The narrator wakes up and walks out of his tent only to find three dead bodies and he realizes how terrible war actually is. They begin to relate the three deceased to the father, son, and the Holy Spirit.
The narrator relates the three dead people to people from the bible. The father is supposedly "God", the young man is supposedly the "Son", and the little baby is the "Holy Spirit."
The author speaks in a very dark tone and the entire poem is aimed around the fact that war is a terrible thing and it affects all people from all walks of life.
The narrator goes from waking up like any normal day, to seeing three dead bodies and it completely changes how his day begins.
The title makes you curious as to what the narrator is seeing and it also hints at the fact that the narrator isn't seeing something bright or happy because gray and dim usually isn't good.
The theme is that war is a very terrible thing and it is not good for anyone or anything except killing people.