If a grizzly bear attacks you, play dead. If it’s a black bear, try to scare it off. If you get caught by a polar bear, you may as well fight because you have nothing to lose.
Unfortunately, neither playing dead nor fighting back works as well against polar bears as against their smaller relatives. They’re often more interested in eating you than in neutralizing you as a threat, so playing dead might just make their job easier. Fighting back is pretty useless, too, but if you find yourself rolling around the tundra with a one-ton polar bear, you don’t have much to lose. As with other bears, try to injure its nose or eyes, and steer clear of those big, swinging paws. A single strike can kill a person.