Later Roman Army

Military Organization

By PR Gray

Military Organisation

The organisation of the army can be split into two broad types. The first is similar to that of the earlier empire with some modifications. The second becomes apparent during the reigns of Gallienus, Diocletian and Constantine the Great. A number of new units and troop types were introduced, although the troops may be similar to earlier soldiers in terms of employment and equipment.

Most historians support theories that the Roman military began to change radically in the second half of the 3rd Century AD. While there is plenty of conjecture, there is a paucity of archaeological evidence to substantiate the various theories. Much of the military organisation seems to have been similar to that of the early Imperial periods. The bulk of the military comprised of legions and auxiliary units with augmentation by allies, mercenaries and prisoners of war.

Throughout Roman history, it is possible to see that both complete units and detachments from units fought in campaigns. Major operations such as invasions, particularly those of the emperors or their designated commanders, would have a core of full strength units supported by detachments. The need to garrison forts, create campaign armies and protect lines of communication meant that the detachment of sub-units (called vexillatio, vexillationes (plural)) was a common occurrence.

The armies of Gallienus and his successors cover the period of 260s-280s. Gallienus developed a single heavily centralised field army of infantry vexillationes detached from border troops and cavalry, including many new units of Moors, Dalmatians and Illyrians. Mobility was important to this army and infantry were possibly mounted to keep pace with the cavalry. The army was based in Milan, from where it could strike at the Rhine and Danube frontiers and protect Italy from invasions from these frontiers and the breakaway Gallic "empire". Border troops remained basically unchanged in organisation.

The establishment of long term and permanent detachments is noticeable during the 4th Century, although this practice may have been ongoing for many years. It is obvious amongst the legions particularly because of their size (up to 6000 men). Detachments of auxiliaries may also have been established, although it is less apparent because of their smaller numbers (500-1000). Legionary detachments are recorded in the Notitia Dignitatum with the names, numbers and references to garrisons of the parent formation. The use of junior and senior in unit titles has also been postulated as indication of the splitting of parent units into detachments. What is less obvious is whether or not units were recruited back to their full or paper strength.

A significant increase in the military is attributed to Diocletian (284-305) to about 400-500,000. (In the 6th Century, John the Lydian gives the figure 435,266 and Agathias suggested a total force of 645,000 men.) To raise the additional troops, Diocletian made military service hereditary and instituted a new system of conscription based on land tax (protostasia): a burden that fell primarily on agricultural population, as landowners were responsible to provide specified quotas of conscripts. Not all parts of the empire were subject to conscription. In the provinces where population was deemed to lack the required mettle, the recruiting tax was converted into cash payments known as recruit gold (aurum tironicum). This money was used to provide bounties to attract desirable and willing recruits.

Theories based on the multiplication of the military have been partially attributed to Diocletian's creation of the dual Augustus and Caesar system (tetrarchy) with each having command of a part of the military. The Christian author Lactantius, who despised Diocletian (who was a pagan), stated that the creation of the tetrarchy meant that army and Imperial civil service were quadrupled, although it was more likely that they were divided into four uneven parts.

During these reforms, it is difficult to determine to what extent Diocletian and his colleagues expanded the military. The deployment of the army was regularised in an attempt to restore the frontier system in a modified form. The provinces were restructured and many were allotted two legions plus auxiliaries. This required an increase in the number of units to give a total of more than 50 legions compared to the 2nd Century total of about 34 legions. Depending on your source, the total of legions added by the mid-4th Century was up to 35. Even ad hoc groups, often called numerus (numeri-plural), had become part of the established military prior to Diocletian's reforms.

Although the structure and establishment strength of these new legions were similar to that of earlier units, some of the tetrarchic legions were formed by combining existing units of the auxilia. Many auxiliaries would have been Roman citizens following the granting of citizenship to all inhabitants of the empire in 212 AD. This had been one of the distinctions between the two types of units with some auxiliary cohorts receiving citizenship as a reward (and included there after in the unit's title - Civium Romanorum) and the majority receiving it upon retirement. Historians have debated the specific differences between the legions and the auxiliaries apart from status. Some historians argue that there was little difference in arms, armour and tactics. One possible distinction may have been the positioning of the auxiliaries in the front line with the legions acting as reserves (as was the case in the Battles of Mons Graupius and Strasbourg). This would usually result in a higher casualty toll amongst the auxiliaries (a complaint of the Goths following the Battle of the Frigidius River with the Goths accusing the Emperor, Theodosius the Great, of deliberately sacrificing them).

Constantine and his successors are considered the developers of regional field armies, which were fashioned from detachments of the frontier units and the creation of new units. Each emperor or caesar had a field army from which regional field armies could be developed during the era of the tetrarchy and before the solo reign of Constantine. The military was divided amongst Constantine's three sons in 337 AD and probably remained divided, either as permanent field armies or as temporary forces. In the 5th Century, there were five eastern field armies (Thrace, Illyria, Orient and two praesentales), and at least four in the west (Britain, Africa, Gaul and Italy) according to the Notitia Dignitatum.

The army was divided into two major categories by the reign of Constantine the Great: the border or frontier troops (limitanei, castellani, burgarii and riparienses/ripenses/ riparii (troops of water frontiers)), and field troops (comitatenses). Historians tend to suggest that the former degenerated to second class troops or militia because of lower pay and status. While there is evidence of such a trend, the field armies were also subject to deterioration in quality. Comitatenses became static garrisons for major urban centres and may have consequently lost some of their ardour. Limitanei were absorbed into the field armies and became known as psuedocomitatenses, although ranking below the original field units, but above their former peers in the limitanei. Comitatenses may have been demoted or transferred to the limitanei.

The limitanei consisted of infantry legiones, cohortes and numeri, and cavalry vexillationes, alae and cunei (wedges). The numeri and cunei may have been smaller units than the corresponding cohortes and alae, possibly only 50% as strong (or the names were just used to identify units other than those of the older established military). All of these units garrisoned the traditional military posts that had been in existence for centuries and represented the majority of the military's manpower (about 2/3). By the end of the 4th Century, there are indications that the limitanei received the less desirable manpower (married, sick, lame, etc.). This probably contributed to the decline in unit quality. One must remember that the limitanei were still expected to provide the first line of defence and conduct cross-border operations, so their quality may have been more dependent on leadership than the quality of the troops. In the 6th Century, limitanei were still present throughout the empire and the Emperor Justinian raised units in reconquered provinces (Africa and Italy).

The comitatenses or field armies were derived from the Sacer Comitatus (sacred following), which was the imperial court/bureaucracy. These were the original companions (comites) or retinue of the emperors. One of the earliest examples of a comitatenses was the infantry and cavalry force organised by the Emperor Gallienus and stationed at Milan. This was more than just units of the existing bodyguard (Equites Singulares Augusti) and Praetorian Guard as troops were drawn from units throughout the empire. Its main function was to accompany the emperor on campaign. Its secondary function was possibly to serve as a central reserve.

Armies accompanying the emperors were termed praesentales ("in praesenti" meaning in the presence of the emperor). The formation of independent regional field armies (Gaul, Illyricum and Orient) under magistri militum (masters of the military) supplemented praesentales armies of the emperors and ceasars. Within field armies, there was a distinction between units as some were simply comitatenses and others given the higher status of palatina. Both types were probably of varying quality depending on experience and leadership, although the Notitia Dignitatum ranks the palatina units before those designated comitatenses. Initially, there were only a few palatina units. These may have been part of the original comitatenses of Gallienus, although Constantine the Great is commonly credited with their formation into a field army. (Possibly these were the units that he used during his first campaigns in the west and participated in the Battle of Milvian Bridge in 312 AD.

Many of their names suggest ties to Gallic and Germanic groups of the region initially controlled by Constantine.) Transfers between regional and praesentales armies blurred the distinction between palatini and comitatenses. Many comitatenses units had periods of inactivity, which may have contributed to a laxity in training and readiness. By the 6th Century, many units were permanently garrisoned in urban centres. This tended to make them less mobile.

Guards

In addition to the field units, there were the Praetorian Guard and other units raised to guard the emperor, senior officials and their capitals. The Praetorians are normally associated with the garrison of Rome, although they did provide contingents for operations along the frontiers and in the many civil wars. Another long-term guard unit was the Equites Singulares Augusti, later known as the equites dominorum nostrorum or comites dominorum nostrorum (companions of our lord). In addition, there was a body of men called "protectores et domestici".

There were two units; one of infantry under the comes domesticourm pedites and one of cavalry under the comes domesticorum equites (according to the Notitia Dignitatum). Their origin is not entirely clear, but in any case they served as the emperor's bodyguard. In the 4th Century, this was an honoured position and personnel were detached from the protectores for important jobs and were later promoted to serve as senior officers. In effect, it served as a sort of officers' training corps. In the 5th Century, the troops served permanently as the emperor's bodyguard (possibly ornamental) and were not detached for service elsewhere. There was also a smaller unit of bodyguards, the candidati (Barker and Elton say there were 40, and Jones (pg 613) states the 40 candidati were provided from the scholae).

There were also the scholae (taken from hall of the palace (schola), in which they attended the emperor), who replaced the Praetorian Guards after 312 AD (Speigel prefers the argument that they only replaced the Equites dominorum nostrorum and the Praetorians were just disbanded not replaced). There were initially five units, and later five in the west and seven in the east. Each may have numbered 500 and were all cavalry. Their quality was probably as variable as that of the comitatenses. In the 5th Century, a new guard unit, the Excubitori, was raised to provide the emperor in Constaninople with a competent guard unit. By then, positions in the scholae were being sold to the highest bidders as the pay and benefits were attractive to many aspiring members.

Finally, senior officials were permitted bodyguards. These were usually drawn from units and personal troops (see below). Such contingents could provide the nucleus for rebellious forces in the civil conflicts, and expeditionary forces. In the early empire, imperial governors and senior generals were permitted guards drawn from legionary and auxiliary units, called singulares. For example, the Singulares Legati Legionis was the bodyguard of a legate or military governor drawn from legionary troops.

Foreigners

Roman armies made much use of foreign soldiers, as specialists (slingers, archers, cavalry, scouts, etc.) and to augment the Roman units. Their presence in the army was continual from the early Roman armies to the late imperial ones. There is no conclusive evidence suggesting that the enrolment of foreigners affected the battlefield effectiveness of the army. Initially, the imperial auxiliaries were primarily non-citizens, although the granting of Roman citizenship in 212 AD removed one of the main distinctions between the legions and the auxiliaries. Roman forces adopted foreign concepts and foreign militaries adopted Roman ones, a trend that tended to blur the origin of some of them.

Basically no source of manpower was exempt from recruitment. Regular units received recruits from foreign communities settled within the empire (sometimes known as laeti and gentiles), and neighbouring foreign groups. The Roman emperors often permitted barbarians to settle on uninhabited lands of the empire to supplement the supply of soldiers and taxable wealth. Burns says this was consistent with the Roman practice of "receptio," roughly translated as surrender or submission. Prisoners of war and contingents from defeated forces were accepted (dediticii, tributarii). The provision of recruits (foederati) was a common part of a treaty (foedus) with foreign groups.

In addition, allies provided contingents for a specific period of service or a campaign (sometimes referred to as symmachoi, which is a Greek word, rather than the Latin socii—note again the mixing of the languages). The distinction between these various terms is unclear, despite efforts by historians to associate them with specific groups from which recruits were acquired. Foederati became regular units equipped by the state and added to the military organisation, and later composed of Roman and foreign soldiers.

The sons of foreigners were expected to serve in the military (probably based on the granting of citizenship to their fathers and thus making them subject to the law instituted by Diocletian). While historians tend to focus on the German elements in the army, the Romans recruited from many foreign and domestic groups. Moors, Sarmatians, Alans, Illyrians, Arabs, Isaurians, Armenians, Huns, Celts and Germans tend to be among the better known ethnic groups because of the use of their names in unit titles.

In the 5th Century, the eastern army included a comes foederatorum (count of the federates). His duties may have included overseeing the enrolment of foederati (including the Goths settled in Thrace following the Battle of Adrianople) and/or commanding foederati on campaign. The Emperor Maurikius (Maurice) held this position before becoming emperor in the late 6th Century.

Using the French army of the mid-17th Century as an example, Cardinal Richelieu believed that a foreign soldier or mercenary equalled three men because it meant one more civilian working and paying taxes, one willing soldier and one less soldier for any potential enemy. It was probably also true in the Roman army as recruiting was predominantly done in the regions closest to combat operations and in the outer provinces (which Elton argues were heavily militarised zones).

One characteristic of Germanic and other ethnic warriors was a bond of loyalty to a charismatic leader. They served faithfully in the forces of the emperors, usurpers and "warlords", who seemed to have been able to establish their sway over these troops. The personal loyalty was probably important given the frequency of civil strife during which leaders endeavoured to bribe and coerce troops to switch their allegiance.

One parallel between the Roman and German forces was the development of the companions, also known as comitatus and antrustiones. They were the personal following of a leader such as the Gothic guards of Gallia Placidia, "queen of the Visigoths" and sister of the western emperor, Honorius. Julius Caesar and Augustus established predecessors of the Equites Singulares Augusti with the formation of the Germanic bodyguards of the Germani Corporis Custodes.

Personal Contingents

The emperors and their appointees were not the only leaders to have bodyguards. Senior officials and landowners raised unauthorised contingents of bodyguards. The most common name for them was bucellarii (derived from bucellam, bread or "hard tack" biscuits) in the 5th Century (the name is not recorded in earlier times, although private retinues probably existed then). The official bucellarii swore oaths of allegiance to both their employer and the emperor. Other bodyguards were probably only loyal to their employers. Bodyguards were both Roman and foreign soldiers.

Patronage was important to both the regular and private military forces. The rise and fall of groups can be linked to the leaders. Emperors and generals favoured specific groups for their guards. Such forces might be disbanded (or killed) on the death or demise of their patron. This seems to be particularly true of forces raised by usurpers, who were defeated. Their forces would be amalgamated into the winner's army, although some units may have been retained (and possibly renamed).

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© Copyright 2000 by Terry Gore
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