Not to be confused with Decurion (administrative)

Decurion (administrative)

A decurion was a member of a city senate in the Roman Empire. Decurions were drawn from the curiales class, which was made up of the wealthy middle class citizens of a town society....

A decurion (Latin: decurio, plural decuriones) was a Roman cavalry

Roman cavalry

Roman cavalry refers to the horse mounted forces of the Roman army through the many centuries of its existence.- Early cavalry Roman cavalry (Latin: equites Romani) refers to the horse mounted forces of the Roman army through the many centuries of its existence.- Early cavalry Roman cavalry...

 officer in command of a squadron (turma

Turma

A turma was a cavalry squadron in the Roman army of the Republic and Empire. In the Byzantine Empire, it became applied to the larger, regiment-sized military-cum-administrative divisions of a thema....

) of cavalrymen in the Roman army

Roman army

The Roman army is the generic term for the terrestrial armed forces deployed by the kingdom of Rome , the Roman Republic , the Roman Empire and its successor, the Byzantine empire...

.

Republican army

During the Roman Republic

Roman Republic

The Roman Republic was the period of the ancient Roman civilization where the government operated as a republic. It began with the overthrow of the Roman monarchy, traditionally dated around 508 BC, and its replacement by a government headed by two consuls, elected annually by the citizens and...

 a "Polybian" legion

Roman legion

A Roman legion normally indicates the basic ancient Roman army unit recruited specifically from Roman citizens. The organization of legions varied greatly over time but they were typically composed of perhaps 5,000 soldiers, divided into maniples and later into "cohorts"...

 (ca. 300–88 BC) of citizen-levies had a cavalry complement of 300 horse, divided into 10 turma

Turma

A turma was a cavalry squadron in the Roman army of the Republic and Empire. In the Byzantine Empire, it became applied to the larger, regiment-sized military-cum-administrative divisions of a thema....

e (squadrons) of 30 men each. Each turma was led by 3 decurions, who were elected by the squadron members themselves. Although decurio literally means "leader of 10 men", it does not appear that a turma was sub-divided into 3 troops of 10 men each. Instead, one decurion would act as squadron commander and the other two as his deputies. All decurions were members of the Roman equestrian order, as were many of their subordinates.

Imperial army

In the imperial Roman army

Imperial Roman army

The Imperial Roman army refers to the armed forces deployed by the Roman Empire during the Principate era .Under the founder–emperor Augustus , the legions, which were formations numbering about 5,000 heavy infantry recruited from Roman citizens only, were transformed from a mixed conscript and...

 of the Principate

Principate

The Principate is the first period of the Roman Empire, extending from the beginning of the reign of Caesar Augustus to the Crisis of the Third Century, after which it was replaced with the Dominate. The Principate is characterized by a concerted effort on the part of the Emperors to preserve the...

 (30 BC - AD 284), a decurion also commanded a cavalry turma

Turma

A turma was a cavalry squadron in the Roman army of the Republic and Empire. In the Byzantine Empire, it became applied to the larger, regiment-sized military-cum-administrative divisions of a thema....

of ca. 30 men, but now without colleagues. In common with all soldiers in the imperial army, decurions were long-service professionals, the majority volunteers.

A Roman imperial legion

Roman legion

A Roman legion normally indicates the basic ancient Roman army unit recruited specifically from Roman citizens. The organization of legions varied greatly over time but they were typically composed of perhaps 5,000 soldiers, divided into maniples and later into "cohorts"...

, which contained ca. 5,500 men, contained a small cavalry arm of just 120 men (i.e. 4 turmae). Since the average number of legions deployed was ca. 30, imperial legionary cavalry numbered only ca. 3,600, out of a total of ca. 80,000 cavalrymen deployed by the imperial army. There were thus ca. 120 cavalry decurions in the legions at any given time.

The vast majority of the imperial cavalry was in the regiments of the auxilia, the non-citizen corps of the regular imperial army (whose recruits were mainly imperial subjects who did not hold Roman citizenship (known as peregrini

Peregrinus (Roman)

Peregrinus was the term used during the early Roman empire, from 30 BC to 212 AD, to denote a free provincial subject of the Empire who was not a Roman citizen. Peregrini constituted the vast majority of the Empire's inhabitants in the 1st and 2nd centuries AD...

). An ala (literally "wing"), which was an elite all-cavalry regiment, contained 480 horse (16 turmae, thus 16 decurions). A double-strength ala (ala milliaria) contained 720 horse (24 turmae). Circa 90 alae were deployed in the time of emperor Hadrian

Hadrian

Hadrian , was Roman Emperor from 117 to 138. He is best known for building Hadrian's Wall, which marked the northern limit of Roman Britain. In Rome, he re-built the Pantheon and constructed the Temple of Venus and Roma. In addition to being emperor, Hadrian was a humanist and was philhellene in...

 (ruled 117-38). In addition, the auxiliary corps included a type of regiment known as a cohors equitata, an infantry unit with a cavalry complement of 120 horse (4 turmae; 8 in a double-strength unit). Around 180 such regiments existed under Hadrian. There were thus ca. 2,500 decurions serving in the auxilia at any given time.

In the imperial period, decurions were no longer conscripted Romans, commoners who were often promoted from the ranks, but could also be members of native tribal aristocracies. (Roman knights at this stage only provided the overall commanders (praefecti) of the auxiliary regiments). Thus, decurions in the imperial army were of far lower social status than their predecessors in the Republican cavalry. The latter were not only Roman citizens, but also aristocrats, whereas auxiliary decurions were mostly commoners and non-citizens (until AD 212, when all imperial subjects were granted citizenship). Even if they belonged to a native aristocracy, they ranked lower than a commoner Roman citizen in the status-conscious Roman empire.