Here's the thing. This entire poem is written in the first person. We're hearing about this battlefield death from the mouth of the man who actually made that death happen.
Which raises the question: why isn't the title "The Man I Killed"? Great question, Shmoopers. We were wondering just that. So we came up with a little theory. Hear us out.
We are not meant to be on board with this speaker. We're not meant to relate to him, feel empathy towards him, or even approve of him. Thomas Hardy certainly doesn't, and we shouldn't either.
Why? Because this is an anti-war poem. Because Hardy wants to show us just how senseless war really is. And he does so by giving voice to someone who clearly can't quite find his voice—someone who stumbles over his words and is insensitive enough to call war "curious," someone who can't quite acknowledge the fact that he ended another man's life.
But Hardy doesn't want you confusing this speaker with, you know, him. So he takes a step back in the title and calls it "The Man He Killed." Hardy's off the hook for being a clueless jerk (like our speaker kind of is), and already we're looking at this poem with a cool, calm, and critical eye.
This theory's a bit less controversial, but no less viable. You could absolutely argue that this poem is called "The Man He Killed" to remind us of the fact that it's a narrative and dramatic poem. In fact, it's a dramatic monologue, which means that this poem is being spoken to us from the perspective of a particular character whom Hardy has invented.
What that tells us is that we're going to get a story, a moment of drama, rather than a personal confession of someone's thoughts and feelings. This speaker isn't pouring his heart out. He's talking to a person, or a group of people. That means he's probably not saying everything. We don't know the whole story. Calling the poem "The Man He Killed," reminds us that we're eavesdropping on a dramatic moment—not snooping on the thoughts and feelings inside a speaker's mind.