The Story of Norway by Hjalmar Hjorth Boysen

On his return to Norway, Olaf Haroldsson found his elder brother Magnus, who had already been acknowledged as king before his father's death, in possession of the government. After some negotiations it was agreed that the two brothers should divide the kingdom between them -- Magnus taking the larger portion toward the north and west, and Olaf contenting himself with Viken. If this division was founded upon the equal allodial rights of the brothers, it was obviously unfair. But Olaf, being averse to quarrelling, accepted it, as far as we know, without protest.

The campaign to England had largely exhausted the resources of the country; and Sweyn Estridsson of Denmark thought that the opportunity was now favorable for avenging the wrongs which he had suffered at the hands of King Harold. The brothers then made levy in mass from all the country, but Sweyn succeeded in engaging Olaf with his division of the fleet, off the coast of Halland (1067), before Magnus had joined him. The battle must have been indecisive; for both sides claimed a victory. It is, however, probable that Olaf suffered the more, as he was the first to propose peace. Magnus had, in the meanwhile, come, and their allied fleets were, in all probability, equal or superior to Sweyn's. At all events, Sweyn had suddenly lost the desire to prosecute the war; and a peace was made at Konghelle (1068), at which assurances of friendship and good-will were exchanged. Olaf is said to have borne his part in the negotiations with a firmness and intrepidity which inspired Sweyn with respect.