2 cents
As far as I'm aware when opposing armies fought, at the time of Viking and Norman conquests, it was still very much a melee, rather than disciplined line formation fighting. That suggests that armies could have many fighters who excelled in hand to hand combat. I don't know if that's true. I don't know when fighting in disciplined line formation began after the Romans, only that it apparently ceased in 1916. (?)
In either case,weren't battles about attrition, with the side with the most fighters still standing at the end being the victor?
Trivia: Sun Tzu avoided fighting. He claimed that wars were won or lost before any fighting took place. His goal was always maximum gain for minimum loss.
“The greatest victory is that which requires no battle.”
― Sun Tzu,
The Art of War