Myke Cole writes a great and heartfelt article about combat and killing, and how most fantasy novels, though steeped in violence, don't convey the experience and the consequences:
One doesn’t have to be a veteran brawler to write a great fight scene.
But I do feel like the end result of fighting, namely, killing, isn’t often treated in a way that resonates with me. I can count on one hand the number of writers who get it right. Joe Abercrombie springs to mind as one of them, a tiny band of authors, and I do not count myself among them, who evoke the consequences of killing in a way that feels authentic.
[...T]here is one thing in particular that I think fantasy writers miss, and I want to dial in on that here.
Killing is a chain.
It's good, so read it all here: http://mykecole.com/blog/2014/03/on-killing