I've gone on record many times saying that the west fights wars like no other culture in existence. While history has proven without question that our methods of warfighting are superior to all others, what is not often pointed out is how idiosyncratic they can be. No place is this quirkiness thrown into a starker light than our conception of the special status of a "prisoner of war."
These perceptions originate with the ancient Greeks. No culture up to that time had ever attempted to compose its armies of relatively free and equal citizen-soldiers. Unique in all the world, a Greek soldier had the expectation of protection under law, and the ability to speak his mind without fear of arbitrary reprisal. By enshrining these beliefs in the core of their culture Greek soldiers ceased to be merely chattel and acquired an intrinsic value, became more than simply a shrieking rabble whose individuals were patently expendable simply because the general didn't like the way they smelled that morning.
The next innovation would be brought by Christianity. By instilling a core doctrine of universal love, by preaching that all human beings are intrinsically valuable, and by firmly placing the concept of a universal, immutable law to which even despots and emperors must obey at its center, Christianity allowed the definition of "value" to be spread from the soldier to the serf. Certainly these concepts would be eclipsed and ignored in brutal ways, but they were never completely forgotten, and, in this particular combination, they were powerful and unique.
Unfortunately the inheritors of the Greek traditions, the Romans, like every other culture ever to contact the near east, became seduced by the concept of god-emperor. As they adopted more and more of the trappings of absolute power the very beliefs that made them the rulers of the known world gradually corroded into dust. What the barbarians eventually destroyed in the forth century of the common era would have been unrecognizable to a senator of the third century BC, and in no small part even to Augustus himself four centuries before the collapse.
The Germanic tribesmen who swept away imperial rule in the west may have been primitive and illiterate, but they brought with them powerful and new beliefs in the supremacy and sanctity of the warrior. It was still possible, even acceptable, for a Visigoth or Merovingian chieftain to lop the head off a soldier due to incompetence, cowardice, or even insubordination, but that chieftain was then expected to compensate the soldier's family a fixed amount of gold for his fit of temper.
What gradually developed in the time between the fall of the empire and the rise of the nation-state was a unique culture that not only saw the value of the combatant at war, but also of that same combatant in surrender. By distributing land and rights to a comparatively large number of noblemen and welding this to innovative methods of finance, feudalism imbued the elite warrior with a certain kind of "equity" that made his life as valuable to his enemy as it did to his lord.
Unique in all the world this culture evolved an entire economy based on the concept of ransom. Anywhere else on the planet a knight or soldier unhorsed or disarmed was seen as merely an inconveniently (and therefore ever-so-temporarily) wriggling piece of meat. In the West, however, that selfsame helpless enemy was not seen as an impediment, but rather as an opportunity, a poker chip wrapped in a tin can valuable only as long as he lived.
Knock a knight off his horse and you were entitled to all his stuff, but if you stayed calm enough not to kill him you could offer it all back, for a price. More than one noble family got its start in the chaos of the tourney field when a freeborn boy got a lucky blow in on an unsuspecting knight, and conversely more than one literal king's ransom had to be paid because an effete nobleman decided the coincidence of birth outweighed the strength of desperation.
Elaborate rules were drawn up for ransoms, not just on the battlefield but in tournaments as well. Mercy for a surrendered foe gradually stopped being a novelty and more and more was expected of a "civilized" gentleman. Rituals were developed for the recognition of individual surrender, rules were created for what constituted proper and improper treatment, and an entire infrastructure was built up almost exclusively for the exchange of prisoners for gold.
It's important to emphasize that this culture of chivalry existed nowhere else in the world. Islam may hold itself up as the guiding light of religious tolerance, but the emirs and sultans thought nothing of slaughtering thousands of disarmed foes like livestock in a single day. In the Americas a victorious warrior could often expect a drunken, colorful, but most of all extremely short and sharp victory celebration, and in Asia a head could be separated from a set of shoulders literally at the twitch of an eye.
Of course, a peasant didn't fare all that much better in the West. After all, what good is ransoming someone who's worth less than the land they till? Mercy toward a common foot soldier developed relatively late in the west, as the concept of personal liberty and universal justice took hold in the enlightenment of the seventeenth century. Even then it was more a redrawing of the boundaries of who could benefit from chivalry rather than a transformation of the concept itself. The sense of "fair play" and "fair game" at its core survived. When Europe boiled out of its rapidly industrializing homeland for the final time in the sixteenth century, it took with it not only the unique concept of warfare as a form of cultural extermination, but also that there could actually be rules to govern this horrific idea.
The more traditional, but no less sophisticated, agrarian societies of the rest of the world were confronted with a juggernaught of unprecedented lethality and efficiency which paradoxically demanded nearly inconceivable mercies to it combatants. It was beyond surreal to such cultures that these incredibly vicious and always victorious white men expected to be spared simply because they threw down their arms. Even worse, to slaughter these devils as proscribed by tradition lead to even worse predations rained down on your head. Not only were these maniacs undefeatable, they were insane.
In a strange sort of way it's like football (US rules) or cricket... you simply have to grow up with it for it to make sense. A westerner will have no trouble understanding the distinction between a bomber crew dropping firebombs on a city being "fair game" and that selfsame crew in parachutes suddenly "off limits". That the only difference between the former and the latter is now the victims of the bombing have an extra set of mouths to feed is immaterial to a westerner. The city was, after all, being defended with anti-aircraft artillery. To be called subhuman for shooting the perpetrators of a terrifying attack simply because they're floating within easy reach beggars the imagination of most other cultures.
The rest of the world did eventually catch on, deciding that this bizarre fascination for the west's defeated and dishonored could be used against them, a chink in our armor they have been studiously prying on ever since. What they do not understand is our concern for captives is actually one of the strengths of the way we fight wars. Time and again returned prisoners insist the primary source of their strength in captivity was the knowledge that their government and their countrymen were doing everything in their power to get them out safely. Our soldiers take calculated instead of suicidal risks because of this fact. Finally, by caring humanely for our own captives we ensure that the next generation is raised with a father to teach instead of a legend to avenge.
Because you see for us, at root, to do anything less would be barbaric.