Especially in epic fantasy stories, human beings or demihumans like elves or dwarves are often portrayed as fighting to the death with a disregard to danger. Creating larger-than-life struggles is part of the appeal of epic literature, but an author should be aware of the behind-the-scenes psychology of that is normal to be able to grippingly and realistically portray the abnormal. Because it happens to be the case that people don't usually fight until the death--they fight until the surrender.
Many people are familiar with the so-called "Fight or Flight" response, a state of stimulation by danger that can alternatively cause a person to fight or to run away. But as documented in the book On Killing, when fighting members of their own species, not only human beings, but all social animals in creation have a third response--to surrender.
So wolves in a pack fighting to be the dominant member of the group--the "alpha"--don't usually fight until one is dead, but until one surrenders or yields dominance, which is signaled in a specific way by members of canine species, i.e. rolling on the back and exposing the belly. Male bighorn sheep joust, crashing their horns into one another for the right to mate, and on occasion seriously injure or kill one another, but don't usually. They usually go at it until one has had enough and quits the combat, "turning its tail" and moving away. And there are many other examples of this same sort of thing in the animal kingdom.
Human beings also have a surrender response as part of what I would call the "common operating software" that the human brain shares with many other living creatures. It's strongly influenced by culture, but humans usually signal quitting combat by raising up empty hands, showing themselves weaponless.
There are certain kinds of stimuli that trigger the surrender or flight response. For example, human beings tend to be intimidated by opponents who are taller. Which gives a reason why Greek, Roman, and other soldiers wore plumes on the top of their helmets--in addition to making someone easier to identify on the battlefield, such devices makes a warrior look taller. Looking taller didn't help a soldier fight better in the slightest, but it did increase the chances an enemy will feel the urge to run or surrender. (I believe ancient warriors comprehended instinctively that a helmet plume helped them fight, without having identified the reasons why.)
This understanding adds depth to the Biblical account of David and Goliath. Goliath's size not only made him more powerful, it made him more intimidating, which is not necessarily the same thing. Note that the Bible records that Saul had been in many battles and was a noted warrior long before Goliath challenged his army to send a champion to single combat. Yet in spite of his battle conditioning, Saul had no desire to face off against the Philistine giant himself. This went beyond a calculation of the threat the giant posed. It was instinctual--Saul seems to have found Goliath's height intimidating on a level deeper than reason--and David marked himself as a hero by his ability to overcome that instinct through his confidence in God.
Likewise early firearms, while they had the ability to do devastating damage, they were difficult to aim. So each had a practical range less than that of bows and crossbows of the same era. Not only was their range more limited, their rate of reload made them slower to operate that crossbows and much slower than bows. In terms of the ability to kill the enemy, bows or crossbows were not only more effective than the guns that replaced them, they were much more effective. But as a weapon of intimidation, firearms that roll like thunder and shoot flames like mythical beasts (the word "gun" is in fact short for "dragon") were intimidating to enemies in a way arrows could never dream of being. Early guns triggered panicked flight and openhanded surrender to such a degree that the gun was far more effective on the battlefield than bows and arrows, even though it was an inferior killing weapon in the beginning. In other words, it replaced the arrow as the distance weapon of choice primarily for psychological reasons. (Note this is not likewise true with cannons--cannons actually do more damage than the catapults they replaced).
It happens to be historically the case that soldiers have proven more likely to surrender rather than run when attacked from the front and behind simultaneously, i.e. when surrounded. When a route of escape is evident, there is a higher tendency for an intimidated army to run. Running triggers an instinctual response in opposing forces to chase after those fleeing the battlefield (like a wolf chases prey or an angry, territorial bull chases intruders on his terrain). Many warriors in ancient and medieval battles were killed after they psychologically broke and were in the process of running away. Ancient Roman armies employed cavalry primarily for hunting down and killing enemies fleeing from the battlefield.
So the clash of two armies on a battlefield, with both on the line against one another, often ended when one side perceived they would lose and morale broke. And often, especially in ancient and medieval times, far more people were killed on the battlefield after an army broke and ran than before, during what we would consider the normal phase of combat, army facing army.
Roman soldiers showed that disciplined footmen could hold off a cavalry attack even without using the pikes or spears used to break up cavalry charges in other armies. In truth, one of the reasons a cavalry charge was generally effective against foot soldiers came from the intimidation value of the charge itself, horses taller than men galloping their direction, their hooves making a roar like thunder. This often caused men on foot to break and run, or surrender.
As a general rule, troops who are poorly-trained are more likely to break. Troops that are highly disciplined and trained over and over again that surrender is a dishonor, surrender far less often, but still do. For example, while all Japanese troops in WWII believed giving in to an enemy was a grave dishonor and many refused to do so, a certain percentage still actually surrendered. As did even some of the Spartans fighting Athenians in the Peloponnesian War.
Soviet and German troops facing off against each other in WWII had a greater likelihood of fighting to the death than is normally the case, not only because of soldier discipline, but because of the high likelihood of troops being killed upon surrender by either side. A "take-no-prisoners" approach stiffens an enemy's resistance to giving up. But even so, soldiers under the strain of battle, even when they knew surrender would likely result in death, even if they were highly disciplined and had been ordered to fight to the bitter end even then still surrendered sometimes. That's how strong the surrender instinct is in a human being.
So, my fellow writers of fantasy and science fiction, in writing battles, it should happen sometimes that characters feel overwhelmed and surrender. Or run. Or if they don't, there needs to be something special about them that accounts for how they differ from what is in fact normal for human and nearly-human characters.
More about that on the next post covering this topic..