Final answer:
In the first century AD, the Roman Army had a total strength of approximately 300,000 soldiers, consisting of roughly 28 legions and an equal number of auxiliary forces. Each legion was made up of 5,400 soldiers and included various non-combat specialists to ensure self-sufficiency.
Step-by-step explanation:
In the first century AD, the Roman Army was a professional standing force that underwent substantial organizational changes from its early days as a volunteer militia. The pivotal unit of the Roman military, the legion, consisted of approximately 5,400 infantry and specialists and 120 cavalry, making it a self-sufficient fighting force. During the Augustan period, there were about 28 legions, each with a number and typically a nickname, many named after the regions where they were originally recruited or had served. Together with the auxiliaries, which were similar in number to the legions at approximately 150,000 men, the total size of the Roman military was around 300,000 soldiers.
The Augustan reforms standardized the internal organization of the legion, with each being divided into 10 cohorts, consisting of 480 men each further subdivided into six centuries led by centurions. Cohorts were made up of centuries, with each century divided into smaller units of 10 men, called tentmates. In addition to the soldiers, the legions included a significant number of non-combat specialists, such as engineers, smiths, and cooks, reflecting the self-sustaining nature of Roman military operations.
Service in the Roman Army was demanding and could last from 16 to 20 years, with rigorous training and harsh discipline. After their term of service, soldiers were rewarded with a form of pension and, sometimes, land. Auxiliary forces, upon completing their service, were granted Roman citizenship, a practice that became universal in the early second century.