IN the summer of 1916, a young Oxford academic embarked for France as a second lieutenant in the British Expeditionary Force. The Great War, as World War I was known, was only half-done, but already its industrial carnage had no parallel in European history. “Junior officers were being killed off, a dozen a minute,” recalled J. R. R. Tolkien. “Parting from my wife,” he wrote, doubting that he would survive the trenches, “was like a death.”