This blog post stands alone, but is also designed to add depth to other posts in this Combat Realism series, starting from the very first one, which discusses the human surrender reflex.
I've heard it reported that human beings only have one natural, instinctive fear that all of us share without learning it. That would be the fear of very loud noises, such as thunder or explosions.
That isn't quite true, though. Human beings instinctively feel a sense of intimidation by someone who much taller than they are. And while infants at times seem to show no fear of falling, the terror of falling from heights is very common in adult human beings, whether they've ever had a bad fall or not. As is the fear of drowning. An adult who has never been taught to swim feels instinctive terror of being submersed in water, in almost every case.
So there are fears other than loud noises that are for all practical purposes universal, if not fully so 100%. Especially significant to the discussion of combat is, most human beings have a strong, natural aversion to killing another human. In addition, most members of our species find the thought of another human trying to kill them especially terrifying.
Killing another human being is hardest when its face-to-face and when it involves stabbing into another person's body. The first part of this involves the fact we humans read one another's emotions primarily through facial cues. For almost all people, witnessing another human suffer causes at least a weak empathetic response. Like laughter or coughing becoming contagious, the normal human psyche feels a reflection of another human being's suffering.
If people are too far away for their faces to be seen, as in a combatant firing artillery or dropping bombs, killing bears a lesser psychological effect--unless the recipients of bombing or shelling are seen up close later. Hard close combat causes psychological injury to human beings--submarine crews or bomber squadrons in WWII, who were in fact in as much or more danger as infantrymen, usually were less traumatized by their experiences. Note that while snipers fire from far off, their use of optics brings their targets pretty close.
Note also how this factor relates to the "chase" instinct mentioned in part one of this series. When an enemy turns and runs away, it is easier to kill them by stabbing them in the back than it is to stab them while facing them. This suggests the old cultural prohibition against shooting a man in the back being an act of cowardice was not only there because it is safer to shoot someone who can't see you. It is also psychologically easier to shoot someone without looking him in the eye--which means for some people, they'd be more likely to pull the trigger at people with their backs turned. An act our ancestors judged to be villainous.
The "stabbing into another body" part from above perhaps is a particular issue because it strikes people instinctively as being interlinked with sexual intimacy and therefore especially wrong (and for certain criminally disturbed minds, especially exciting). It happens to be the case that stabbing into the body is a very effective way to kill people. Yet human beings have often gravitated towards weapons that swing in order to slice or smash as killing weapons. It's worth considering that one of the reasons why a person might use a sword to slash or hack has nothing to do with weapon effectiveness, but rather with the psychological factor of avoiding putting a penetrative wound in another person, up close and personal.
Related to the revulsion against stabbing into other human beings is the terror the thought of having someone else do that to us inspires. Humans are certainly afraid of being bombed or shelled, largely because the terrible noises the explosions make, but we'll take our lives into our hands in automobiles in reckless ways without much fear at all. It's different when someone is deliberately trying to kill you. And while the idea that another human would drop a bomb on you or target you with a sniper rifle certainly can inspire fear, I'd wager most people are more afraid of an enemy who will stab them to death with a knife up close.
So let's put all these factors mentioned into play in a medieval battlefield scenario. A high tower or wall is not only an effective defense because gravity helps you fire down on an enemy from up high--it is terrifying to climb a high wall for most human beings because of the fear of falling. And the castle moat may not in fact be so deep that a man at arms in armor couldn't wade through it. But he's unlikely to want to try, for fear of drowning. The archer on the castle wall has an easier job than the infantryman on the battle line, not just because he is in less relative danger, but because he can shoot enemies beyond the distance where he can see their faces. Infantry in the field break and run from charging cavalry lancers because men on horseback are taller, the horses make a thundering noise. and the thought that "those men coming at us are going to pierce us through with lances." When the infantry turn and run, it is not only easier to stab them in the back from the point of view of it being safer, it becomes more of an anonymous act. A line of musketeers fire back at the cavalry and they break as a group and gallop away, not just because the musket balls can penetrate their armor, but because of the tremendous noise the firing guns make.
Of course not every human being reacts to these situations in the same way. Some people feel very little fear of heights, for example. And the purpose of military training is to make certain actions a matter of rote memory, so they can be performed under any circumstances (other blog posts in this series explore factors that make both killing and facing death easier). But a story writer must account for human fears in battle portrayals. The effects are far-reaching and touch many aspects a person would not immediately notice are dictated by instinctual human fears.
Note this blog post, while explaining human fears and reactions, is addressed to speculative fiction writers. You have the opportunity to play with mythological creatures, with aliens, and demihumans like Elves and Dwarves. Of course the cyborg or robot creature who has no fears at all has been done over and over in science fiction and will always have a place. Yet what I suggest writers should do is give non-humans on your fictional battlefields instinctual fears other than what humans have, with perhaps some overlap or interrelation with human fears. Then consider how differing fears might affect the actions of a fictional army. For example, an alien species might routinely face a predator with an orange body and as a result have an instinctive fear of orange. Once an enemy figured that out, all armor would be routinely colored orange--just as many soldiers in our world once wore tall hats or high plumes to take advantage of the fact that most human beings find someone taller than them intimidating (tall hats disappeared when weapon effectiveness from a distance made their payoff in intimidation not worth how much easier a target a soldier using such a hat became).
The next post in this series will cover physical wounds instead of psychological ones, what really causes death in the real world. And what should cause battlefield deaths in worlds of speculative fiction...