Final answer:
Hrafn thought he won because he struck a severe blow to Gunnlaugur, while Gunnlaugur thought he won because he managed to wound Hrafn as well.
Step-by-step explanation:
Hrafn thought he had won the duel in Iceland because he struck Gunnlaugur a severe blow to the head, causing him to fall to the ground and lose his weapon. Hrafn believed that this meant he had defeated Gunnlaugur and claimed victory.
Gunnlaugur, on the other hand, thought he had won because although he was wounded and unable to continue the fight, he managed to wound Hrafn as well. In Viking culture, achieving a draw or inflicting equal harm on one's opponent was considered a victory.
Learn more about duel in Iceland