I'm looking at poets too. :) But as it's for a US history seminar, they'll all be American poets - which is kind of unfortunate, as the US IIRC didn't have any standout war poets, whereas the UK has Owen, Sassoon, Rupert Brooks...

I think Tolkien's Dead Marshes, at least, show some clear WWI influence: the images of soldiers floating up from underwater. And the Shire is in a sense an attempt to regain the world that WWI destroyed.