One thing I read today might contribute to this, I found it rather interesting. I was reading about Black Death, and ended reading also about the Great Famine

One thing I read today might contribute to this, I found it rather interesting. I was reading about Black Death, and ended reading also about the Great Famine that happened a bit before it, and the two are attributed to be part of the reason why Chivalrious warfare ended, before these two events, professional soldiers (knights for example) usually died in training accidents than in actual battle... But the deep changes caused by these two events, caused among other things, the start of a more destructive kind of warfare, where instead of winning by making the enemy retreat, you would win by completely destroying the enemy forces. I suspect in some periods of history there was less PTSD because war was just less violent. After Black Death, and increasing since, we got closer and closer to the idea of total war, that ended happening for real in the World Wars.