Speaker
The speaker is the “he” of the title: he is the killer. Interestingly, the narrative is framed with quotation marks, suggesting that the speaker is actually saying the words out loud. Since the opening stanza and the closing stanza both refer to taverns or pubs (“ancient inn” and “bar”) the conventional interpretation is that the poem is a snatch of conversation taking place in a bar dominated at this point by the speaker’s monologue. He is a soldier who returned from the Boer War in South Africa relating the event of killing an enemy on the battlefield.
The Man He Killed
The man whom the speaker kills on the battlefield is first described as someone who, had the meeting taken place under any other circumstance, might have been someone the speaker sat down to enjoy a drink with. But they do meet on the battlefield and the result is the death of one at the hands of the other, but it could just as easily have gone the other way because the two men shot at each other simultaneously. The speaker muses with some wistful melancholy that this is the nature of war: you wind up killing a stranger who if you met in a bar you’d treat to a round.