pirates, until Harold Haarfager annexed the islands to Norway in 875.
It is bounded on the east by the North Atlantic, the Norwegian and Greenland Seas-Jan Mayen, Iceland, the Faeroe Islands and the Shetlands being the only lands between it and Norway.
It has been found more convenient to take as northern boundaries the narrowest part of the straits near the Arctic circle, Bering Strait on the Pacific side, and on the Atlantic side the narrowest part of Davis Strait, and of Denmark Strait, then the shortest line from Iceland to the Faeroes, thence to the most northerly island of the Shetlands and thence to Cape Statland in Norway.
Papa Stronsay (16) commemorates in its name, as others of both the Orkneys and Shetlands do, the labours of the Celtic papae, or missionaries, who preached the Christian gospel before the arrival of the Northmen.
Norse pirates having made the islands the headquarters of their buccaneering expeditions indifferently against their own Norway and the coasts and isles of Scotland; Harold Haarfager ("Fair Hair") subdued the rovers in 875 and both the Orkneys and Shetlands to Norway.