There are these Medieval penitential codes from after the Battle of Hastings, essentially a list of penances to give people who served in war. They give penances somebody is supposed to do if they killed somebody in war or if they injured somebody in war. They're supposed to go and confess and then they get a penance. If you killed somebody, this is what you get. If you maimed somebody, this is what you get. If you're an archer and you have no idea if you killed somebody, but you probably could have, this is what you get. It's very detailed.

What's fascinating to me about that is it's not saying you fought in a bad war and therefore you must be punished. It's you fought in a war that we wanted you to fight in, that we needed you to fight in. And yet, having done what was required of you, what was honorable in that circumstance, now you also need to confess because you did evil. Because killing another human being made in the image of God is an evil thing. 

In a Veterans Day episode of the Another Life podcast, Phil Klay explains why he went to war and how it changed him.