He disliked the work and took solace in evening classes in painting and drawing at Birkbeck College. The poem begins with the speaker introducing the fact that a new day is dawning.
He observes that the trenches and the other demarcations of war that separate the English soldiers from their "enemies" matter little to the rat, which will perhaps cross no-man's-land to continue its feast on German corpses.
So that humanist flower has been gradually dropping flower. He imagines the image of a poppy, and its melting from the arms of all the soldiers. But hark! It was drawn to the narrator as he moved to touch the poppy. It immediately sets the devastated scene for us and prepares the way for the scattering of dust in the last line.
He speaks aloud, stating that if the Germans knew the rat had touched an English hand, or visa versa, it would surely be shot. He continues on to describe how the rat surpasses all men in its strengths.
The notion of being "chanced" for life is wonderful, and the mayhem of the exploding shell is summoned this time with simple, almost Biblical imagery. It seems you inwardly grin as you pass Strong eyes, fine limbs, haughty athletes, Less chanced than you for life, Bonds to the whims of murder, Sprawled in the bowels of the earth, The torn fields of France.