Fighting is about winning but survival is about... surviving, and anything goes. Survival is dirty, in the sense that if you think it's going to be a fight you will only realize he had a knife when the damn thing is already between your ribs or whichever side you momentarily forgot to leave less protected. Survival is something where you will get injured, bleeding and body parts disjoint very quickly; most often both of you do, and running like hell is often the best way to survive: in a war that might not always be an option, though.
Of course, that is, assuming it started as a one-on-one situation and ended as one, too.