The Roman army has long been heralded as one of the best organised fighting forces of the ancient world, but how exactly was it organised? The organisation changed a significant amount throughout the history of the Roman Empire but the basic system was always similar, especially after the Marian reforms of 107 BC.
There were two main parts to the Roman army: the auxiliaries and the legions.
The auxiliaries were not Roman citizens, they were recruited from across the empire and had to serve twenty five years in the army before they became a Roman citizen. They also only received around a third of the pay that the legionaries did.
The soldiers who formed the legions were professionals called legionaries and were recruited exclusively as Roman citizens. They too had to serve 25 years in the army but were much better equipped and their last five years of service consisted of lighter veteran duties.
There were normally around thirty legions in the Roman army and each one had between four thousand and six thousand soldiers in it. Each legion was split into ten cohorts and each one of those was made up of six troops of eighty legionaries, called centuries.
The officer in charge of the whole legion was called a legate (Legatus legionis). He was usually a senator who had been appointed by the emperor and often acted as provincial governor for the province they were stationed in.
The Broad Band Tribune (Tribunus Laticlavius) was the second in command, although in battle, another officer would usually take control if needed because of the lack of experience these tribunes often had. They were normally young and often used the position to embark on a senatorial career.
The third in command was the Camp Prefect (Praefectus castrorum). They were long serving veterans who were normally of a lower social status than the Tribunes. Due to their experience, they were in charge of training the legion.
Every legion had five narrow band tribunes (Tribuni Angusticlavii), who were presided over by the broad band tribune. Similarly, they were young and of high social status.
Each century was led by a centurion. There were several ranks of centurion but the most senior was the First File (Primus Pilus). They controlled the first century of the first cohort but were also in charge of the whole first cohort. They often became Camp Prefects.