A legion is a large military unit historically associated with the ancient Roman army. Typically, a Roman legion consisted of about 4,000 to 6,000 soldiers, organized into smaller groups called cohorts. Each legion was commanded by a legate and played a crucial role in the expansion and defense of the Roman Empire. In modern contexts, the term "legion" can refer to any large group of people united for a common purpose. For example, the American Legion is a veterans' organization that supports former military personnel and their families. The concept of legions has also been used in literature and popular culture to describe vast numbers of followers or supporters.