>>12000
>In nearly all historical batlles prior to the age of Napoleon, the serf who looked down his spear or musket at the enemy saw another hapless serf very much like himself, and we can understand that he was not particularly inclined to kill his mirror image

It is more true for Napoleonic times and later. Until 17th century armies (at least in Europe) had much more professional/mercenary composition, and masses of poor serfs weren't active participants of most wars.

>And so it is that the great majority of close-combat killing in ancient history was not done by the mobs of serfs and peasants who formed the great mass of combatants. It was the elite, the nobility, who were the real killers in these battles, and they were enabled by, among other things, social distance.

This statement looks pretty strange. Amount of nobility that engaged in large battles weren't very large, often it is about 100-200 proper knights or something like this in large battles. They did heavy damage of course, but they couldn't do majority of close-combat killings.

Although he is right about some social distance thing. For example. knight-vs-knight conflict often ended with capturing and ransom scheme. Even in cross-religion wars there were many examples of this.