World War I, which began a century ago this summer, has been a hot topic among authors and documentary filmmakers. For her contribution, Cornell University history professor Isabel V. Hull gives a thorough and thoughtful investigation into one of the war’s trigger points, the legal issues surrounding Germany’s invasion of Belgium. The assault widened the war by drawing in Britain, committed by treaty to protecting Belgian neutrality. Germany was a signatory to that same treaty, but its army command believed that “military necessity” trumped international agreements and, as Hull finds, Germany’s military seldom coordinated its planning with the country’s civilian leaders. A Scrap of Paper is a luminous account of war and international law with implications for recent and ongoing world conflicts.