A legion was commanded by a legate appointed by the emperor. The legate was often a senator, too. Other senior officers included 6 tribunes, of whom one was the commander (tribunus lacticlavius) and five tribunes were from the equestrian (tribuni angusticlavi). The camp prefect (administrator - praefectus castrorum) was originally the highest rank centurion (primus pilus) promoted to equestrian and was also in charge of the legion in the absence of the legate and the first tribune.
Centurions were professional legionary officers in charge of individual centurions. Based on their position in the 2nd – 10th cohort, they were called pilus prior, pilus posteriori, princeps prior, princeps posteriori, hastatus prior and hastatus posterior. Centurions in the first cohort of five centurions were named primi ordines and they had a superior position in the legion. The senior and chief centurion of the 1st cohort was primus pilus, followed by princeps, hastatus, princeps posterior and hastatus posterior. Other junior officers and non-commissioned officers, e.g. eagle carrier (aquilifer), doctors and attendants, veterinarians, administrative officials but also executioners, etc. were also part of the legion. A colour-bearer (signifer), trumpeter (cornicen), guard officer (tesserarius), deputy commander (optius), etc. were present in every century.