why are the french girls so important?

The sexual liaison across the canal at first appears to be a picaresque adventure of the kind frequently found in war stories; lusty young soldiers skirt authority while meeting up with exotic local women. But from the start, it seems doomed for failure. First, sex to the men cannot be a regular experience; war has made sure of that. Instead of getting new clothes to "compete" for the woman in the poster, they have to settle for a delousing.

Moreover, the women are French and, technically, their enemies. This immediate confusion (which does not seem to bother any of them at all) bleeds into an even greater ambiguity: the fusion of love and war. Love and war are frequently starkly contrasted in literature: love produces birth and other emotions of re-birth, while war produces death and its attendant mortal emotions. Paul hopes to separate love and war--he wants the brunette to deliver him from "war and terror and grossness, in order to awaken young and happy." However, the brunette is interested in Paul only if death is around the corner for him. When she learns he is going off on leave, he is no longer a "'pauvre garçon'" ("poor boy"), but simply another man. She is sold on the romantic notion of war, and love for her is possible only if Paul is an idealized, heroic soldier.