Despite conventional wisdom on the topic of Fitzgerald and war – that because he was not a combatant, war therefore had little effect on him and his work – it is important to understand the ways in which he thought World War I had fundamentally and irretrievably changed Western civilization. Fitzgerald did not write combat literature that emphasizes the naturalistic aspects of modern war, as his old friend Hemingway did most notably in A Farewell to Arms (1929), but he did write one of the most engaging war novels, Tender Is the Night, about the aftermath of World War I. In this essay, I shall explore the ways in which Tender functions as a war novel, as opposed to combat fiction, differences that can best be understood when the novel is contrasted with other World War I fiction, such as Henry Barbusse's Under Fire: The Story of a Squad. Moreover, the broader social implications of war in Tender, such as Dick Diver's war neuroses, are easier to contextualize in relation to such works as Stendhal's The Charterhouse of Parma and William Makepeace Thackeray's Vanity Fair, novels about war during the Napoleonic period. I shall argue that, while in these nineteenth-century novels war is not shown as having had a lasting psychological effect on society, in Tender Fitzgerald clearly shows the lasting psychological impact of World War I.