'War doesn’t determine who is right, it decides who is left', said Bertrand Russell. But the process of overcoming human aversion to killing has gone on throughout human history. In combat, soldiers find it hard to kill at close range. Analysis of various battles showed that the majority of soldiers never fired their guns. There’s something that holds people back, making us incapable of pulling the trigger. Those who would not fire did not run or hide—in many cases, they were willing to risk greater danger to rescue comrades, get ammunition, or run messages. Military historians have discovered that stabbing a fellow human being is even harder than shooting at close range.
The observation of low firing rates till World War II resulted in the US army, and subsequently other armies, initiating certain changes in their training methods designed to enable killing in the modern soldier. It initiated an era of psychological warfare, conducted not upon the enemy, but upon one’s own troops. The philosopher-psychologist Peter Marin says the lack of discussion about the topic is "a massive unconscious cover-up" in which society hides itself from the true nature of combat.
Training techniques of modern soldiers try to develop a reflexive "quick shoot" ability. If men reflect too deeply upon the enemy's common humanity, then they risk being unable to proceed with the task of killing the enemy. Instead of shooting at bull's-eye targets, the modern soldier spends many hours with full combat gear shooting at man-shaped targets at varying ranges. The soldier must instantly aim and shoot at the target(s). Soldiers are highly rewarded and recognised for success in this skill of accurately "engaging" the targets — a standard euphemism for "kill."
There is the development of boot-camp glorification of killing. It was almost unheard of in World War I, rare in World War II, increasingly present in Korea, and thoroughly institutionalized in Vietnam. For eg., Vietnam recruits were immersed in boot camps that exalted not only a sense of brotherhood, but also the most brutal violence, forcing the men to scream ‘KILL! KILL! KILL!’ until they were hoarse. The language used in training camps to describe the joys of killing people helps desensitize soldiers to the suffering of an enemy.
An article by an Army major (Pierson, 1999) in Military Review advised commanders to identify the less than 4% of troops who are psycho or sociopathic because they are the ones who can be counted on to willingly kill. (“[A] controlled psychopath is an asset on the killing fields”.) The resistance to killing can be psychologically modified. It’s easier to kill when you aren’t targeting an identified individual — so throwing a grenade into a group is easier than shooting at one person. The intensity of the trauma suffered by an individual who kills another is proportional to the distance between the two.
Most of the time, wartime killing is something you do from far away so that you don't see the enemy. The development of the rifle greatly increased the distance and speed of killing. From the mid-nineteenth century on, technological innovations made it possible to kill ever-increasing numbers of non-combatants at greater distances with heavy cannon, far beyond the direct perception of the artillerists who manned them and who hardly noticed the suffering they inflicted. This long-distance killing peaked with the firebombings of Tokyo and the atom bombs dropped on Hiroshima and Nagasaki.
Most people are killed by someone who pushed a button, dropped a bomb, or planted a mine. The mechanical distance provided by the unreality of killing through a TV screen, a thermal sight, a sniper sight, or some other kind of mechanical buffer makes killing easier. You could even describe the whole evolution of military technology as a process in which the psychological distance between the combatants is progressively increased. A very modern way of increasing the ease of killing is what the US military does today using armed drones. You can also drug your soldiers to dull their natural empathy and antipathy towards violence.
Killing becomes easier when guilt is diffused. It allows the shooter to think that even if he hadn’t done it, it still would have happened. This idea is used in modern execution technology in the US. Lethal injection machines used in prison executions come with a dual control system — two syringes, each filled with a lethal dose, two separate delivery systems, two buttons pressed simultaneously by two different people. Then a random binary generator would secretly determine which syringe was emptied into a bucket and which into a human. And then the record would be erased, allowing each person to think, “Hey, I may not even have given him any drug.”
Aside from long-range weapons, armies also pursue means to increase psychological distance to the enemy. If you can dehumanise the other – say, by portraying them as vermin – it makes it easier to treat the other as if they are indeed inhuman. If depersonalization is stretched into hatred, the restraints on human behaviour in war are easily swept aside. Without the creation of abstract images of the enemy, and without the depersonalization of the enemy during training, battle would become impossible to sustain.
But increasing the 'kill-rate' comes with a cost. Many soldiers returned after the Vietnam war with post-traumatic stress disorder (PTSD). This had been framed as a result of the sheer terror of being under attack, of someone trying to kill you and those around you. But psychologists eventually realized that this was a simplistic explanation. During World War II there were low rates of psychiatric breakdowns among sailors and medics — people who were just as endangered as infantrymen but killed either impersonally or not at all. Militaries train soldiers to override their inhibitions against killing, and something inside them had died, too.
Consider drone pilots — soldiers who sit in the United States, directing drones on the other side of the planet. They are not in danger. Yet their rates of PTSD are just as high as those of soldiers actually “in” war. Why? Drone pilots kill from thousands of miles away using imaging technology of extraordinary quality. A target is identified, and a drone operator might watch him for weeks. He would watch the target coming and going, eating dinner, taking a nap on his deck, playing with his kids. And then comes the command to fire. No personal danger, killing is a day job for them. Yet they suffer from PTSD.
The study of killing gives us good reason to feel optimistic about human nature, for it reveals that almost all of us are overwhelmingly reluctant to kill a member of our own species under just about any circumstance. Armies have had to develop sophisticated methods for overcoming our innate aversion to killing, It challenges the popular myth that human beings are “natural-born killers.” Popular culture has done much to perpetuate the myth of easy killing..