Final answer:
During World War I, First Sergeants carried a book containing the professional histories of their company members, maintaining the unit's historical record and aiding new First Sergeants in familiarizing themselves with their company's lineage.
Step-by-step explanation:
The book that First Sergeants often carried during World War I, which contained the names and professional history of everyone in their company, provided a continuous record of unit history and was crucial for maintaining the group's historical lineage. This record-keeping helped to ensure that, despite the chaos and destruction of war, the contributions and sacrifices of individual soldiers would not be forgotten. It was also a tool for incoming First Sergeants to quickly gain an understanding of the company they were taking over.
Similar to the way the American soldiers carried personal items and memorabilia, which are recounted in stories like Tim O'Brien's The Things They Carried, this book served as a testament to the experiences and identities of the soldiers. Understanding what soldiers carried, both physically and mentally, provides insights into their lives during the conflict, their personal stories, and the shared history that shaped the American Army during World War I and influenced the United States long afterward.