Final answer:
The statement is true; the legion was indeed the basic unit of the Roman army consisting of roughly five thousand soldiers and functioning as a self-sufficient military unit.
Step-by-step explanation:
The assertion that the basic unit of the Roman army was the legion is true. A legion was made up of approximately five thousand soldiers and was a fully self-sufficient unit. Commanded by a legate, the legion had subdivisions of cohorts and centuries, with centurions who were experienced soldiers taking on leadership roles within these groups. Legions encompass both combat troops, including infantry and a small complement of cavalry, and non-combat specialists like engineers, smiths, and cooks. During the Augustan reforms, the Roman military was professionalized, and legions became the standing force responsible for the defense of the Roman empire, with many stationed in various provinces and frontiers.