Centurion of Legio III Gallica

The first unit mentioned on Castus's inscription is the legio III Gallica – for most of the 2nd and 3rd centuries the unit was stationed in Syria. He held the rank of centurion in this legion – most Roman soldiers only achieved the rank of centurion after about 15–20 years of service, but it was not unknown for some politically connected civilians of the equestrian class to be directly commissioned as centurions upon entering the Army, though these equestrian centurions (known as "ex equite Romano") were in the minority.^[16] We cannot tell whether or not Castus had a lengthy career as a legionary soldier before attaining the centurionate, or whether he was directly commissioned at this rank, as the vast majority of career centurions' inscriptions do not mention any ranks that they might have held below the centurionate.^[17] Successful officers often omitted the record of any ranks lower than primus pilus,^[17][18] as Castus did on his memorial plaque.

Centurion of Legio VI Ferrata

From the middle of the 2nd century until at least the early 3rd century the legio VI Ferrata was stationed in Judea.

Centurion of Legio II Adiutrix

From the early 2nd century onward the legio II Adiutrix were based at Aquincum (modern Budapest) and took part in several notable campaigns against the Parthians, Marcomanni, Quadi and, in the mid-3rd century, the Sassanid empire.

Centurion and Primus Pilus of Legio V Macedonica

The legio V Macedonica was based in Roman Dacia throughout the 2nd century and through most of the 3rd – the unit took part in battles against the Marcomanni, Sarmatians and Quadi. The legio V Macedonica after 185 CE was called Pia Fidelis or Pia Constans (shortened as P.F. or P.C.), so Castus served in this unit as centurion and primus pilus before 185 CE (in the inscription these nicknames are missing).

Praepositus of the Misenum fleet

Castus next acted as Provost (Praepositus) of the Misenum fleet in Italy. This title (generally given to Equites) indicated a special command over a body of troops, but somewhat limited in action and subject to the Emperor's control.^[19]

Praefectus of Legio VI Victrix

The Legio VI Victrix was based in Britain from c. 122 AD onward, though their history during the 3rd century AD is rather hazy. Throughout the 2nd century AD and into the 3rd, the headquarters of the VI Victrix was at Eboracum (modern York). The unit was removed briefly to Lugdunum (Lyons) in 196 AD by Clodius Albinus, during his doomed revolt against the emperor Severus, but returned to York after the revolt was quelled – and the unit suffered a significant defeat – in 197 AD.

Castus's position in the Legio VI Victrix, Prefect of the Legion (Praefectus Legionis), was equivalent to that of the Praefectus Castrorum.^[20] Men who had achieved this title were normally 50–60 years old and had been in the army most of their lives, working their way up through the lower ranks and the centurionate until they reached Primus Pilus^[21] (the rank seems to have been held exclusively by primipilares^[22] ). They acted as third-in-command to the legionary commander, the legatus legionis, and senior tribune and could assume command in their absence.^[20][21] Their day-to-day duties included maintenance of the fortress and management of the food supplies, sanitation, munitions, equipment, etc.^[21][23] For most who had attained this rank, it would be their last before retirement.^[23] During battles, the Praefectus Castrorum normally remained at the unit's home base with the reserve troops,^[24] so, given his administrative position and (probably) advanced age, it is unlikely that Castus actually fought in any battles while serving in Britain.

Castus could have overseen vexillations of troops guarding Hadrian's Wall, but his inscriptions do not provide us with any precise information on where he might have served while in Britain. Given his duties as Praefectus Legionis, it is reasonable to assume that he spent some – if not all – of his time in Britain at the VI Victrix's headquarters in York.

It is interesting that the title is spelled (P)RAEFF on Castus's sarcophagus – doubled letters at the end of abbreviated words on Latin inscriptions usually indicated the plural (often dual) and some legions are known to have had multiple praefecti castrorum.^[21][23] The title is given in the singular on the memorial plaque, though, so we might have a scribal error on the sarcophagus. If not, then Castus was probably one of two prefects of this legion.

Dux Legionum Trium "Britanicimiarum"

Before finishing his military career, Castus led an expedition of some note as a Dux Legionum, a temporary title accorded to officers who were acting in a capacity above their rank, either in command of a collection of troops (generally combined vexillations drawn from legions^[25]) in transit from one station to another or in command of a complete unit (the former seems to be the case with Castus, since the units are spoken of in the genitive plural).^[26]

Procurator Centenarius of Liburnia

Exceptionally talented, experienced and/or connected Praefects Castrorum/Legionis could sometimes move on to higher civilian positions such as Procurator,^[21] which Castus indeed managed to accomplish after retiring from the army. He became procurator centenarius (governor) of Liburnia, a part of Roman Dalmatia, today's Croatia. (centenarius indicates that he received a salary of 100,000 sesterces per year). Castus was appointed procurator centenarius of the province of Liburnia with ius gladii, the power to put anyone, even Senators, to death. Nothing further is known of him. Other Artorii are attested in the area, but it is unknown if Lucius Artorius Castus started this branch of the family in Dalmatia, or whether the family had already been settled there prior to his birth (if the latter, Castus might have received the Liburnian procuratorship because he was a native of the region).