Note that the cause of Jake's agony was an airplane that crashed. The early Moderns believed that industrialization, with its laborsaving and communication-enhancing devices, was wholly good, and that an increase in the mechanization of life could only make living easier, happier, better. The combatants in World War I discovered that the opposite was true: mass-produced, mechanized tools of destruction — tanks, planes, submarines, mines and machine guns, not to mention deadly mustard gas — made life on earth more terrible than ever before. Moreover, in this war, a soldier might kill and be killed without ever seeing the enemy. The Great War was the first truly anonymous war; in this conflict, the individual was entirely dispensable.
Thus, Jake is not merely a casualty of war in general, like the characters of Homer, Tolstoy, and others before him. Bayonets were still in use at this time; Hemingway could have made Jake a victim of one. Instead, Jake is injured specifically by the Great War's modern aspect — by modernity itself, one might say. Hemingway expanded upon this theme in A Farewell to Arms, the hero of which is famously wounded by an enemy bomb while eating a bowl of spaghetti.
As a result, we have a love story in which it is clear from the start that the lovers will never be together. At least, they will never be happy together. In the vast majority of stories ever told, there is at least some possibility that the protagonist, or main character, will get what he or she wants by the end. In The Sun Also Rises, it becomes quickly evident that Jake will not — cannot — "get" Brett. How, then, will Hemingway retain our interest in the goings-on he describes? Because we know the conclusion of the story at its outset, why read on? (The short answer: Hemingway's characterization of Jake, Brett, and the rest, who are portrayed with such originality and believability that they seem like real people to us.)
