Why? Because...
At first, Hardy's "The Man He Killed" came off as non-chalant to me. The man didn't seem to care that he just shot down a fellow that he (if in a different situation) might have befriended. He seemed to be a drone, programmed to find "the enemy" (no questions asked) and take them out.
Then I reread this quote (line 9-10) "I shot him dead because-/ because he was my foe" (372). This quote stopped me. The narrator stopped mid-sentece/mid-thought here, trying to find some justification (other than because he was the enemy), perhaps fully realizing his actions and that this man is not just "the enemy", but another man (like him) who enlisted for what he believes in or just for a job.
And now he is dead. Yet the narrator still doesn't seem that impacted. "Curious war is!" he says as if its just a new fact he learned about wild animals.
I thought the speaker was actually so impacted by the event that he ended up muddling through his thoughts, trying to find absolution of his guilt. I think that when he said "Curious war is!", the tone is actually somewhat sarcastic. He feels guilt, but knows that he had to do it.
I also thought he seemed to be rather nonchallant about the whole ordeal. It is easier to not allow yourself to dwell on a traumatic experience. I thought he seemed numb and distant almost as if it was an out of body experience.