When I reviewed Germline by T C McCarthy, I mentioned it reminded me of a scifi-ified version of a book I’d read years ago about the Vietnam War.
I came across that book today, and it is entitled “Fallen Angels” by Walter Dean Myers (which, ftr, I only bought in the first place because he had my last name).
I would heartily NOT recommend you read it if you are at all offended by foul language, as it is rife with it. But it is also a gritty story told from the perspective of someone who was living it every day.