Dogmax suggests "take us inside the foxhole."
One way to do that is to make this second person instead of third person.
Instead of being about "him/his" etc. make it about "you." Sing it directly to the soldier.
Also, you limit the generality of this by mentioning "trench warfare." It's about every war (the're ALL "Hell" aren't they) until you mention that, then it's just about the first world war. I think that's a mistake.
Wonderful imagery, but I think it can get more personal, and better.