You don’t expect to find a hidden message in a book you first read when you were a teenager. Not when it’s part of the canon, analyzed for decades, with critical opinion on it a settled matter. But when I was asked to write an introduction to a new Vintage Classics edition of Ernest Hemingway’s A Farewell to Arms, that’s what I discovered: a secret, wrapped in an elegiac novel of love, war, and loss whose quasi-autobiographical overtones turned out to be both more and less than they seemed.

Anyone who knows the facts of Ernest Hemingway’s life has heard the story: how on the night of July 8, 1918, in the last summer of World War I, the 18-year-old Hemingway, an ambulance-driving lieutenant with the Italian Red Cross, was wounded in an Austrian mortar attack on Italian positions at Fossalta di Piave, in the Veneto. He’d been in Italy for little more than a month, and at Fossalta for only three weeks, when a shell exploded in the trench where he was delivering chocolate and cigarettes to the troops. “I died then,” he’d say later: “I felt my soul or something coming out of my body, like you’d pull a silk handkerchief out of a pocket by one corner.”