Death. Lots and Lots of Death.
OK, so Wilfred Owen doesn't have a lock on death. After all, pretty much every major novelist and/or poet who's ever written anything has something to say on the subject. For Owen, however, death is the subject. In the tumult of battle, only one thing is certain: somebody will die. During the war, even the men who are alive act like zombies. If you've watched Sean of the Dead, you know that "zombie" is a another word for the walking dead. Given that Owen's poetry is all written during World War I, we're betting that he didn't have much opportunity to write about other material. Death may not be easy to face – but that, friends, is Owen's point.