This is one question it is NOT okay to ask an Iraq war veteran. I know this, although I've never been exactly sure why. Best I could figure, it is because a) that is an intensely personal question, kind of like asking a stranger if they've ever had an abortion and b) because the answer is most likely "yes" and I should know that and they probably don't want to talk about the war.
Recently I have become acquainted with an army veteran of some thirteen years, multiple continents and numerous conflicts, including Afghanistan and Iraq. Thanks to his courage to look within and work hard, he has done a lot of healing from the inevitable psychic wounds of war, and thanks to his generosity in sharing, I am learning a lot from him.
I asked this vet why the question is so taboo. He explained that, during the conduct of war, you have to do things that, in our civilian society, are unacceptable. In peacetime, killing another human being is murder, and it's wrong. In war, it is the business of war. You do it because you have to, because they are the enemy. You kill people, you see people killed, you witness horrible destruction and suffering. It is what you do in combat, yet part of you whispers that if you're doing this, you must be a bad person. Sometimes, that part becomes convinced.
When you come home, you put those things, the events of war you have lived through, into a fragile compartment in your mind and protect it carefully.
If you try to answer the question, "Did you kill anyone?," all of a sudden you are forced to dig into your mind, expose that fragile compartment, and relive it. Whether you have personally killed anyone or not, you have been at war. You have participated in the conduct of combat and now you have to look at yourself in the mirror. You want to be a good person, you try to convince yourself that you are a good person, but when you see again the scenes of combat and feel the contamination of war's aftermath, you feel like a bad person. The conflict is excruciating.
I have never, thank goodness, asked a vet that question. Now I'm sure I never will.