If The Sun Also Rises serves as a fictional ode to Hemingway's feelings about the First World War then why did he and his circle of expatriates feel unwilling or unable to return home?

After WWI, many young Americans left their native country, bitter over the war and seeking adventure. A circle of artistic expatriates -- among them Hemingway, F. Scott Fitzgerald, Sherwood Anderson, Ezra Pound, and Pablo Picasso -- formed in Paris under Stein's guidance and shared their revolutionary ideas on art. While they helped define Modernist techniques in literature and painting, the Americans, in particular, catalogued the social upheaval in their homeland. While reeling from a huge blow to their innocence, Americans (at least the white middle- and upper-class) drifted irresponsibly through the prosperous era now known as the Roaring 20s. Hemingway and Fitzgerald employed their keen social observation in writing The Sun Also Rises and The Great Gatsby, respectively, widely considered the two masterpieces of Lost Generation fiction. The novels are remarkably similar: a somewhat indistinct young man narrates a story of unrequited desire for an untouchable woman in a hedonistic social environment. The major difference is that in The Sun Also Rises, it is the narrator whose desire is unrequited, and because of a physical impairment, whereas in Fitzgerald's work, Gatsby (not the narrator) cannot have his love interest for other reasons.