Kingdom of Norway (872–1397)

The term Norwegian Realm (Old Norse: *Noregsveldi, Bokmål: Norgesveldet, Nynorsk: Noregsveldet) and Old Kingdom of Norway refer to the Kingdom of Norway's peak of power at the 13th century after a long period of civil war before 1240. The kingdom was a loosely unified nation including the territory of modern-day Norway, modern-day Swedish territory of Jämtland, Herjedalen, Ranrike (Bohuslän) and Idre and Särna, as well as Norway's overseas possessions which had been settled by Norwegian seafarers for centuries before being annexed or incorporated into the kingdom as 'tax territories'. To the North, Norway also bordered extensive tax territories on the mainland. Norway, whose expansionism starts from the very foundation of the Kingdom in 872, reached the peak of its power in the years between 1240 and 1319.

At the peak of Norwegian expansion before the civil war (1130–1240), Sigurd I led the Norwegian Crusade (1107–1110). The crusaders won battles in Lisbon and the Balearic Islands. In the Siege of Sidon they fought alongside Baldwin I and Ordelafo Faliero, and the siege resulted in an expansion of the Kingdom of Jerusalem. Leif Erikson, an Icelander of Norwegian origin and official hirdman of King Olaf I of Norway, explored America 500 years before Columbus. Adam of Bremen wrote about the new lands in "Gesta Hammaburgensis ecclesiae pontificum" (1076) when meeting Sweyn I of Denmark, but no other sources indicate that this knowledge went farther into Europe than Bremen, Germany. The Kingdom of Norway was the second European country after England to enforce a unified code of law to be applied for the whole country, called Magnus Lagabøtes landslov (1274).

The secular power was at its strongest at the end of King Haakon Haakonsson's reign in 1263. An important element of the period was the ecclesiastical supremacy of the archdiocese of Nidaros from 1152. There are no reliable sources for when Jämtland was placed under the archbishop of Uppsala. Uppsala was established later, and was the third metropolitan diocese in Scandinavia after Lund and Nidaros. The church participated in a political process both before and during the Kalmar Union that aimed at Swedish side, to establish a position for Sweden in Jämtland. This area had been a borderland in relation to the Swedish kingdom, and probably in some sort of alliance with Trøndelag, just as with Hålogaland.

A unified realm was initiated by King Harald I Fairhair in the 9th century. His efforts in unifying the petty kingdoms of Norway resulted in the first known Norwegian central government. The country, however, soon fragmented, and was again collected into one entity in the first half of the 11th century. Norway has been a monarchy since Fairhair, passing through several eras.