Early in the year 995 Olaf proceeded to Norway, and arrived at Throndhjem just when the peasants had risen against Earl Haakon. They made him their chief, and when the earl was dead, and his sons had fled, Olaf Trygvason became king of Norway.
Olaf Trygvason was twenty-seven years old when he came to Norway. At a general Thing at Throndhjem the people elected him king of all Norway, as Harald the Fairhaired had been, and in return he promised to enforce law and justice. The following spring and summer Olaf travelled through the whole country, to the southernmost part of Viken, and everywhere he was hailed as king, even by the chiefs in the Uplands and in Viken, who, during the reign of Earl Haakon, had at least nominally acknowledged the suzerainty of the Danish king. In the Uplands the petty kings, who were descendants of Harald the Fairhaired, were allowed to retain their possessions on the old conditions.
Olaf had decided, before he left England, to introduce Christianity in Norway, and he found it advisable to commence this work in Viken, where he had many of his relatives and warmest friends. Here was the rich and influential Lodin, who, some time before, had married Olaf's mother Astrid. His mother's brothers and two brothers-in-law of Olaf were also mighty people in that part of the country. Another reason for starting the work here was that a good many had already adopted the Christian faith under the influence of missionaries from Germany and Denmark. During his stay in Viken, Olaf called his relatives together and informed them of his intention to convert the whole of Norway to the Christian faith. He would accomplish that, he said, or die in the attempt. But he promised to make his relatives great and mighty men if they would support him with all their power. This they agreed to do, and as the most powerful men among the people had now acceded to King Olaf's request, the others followed their example, and all the inhabitants of the east part of Viken allowed themselves to be baptized. Greater opposition was met in the north part of Viken (around "Folden"), where Christianity had not had so many former adherents. But Olaf would tolerate no opposition; those who opposed him he punished severely, killing some, mutilating others, and driving some into banishment. During that summer (996) and the following winter all Viken was made Christian.