when I was a kid I read of a Russian woman who was a sniper at Stalingrad.
She said the first man she killed left her with a a living nightmare. The German soldier’s head just blew apart, and all she could think of was the soldier’s mum, nursing that head, raising the man with loving care..all ended in a stupid moment.
But it was a job..it had to be done..the second didn’t have the same effect and within a week she didn’t feel anything.
It’s called being brutalised.
and it takes a while to become human again by all counts