I've been reading more about how soldiers will often aim to scare off enemies than outright kill them, as it is human nature to avoid killing each other. I learned of an anecdote where a line of 500 riflemen (revolutionary war period if I recall correctly) fired at a long cloth representing a line of enemies, scoring several hundred hits; however during battle their hit rate was in low single digit percentage.
Many modern soldiers involved in firefights will say that while they are trained to aim center mass, they rarely aim and fire their weapons there.
I'm wondering if ancient soldiers were more desensitized to the act of killing since it was more up close and personal, i.e. hand to hand combat.
If anyone has any insight into this or reading material on the topic I'd love to see it. Thanks!
Edit: Since archers fired in an arc with many others, could that have taken away from the personal connection to the killing itself? My thought here is that since with rifles you aim directly and it is clear when your shot did the kill, making it more "personal".
You might be interested in this previous post I wrote on the accuracy of smoothbore muskets. There were a number of experiments like this during the late 18th-early 19th centuries and accuracy in combat certainly did tend to be dramatically lower than what soldiers could achieve on the practice range. However the theory that many soldiers would "intentionally" aim to miss seems to be a modern one and is pretty controversial. Period sources instead will attribute the difference to factors such as excitement, mistakes made while loading or aiming, fear, stress, noise, and smoke.
It's worth noting that in the past century the average number of bullets expended in combat per enemy casualty doesn't seem to have improved much, with estimates frequently reaching the 10s of thousands, however modern weapons can also fire much more rapidly than muzzle loading muskets could.
You may be interested in this wonderful writeup on ancient Greek warefare by one of the moderators here.
https://www.reddit.com/r/AskHistorians/comments/48pumt/did_the_people_in_the_front_lines_of_ancient/