For Esmé with Love and Squalor
The villain here is World War II itself – or perhaps the concept of war in general. War is depicted as a destructive force that does nothing but alienate people, both from themselves and others. It's associated with a deep sense of loss for all of the characters: Esmé loses her father, and is afraid of losing the narrator, as well; Sergeant X loses his sense of self, and even the insensitive Clay fears that he lost his sanity at moments, and can't quite explain this fact. The war taints everything it touches, and the struggle of the story is the fight to get over this life-changing event.