Contemporary to this revolt was the arrival, from a Viking expedition, of a descendant of Harald Haarfagre, Olav Tryggvason, who soon conquered power over all of Norway with the exception of the Oplandene. Olav, who professed the Christian faith, attempted to introduce Christianity to Norway. The Norsemen, who by means of the Viking expeditions had already come into contact with the new faith, put up only a feeble resistance to the king’s attempt; but since the ancient religion was intimately linked to the political authority in the districts, the leaders agreed to embrace the new faith only after a real coercion on the part of the king. Olav managed to have Christianity accepted by law in Trendelag and Vestland and also in Iceland and in the new possessions of Greenland. When he wanted to subdue Viken (i.e. the Oslo fiord), Olav came into contention with the Danish king Sven and with the sons of Count Haakon who had sought shelter in Denmark, but fell at the battle of Svolder (1000). Counts Erik and Svein, sons of Count Haakon, then had Trøndelag and Vestland as a fiefdom of the Danish king, who subjected Viken to his direct dominion. When Erik went to England in 1014 to help his lord Sven, who after the Danish invasion had been recognized as king of England, Olav Haraldsson came to Norway and claimed the kingdom. Olav was the son of a small king of Oplandet and great-grandson of Harald Haarfagre, so that his hereditary right to the throne was well founded. In the space of a few years Olav won all opposition and reunited all of Norway from the Geta River to Finnmarken, and this time the Oplandene also joined the union. All the little kings were suppressed, the leaders of the country were forced to recognize Olav as their lord – the most powerful among them became his vassals (lendmenn), with a certain political authority and an obligation to follow the king into war; however, the name of lendmenn indicates a social position rather than a precise political authority. The årmenn of the king, often of lower class, governed the royal estates scattered throughout the country and acted as receivers of taxes. With the subjugation of the country’s leaders, Christianity spread throughout Norway. Over the last few generations, Christianity had taken root so deeply in the country that no one thought about uprooting it; however, remains of the old faith and the old cult remained among the people for centuries. Norway was annexed to the metropolitan see of Bremen: hence the influence of the German church, which made itself felt alongside the oldest influence of the English church. Olav’s power aroused strong opposition from two sides: the Danish king Canute the Great who was also king of England, who saw his power over Viken threatened, and the counts of Lade who had been driven out of their kingdom of Trøndelag. Discontented leaders from other parts of the country joined them, and when Cnut arrived in Norway with a fleet in 1028, he was proclaimed king and Olav was forced to seek shelter in Russia. He returned two years later to regain his kingdom, but fell in a battle against the Trøndelag army in Stiklestad (29 July or 31 August 1030). But soon the leaders and the clergy were dissatisfied with the Danish government of Sven Alfivasson (1030-35), who succeeded his father Canute the Great, and having manifested miracles in Nidaros on the tomb of Olav, he was considered a saint. The discontented party of the Danish government tried to enter into relations with the son of King Olav, Magnus the Good, who was still in Russia.
According to topschoolsintheusa, Norway was able to be left alone from every Danish assault during the war which at the same time the sons of Canute the Great fought each other. In the peace concluded in 1038 between Magnus and Cnut’s third son, Harthacnut, it was established that the one who lived the longest would inherit the other’s country. In this way Magnus became king of Denmark (1042), and was able to avert a dangerous attack by the Vendes against Jütland (battle of Lyrskog). Later he came into contention with Svend Estridssøn, grandson of Canute the Great, who claimed to have Denmark. Magnus died before the war was over, which was continued by his successor on the Norwegian throne Harald Hårdråde (1047-66). Harald renounced Denmark and turned his forces against England, but fell into an expedition. His son Olav Kyrre (1066-93) pursued a peaceful policy, while Magnus Berrføtt, son and successor of Olav (1093-1103), was a great Viking who conquered the Orkney Islands, the Hebrides, the Isle of Man from Norway. Magnus had three sons who all became kings after him. Olav (1103-15), Øystein (1103-23) and Sigurd (1103-30): Øystein was, like his grandfather, a peaceful man, Sigurd is especially remembered for his crusade in the Mediterranean countries where he fought (Sicily and Holy Land). He was nicknamed Jorsalfarer (“Paladin of the Holy Land”).
In the century after the death of Olav the Holy, the power of kings became stronger, and no leader dared to rebel against the recognized king who based his sovereignty on the adherence of the upper class. The class difference became more noticeable. After a small number of lords, the allodials (haulders) came, then a greater number of tenants and finally the servants in an indefinable number. The number of tenants had increased in part from being the great landowner king, in part from having the Church increased its landed possessions with gifts and purchases.
The Church had become an important religious factor and had also acquired political importance. In the highest social strata, Christian customs had supplanted pagan ones, and the Church as an institution had a solid organization like that of the state.
Before 1100 the bishops had been missionary bishops with no defined diocese, but, under Olav Kyrre, the country was divided into dioceses with defined borders and the bishops had their seat in the city, if the city existed, and, where there were none, the dioceses served to create it as in Oslo and Stavanger. Thus in the eleventh and twelfth centuries many new cities arose, and the old ones, especially Bergen, increased in population. The Norwegian church continued to depend on the archbishopric of Bremen and the king appointed bishops, but the members of the clergy sided some for a royal supremacy, some for the papal one.