Why Xavier wont kill we don't know!

What grabbed me into the book most so far was how Xavier didn't want to kill anyone when he is in a war. He is in the middle of a war what else would he do? Kill or be killed, that how it is in war. So why couldn't he kill anyone? I think he has to many morals and self control to be a savage and kill without even feeling for it. Personally I could only do that if i needed to protect my friends and family and that would be the only way id be able to kill. Which would be the situation in a war, I would protect my brothers in arms with my own life. Xavier has a weird way of thinking of this war Id say. Since he won't kill he shouldn't of even went to the war in the first place in my opinion anyways. It's a good book overall but the beginning is rather slow and confusing. A great book though!