The speaker of "The Soldier," is the… soldier. Need we say more? Oh. We do? Well, then. There are a few things to note about this guy, since he's pretty revealing in the way he goes about this poem. Let's take them one at a time, shall we?
When you start a poem with "If I should die," then you're already confronting a cold, hard truth that most people would rather not think about. As a solider, though, the speaker is thrust face-to-face with his own mortality, and so this poem is his way of working through that imminent possibility. (Historically, for Brooke, that possibility became a sad reality when he went off to war and died of infection not long after this poem was written.) So we feel that we must give the speaker props for dealing with reality, rather than ignoring it.
Of course, the way that the speaker deals with the threat of death is hardly realistic. He imagines a kind of heaven that will be just the like home, full of the same thoughts, sights, sounds, and even dreams of his native land. Now, you could say that this makes our speaker a real patriot (more on that soon), but you could also make the case that he's sort of deluding himself. Sure, it'd be nice to imagine heaven as a place exactly like your favorite place, but think about that for a second. Isn't doing so just imagining that you're current experiences will go on forever, despite death? Isn't this just an elaborate form of denial, then?
Another way to read the speaker's "English heaven," though, is just to see it as a natural extension of his love of country. We mean, dude is big into England. He celebrates his upbringing there, promises to claim more land for it in the war, and portrays heaven as nothing more than the same pubs and fishmongers that he knows from High Street. In other words, he's saying that England will go on forever—both in terms of earthly conquest, and in terms of heavenly immortality.
This patriotism, then, is part of what ultimately blinds the speaker to the very real, impending horror of World War I. While we have to cut Brooke some slack for not being able to tell what was to come when he wrote "The Soldier," his speaker is a great example of the kind of naïve, overly-romantic, and jingoistic thinking that could send millions of people into armed conflict against each other.