At the outbreak of the First World War, an entire generation of young men charged into battle for what they believed was a glorious cause. Over the next four years, that cause claimed the lives of some 13 million soldiers--more than twice the number killed in all the major wars from 1790 to 1914. But despite this devastating toll, the memory of the war was not, predominantly, of the grim reality of its trench warfare and battlefield carnage. What...