Please don’t ask me to remember where I found this, it was several years ago while I was plundering a trove of stuff from a military surplus store. I read in some War College military thinking piece that in WWI, WWII and Korea, the “hit” factor was way low. In other words, 100 soldiers firing at human targets only produced some 15 to 20% hits.
It was noted they trained on paper targets.
In Vietnam, the “hit” factor improved dramatically. I forget the percentage.
It was noted that the military switched to human profile targets.
Their conclusion was that most humans have a natural aversion to actually shooting another person, and that by using human outlines, they were able to desensitize the troops considerably.
I always thought that it was an interesting observation, and one that should probably be considered in any kind of crisis training.
This sounds a lot like research done by Dave Grossman for his book On Killing.