Ioviani Seniores


Elite units

A New Horizon: The Reforms of Diocletian

In the later part of the third century AD, the Roman empire was in the midst of civil wars and a severe economic crisis. Generals were being declared as emperors by their troops, dangerously destabilizing the established system of centralized power. During this period of upheaval, Diocles, later Diocletian, was born in the province of Dalmatia, in modern day Croatia. Born of simple stock, Diolcles distinguished himself in the ranks of the roman army, even becoming a cavalry commander under emperor Carus. This was not an uncommon path for an emperor at the time, with many previous emperors using the army to rise socially, with high amounts of social mobility a defining characteristic of this era. His rise culminated in 284 AD, when he became princeps (emperor), inheriting an empire in chaos. He immediately set about to solve these problems through a series of political, military, social and economic reforms.

Head of a togate statue of Diocletian. His gaze toward the sky indicates a link with the gods. His short hair and beard is common among military emperors of the time.
Photo credit: R.V. Huggins

For the army, he changed the traditional structure of 5000 men legions into more fluid and efficient units of 1000 men. Also, legions became more specialized and their equipment was to be provided by the state through the fabricae, which were groups of state-owned warehouses and workshops. The equipment of the soldiers morphed as they started adopting more oval shields and spears with longer spathas as secondary weapons. These changes may have been caused by many of Rome’s enemies being cavalry soldiers such as the Sassanids, the Sarmatians and the Scythians. The organization of the army into Comitatenses and Limitanei may have also began with the reign of Diocletian. The Cohortes Praetoriae, were relegated by the emperor to a secondary role, forming the garrison for the city of Rome, as they were considered too corrupt and ambitious to be trusted in the field. The new imperial guard was formed by the Ioviani and Herculiani regiments, chosen from the legio Iovia and legio Herculiana, famous for their loyalty to emperor Diocletian.

Diocletian, being a man of simple origins, born outside the confines of old aristocracy, disliked the senate and the old oligarchy it represented. He deprived the Senate of most of its powers, relegating it to the role of governing the capital. Power became increasingly centralized in the hands of the new military elites, which were forming the empire. This began the transition towards the separation of the military and civilian roles within the Roman world, which will happen during the reign of Valentianian I. The court system around the emperor became intricate and extremely bureaucratic, as nets of administrators and officials effectively shielded the emperor from the outside world, eventually making it difficult for him to connect to his empire.

Head of Maximian, Musée Saint-Raymond, Toulouse. Born in Sirmium, Maximian was the military arm of Diocletian, leaving politics and reforms to the emperor.

The emperor, considered the first of the roman citizens, was now to be considered a dominus, an authoritarian father figure with links to the gods. Diocletian noticed that the empire was too large to be controlled by a single emperor. It simply was not possible due to its vastness. As a result, in 286 AD Diocletian elevated his old war companion Maximian to a Caesar in the West, based in Mediolanum. Maximian was a perfect candidate for the job as he was a loyal man as well as an able commander. Maximian was later promoted to the rank of Augustus, a full-fledged colleague of Diocletian. The Roman empire thereafter turned into a diarchy, with Maximian ruling the West and Diocletian ruling the East from Nicomedia. Diocletian quickly realized that two emperors alone were not able to maintain stability in the empire. Because of this, he formed the famous tetrarchy, rule of four, an effective division of the empire into four spheres of influence. Maximian had Constantius Chlorus as his Caesar (junior colleague) in the West, based in Trier, modern day Germany, while Diocletian chose Galerius, a peasant who had risen from the ranks of the army as his Caesar, based in Thessalonika.

Emperor Galerius’ portrait head in porphyry, from his palace in Romuliana (Gamzigrad). Emperor Galerius was a rigid military commander and an advocate for the persecution of Christians during the tetrarchy.

Diocletian wanted to stabilize the economy but did not have competent experts at his disposal, so he only managed to debase the Roman coinage by creating a new series of imperial mints. Diocletian later died in 313 AD at his fortified palace at Split, Dalmatia, knowing that his tetrarchic project was doomed to fail. The rise of Diocletian and the tetrarchic period marks a new point in Roman history and it brings the crises of the third century to an end by projecting the empire into an era of political and military stability. The tetrarchic model revealed itself to be a political failure in that it did not account for the ambitions of men, and the impeccable order installed by Diocletian could not be maintained. Diocletian can be considered a pillar of the Roman state as he was an excellent legislator and reformer. The period from the rise of Diocletian onwards would be called the Dominate instead of the Principate as the authoritarian emperor created by Diocletian would become the norm.




Introduction to the Late Roman Army

After the military reforms of Emperor Costantine the Great (306-337 AD), the traditional Roman army as we know it morphed into a more mobile and specialized force, able to deal quickly with foreign and domestic threats that arose throughout the empire. The new army of Costantine was composed of three main groups: the Comitatenses, the Limitanei or Riparienses and the Palatina legions.

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Constantine the Great, Capitoline Museums, Rome. Copyright © 2016 Adriano Zampolini. All rights reserved.

The Comitatenses, heirs of the classical roman legionnaire, were the professional heavy soldiers armed with the long spatha and an oval shield. Their commanders were the Comes, a military figure who later gave birth to the medieval Count.


The Limitanei or Riparienses were paid less, had lower physical requirements but were still full-time professional soldiers who guarded the precarious roman borders, operating as an initial defensive line and an efficient scouting force. They only dealt with small-scale attacks and were usually withdrawn if the situation got extremely dangerous. Their commanders were the Duces, a word later used to indicate all kind of commands.

Limitanei or Riparienses

The Palatina legions, which included the Ioviani, were elite regiments of soldiers and guards associated with the emperor’s presence. Contrary to popular belief, these legions were extremely successful against enemy incursions because of their structure but were considerably drained by civil conflicts.

Herculiani seniores, Palatini

This new defensive model provided by the army of Costantine was called “in depth”, as it guaranteed different levels of protection.


As can be seen in the Battle of Strasbourg (357 AD), the late Romans, guided by Caesar Julian, were more than capable of forming disciplined and effective armies. Therefore, we cannot solely blame the army for the Fall of the Western Empire. In fact, the army remained a capable and efficient force almost until the last breath of the Roman West.

To further prove this, we can look at the Battle of Adrianople (378 AD), during which there were no morale or disciplinary failures by the army, with troops retreating only when the situation became hopeless. The late Roman army was not weaker than its predecessor, instead it had to face extremely precarious situations, often prevailing over insurmountable odds. Despite common belief, the considerable “barbarization” of the army did not cause it to decline in efficiency. According to Ammianus Marcellinus, the soldiers whose origins were outside the Roman Empire were extremely competent and reliable. 


A Knife in the Dark: the Arcani

Missorium of Emperor Valentinian I, surrounded by his bodyguards. From left to right, the second and fifth guard appear to be from the Lanciarii division. The Arcani were disbanded during the reign of Valentinian. Photo credit to MAH, photo J.- M. Yersin, inv. C1241.

The Arcani or Areani were a Roman paramilitary group which acted as a secret police force for the state. Their name means “the hidden ones” or “the secret ones” in Latin, which in and of itself, suggest a role of secrecy. The lack of information about the Arcani is another confirmation of their secretive role. The Arcani were mostly tasked with reconnaissance duties and intelligence missions around the frontiers, giving detailed reports about enemy forces and leaders. The majority of them most likely had military experience, especially “field agents”, whose mission it was to infiltrate enemy territory. We don’t know much about their techniques of subterfuge, but most of their covert operations probably took place during diplomatic gatherings, military expeditions or hostage exchanges. During the late Roman period, they were probably responsible for multiple assassinations of foreign chieftains and kings. They may have worked alongside the Exploratores and Praeventores in supervising the frontier. According to late Roman author and military officer, Ammianus Marcellinus, by the second half of the 4th century AD, the Arcani had become an old and corrupt institution. After being accused of collaborating with the enemy, particularly in regards to the Great Conspiracy, a joint invasion of Britain which included the Attacotti, the Franks, the Saxons and the Picts, the Arcani were disbanded by Count Theodosius the elder, father of future emperor Theodosius I. The Arcani were, and continue to be, often subject of romanticized depictions and wild speculation, especially because very little is known about them. Perhaps the mystery surrounding the Arcani was meant from the beginning?


The Persian Sassanid Army

Mail armoured cataphract.

The Persian army under the Sassanid dynasty of Late antiquity was an extremely efficient force, more loyal and reliable than its Parthian predecessor. The heavy cavalry or cataphracts, taken from the Azadan or minor Persian nobility (feudal nobles) were its core divisions. The 10.000 knights guarding the King of Kings, the Zhayedan or Immortals, were cataphracts as well.

Persian mounted Zhayedan or Immortal.

The 1.000 elite Pushtigban were the same type of heavy cavalry and were based at the capital Ctesiphon. The charge of a shock unit like the cataphracts in battle produced massive damage to enemy divisions and also had great psychological impact on the enemy. In fact, these knights were completely encased in armor, including their faces. According to roman officer and author Amianus Marcellinus, cataphracts looked like “moving iron statues”. The military officers of the Sassanid army were drawn from the Wuzurgan nobility. Light cavalry such as skirmishers and horse archers was mostly supplied by the bellicose tribes of Central Asia like the Hepthalites and the Massagetae. Regiments of light Arab cavalry, mostly provided by the Lakhmids, were always present in Persian armies. The Sassanids also had infantry, though most of their footmen were not trained or professional soldiers but levied and seasonal troops, mostly being armed with spears and large wicker shields. However, an elite body of infantry troops also existed: the Daylamite warriors, Daylamig in Middle Persian.

Daylamites and Sogdian were elite soldiers of the Sassanid army.


These warriors were drawn from the mountainous regions of Northern Iran, the Southern shores of the Caspian Sea. They reached such a high status that 4.000 of them were chosen as private bodyguards by Shah Khosrow II, thereby forming the Gond-i Shahanshah or Army of the King of Kings. The Sassanid army was a very efficient sieging force, using mining techniques, siege towers, catapults and battering rams to siege walled and well fortified cities like the roman fortress of Dura Europos. War elephants from India carried little fortified towers with archer support on top. The elephant corps was under a special chief, known as the Zend-hapet, or “Commander of the Indians”.


High Ranking Officers:

  • Erahn Spahbed – Commander in chief of the army, the equivalent of a Roman Magister Militum.
  • Spahbed – Army commander and field general, Middle Persian Spahpat.
  • Pushtigban Salar – Commander of the Pushtigban bodyguards based in Ctesiphon, Mesopotamia.
  • Eran Anbaraghdad – Officer responsible for the army supplies, of crucial importance while campaigning.
  • Stor-Bizeshk – Senior officer responsible for the health of the steeds, essential for the cataphracts and very knoledgiable about herbs.
  • Arghbed – Commander of a fort or castle.
  • Payghan Salar – Chief of an infantry division, guarded by elite Daylamites, Northern Iranian warriors.
  • Savaran Sardar – Head of a cavalry division.
  • Varhranighan Khvadhay – Commander of the 10.000 Zhayedan bodyguards (the Immortals).


Intelligence Activities in Ancient Rome

Mounted Praetorian wearing a masked helmet usually used in the hippica gymnasia.

In Roman times, intelligence activities were performed by various units whose functions often overlapped. Originally, the Frumentarii, Beneficiarii,  Speculatores and Exploratores were specialized body of troops who provided supplies to the Roman legions and gave them detailed reports about enemy forces. In Imperial times, particularly during the reign of emperor Hadrian, these units gradually became part of a secret service body who loyally served the Princeps. These elite troops were headquartered in the Castra Peregrina on the Mons Caelius in Rome and operated under the command of the Princeps Peregrinorum, a powerful officer responsible for the security of the roman State who answered directly to the emperor.

As displayed on the low reliefs of the Trajan’s Column in Rome, the Frumentarii were, in origin, concerned with the supply of frumentum or corn to the Roman legions. They acted as internal secret police, couriers and security enforcers, carrying out undercover activities both in Rome and in the provinces. We have evidence of collaboration between the Frumentarii and the Cohors Praetoriae or Praetorians in police and security operations in Rome. Most probably, during the 3rd century AD crisis, the Frumentarii played a crucial role in breaching the personal security of emperors, as they had a privileged connection to the Praetorian Guard.

The Speculatores gathered information on Rome’s external enemies and functioned as elite reconnaissance units, messengers and collectors of intellingence. At times, they also acted as assassins and torturers on behalf of the emperor. However, the use of Speculatores was not limited to the Princeps. Provincial guards also employed them for similar purposes. Evidence shows that Speculatores often operated alone, in pairs or small groups and were executed if captured. The Speculatores operated alongside of the Cohors Praetoriae in Rome, in particular of the Equites  Singulares Augusti, the cavalry arm of the Praetorian Guard, and were led by a Centurio Speculatorum Augustorum, a powerful Praetorian officer. The Praetorian Guard or Cohors Praetoriae, were used by emperors as means of terror tactics, assassination and gathering of intelligence, similarly to the Frumentarii. The Speculatores continued to be employed throughout the empire.

The Exploratores were a trained scouting unit to be found in every roman legio. They were sent forward in screening operations and reconnaissance missions, providing excellent situational awareness to roman legions. As evidence from the panels of the Trajan’s Column in Rome shows, they were given first-class horses and equipment in order to increase their mobility when carrying out combat intelligence missions behind enemy lines such as raids, attacks on enemy outposts and foraging operations.

To conclude, the Beneficiarii were specialized soldiers who served under military commanders and governors and had administrative and logistical tasks. At times, even diplomats and courtiers were sent off to foreign courts to spy on enemy kings or rival emperors.

The Frumentarii, Beneficiarii, Speculatores and Exploratores were heavily involved in the violent persecutions of Christians and were most probably the ones who carried out assassinations and tortures.


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