I mean to some extent the native tribes of the area have hunted and killed polar bears with prehistoric technology. To answer your question, yes I believe someone wielding a true two-handed Viking styled broadsword that was well crafted could take the bears head off or something to that effect. But the odd would still be stacked in the bears favor heavily.I read stories of 19th century Mountain Men and Native American indians and others defeating large bears (Black, Brown/Grizzly) with large daggers and knives. How realistic is that and could the same be done today or would the person most likely take severe damage that leads to death or hospitalization? Also, could a trained person who has a large enough blade defeat a polar bear in hand to hand combat if it was necessary or there is no way?