I would suggest the opening and closing sensory images. The bitter irony they produce, despite the narrator's calm, quiet, distanced tone, is bitingly painful and thus perfectly representative of the spirit of the narrative;
We are satisfied and at peace. [...] I am very quiet. Let the months and years come, they can take nothing from me, they can take nothing more.
The power of these images,especially when juxtaposed, is confirmed in the Dedication of the novel:
This book is neither an accusation nor a confession, and least of all an adventure, for death is not an adventure to those who stand face to face with it. It will try simply to tell of a generation of men who, even though they may have escaped shells, were destroyed by the war.