Republic
After the Marian reform, the ranks in the Roman army are as follows
General officers
* Imperator:victorious general. Title granted by acclamations by the army to its leader.
The command of the Roman army is generally entrusted to a consul, the highest magistrate of the city of Rome.
* Legatus (legalization) deputy of the commander of the army, he can be delegated to command cavalry, reserves or even a legion.
Legions
* Tribuni militum (military tribunes) senior officers who command a legion on a rotating basis. There are several types of tribunes:
o Tribuni militum rufuli tribunes appointed by the general and not elected by the comitia.
o Tribuni militum a populo tribunes elected by the comitia among the young people of the equestrian order.
* Centuriones (centurions) sulbaltern officers commanding a centuria. They are ranked by their place in each cohort:
o Primus pilus (primipile), first centurion of the first cohort
In each cohort the centurions are subordinate:
*
o Pilu prior commanding the 1st century
o Princep prior commanding the 2nd century
o Hastatu prior commanding the 3rd century
o Pilu posterior commanding the 4th century
o Princep posterior commanding the 5th century
o Hastatu posterior commanding the 6th century
* Main equivalents of non-commissioned officers:
o Optione equivalents of warrant officers
o Signiferi standard-bearers
o Tesserarius sergeant-major
o Campidoctores instructors
o Pecuarii subsistence worker
o Architects
o Military doctors
o Conductor
o Musicians
* Militia caligata enlisted men, individually called miles.
o Immune soldiers exempt from all corvée
o Munifice soldiers subject to corvée
Cavalry wings
* Præfecti (prefects) commanding a cavalry tower.
* Decuriones (decurions) commanding a decurie group of ten horsemen.
* Equites riders.
Navy
* Navarque commanding several ships
The trierarch with a rank probably lower than that of the centurion of legion
Artillery
The praefectus fabrum directed the artillery and the military engineers.
Honorary rank
* Evocati
Empire
Late Empire:The army was divided by Constantine (306-337) into two main groups:the Limitanei (border guards) and the Comitatenses (mobile elite troops in charge of military campaigns.) The ranks of late Roman leaders are:the Dux, the Comes (Count), the Magister Peditum (who commands the infantry), the Magister Equitum (in charge of directing the cavalry), the Magister Militum (Master of the soldiers) who is in fact the generalissimo. During the decay of the Western Empire, the Magister Militum is in fact the strongman of the empire, the true leader of all Roman forces. The most famous of them is Flavius Aetius, unsung hero of French history, to whom we owe the victory over the Huns of Attila at the Catalaunian Fields (June 451). The privates of rank are graded according to their seniority, the most favored being exempted from corvées and other heavy work. Depending on their rank, they receive larger rations. Alongside this, it is essential to speak of the Foederati, Romanized barbarian conquerors who, in exchange for land and money, settled in the empire by entire peoples. They keep their weapons and their original military apparatus and are not always very reliable. Many wars oppose the last "true Romans" to these auxiliaries often eager for new territories and very inclined to violate treaties that the central Roman power n can't get more respect.