In 1940 Ernest Hemingway published For Whom the Bell Tolls, his most ambitious novel, when he was forty-one years old and at the peak of his powers. He was the best known writer in the world, and in 1945 readers awaited his fictional treatment of World War II, which he had covered as a reporter. He had written novels set during World War I and the Spanish Civil War in the 1930s. But Hemingway had sustained two major concussions during World War II. As a result, he suffered from headaches and had trouble concentrating. Worst of all, his memory became impaired, and he had difficulty writing words. He had always been a disciplined writer and he began a strict program to resume his work. It was first necessary for him to limit his alcohol consumption. According to Hemingway's biographer Carlos Baker, he began...