Roman Army: Principate

In this blog, we delve into the Roman legionary from the early imperial period. But before we begin, we briefly look back at the origins of the Roman professional army.

In the previous blog, we discussed how the Roman professional army emerged after the significant losses of the 2nd Punic War (218-201 BC) and the subsequent massive territorial expansion of the Roman Republic. Originally, the army consisted of conscripts who had to serve in the military for a limited period. This led to economic and social imbalance. Therefore, more and more volunteers from the poorer classes with citizenship were recruited as professional soldiers. Professional soldiers served in the army for periods of 6 years. After the Social War (91-88 BC), the legions as most people know them came into being.

The legions formed mini-societies. And during the Roman Civil War 49-45 BC, it became clear that the loyalty of the legionary was primarily towards his general, a pattern similar to the Roman client-patron relationship of citizens, but armed. After the assassination of Julius Caesar and the subsequent war of the Second Triumvirate (32-31 BC), Octavian won total power and became Emperor Augustus, the first emperor of the Roman Empire.  

After gaining undisputed power in 27 BC, Augustus faced the challenge of an army that had grown significantly due to recruitments during the Roman civil wars. At the same time, the army lacked proper organization to both defend and expand the empire. Despite disbanding most of the legions of his defeated rival Marcus Antonius after his victory, Augustus had 50 legions under his command. Around this time, the army consisted of legions, auxilia and Foederati (allies). By the end of his reign, the army numbered about 250,000 men, divided into 25 legions and 250 auxilia units.

The first priority was to reduce the number of legions to a sustainable level. Fifty legions meant too high a recruitment pressure for a male citizen population of only about two million. The emperor retained slightly more than half of his legions, disbanded the rest, and settled their veterans in 28 new Roman colonies. The number of legions remained close to that level until the early third century (ranging between 25 and 33).

Augustus extended the period in which a professional soldier could serve. Under the late Republic, a Roman citizen aged 16 to 46 could legally serve a maximum of sixteen years in the legions, of which a maximum of six years consecutively. In 13 BC, Augustus issued the decree that sixteen years was the standard term of service for legion recruits, with four additional years as reservists (evocati). In 5 AD, the standard term was extended to twenty years plus five years as a reservist. Thus, the legionary was assured of an entire career as a soldier.

Augustus changed the command structure of the legions. In the Republic, each legion was under the command of six equestrian tribunes who took turns commanding. In the late Republic, however, these military tribunes were overshadowed by higher-ranking officers of senatorial rank, the legati. Augustus appointed a legatus to permanently command each legion, with a term of office lasting several years.

The ambitious expansion plans of Augustus for the Roman Empire (including extending the border to the Elbe and the Danube) soon demonstrated that 28 legions were not sufficient. From the Cantabrian Wars, which aimed at the annexation of the mineral-rich mountains in the northwest of Spain, his 41-year reign experienced an almost unbroken series of major wars that often demanded the utmost from manpower.

The basic unit of the legion was the centuria, which literally means "one hundred men," but in practice consisted of 80 men during the Principate. The most important tactical subunit of the legion was the cohors, which contained six centuriae, totaling 480 men. Each legion consisted of 10 cohorts, or 4,800 men (approximately 5,000 including the small legionary cavalry of 120 horsemen and officers). Around 100 AD, however, the First Cohort was divided into only five centuriae, but with double strength of 160 men each, resulting in a total of 800 men. From that point, a legion thus counted approximately 5,300 men.

Each legion contained a small cavalry unit of 120 men. They performed tasks such as messengers, scouts, and escorts for senior officers.

The legion consisted of heavy infantry. Although virtually unbeatable on the battlefield by non-Roman infantry, it was a large, inflexible unit. Support from  auxilia troops such as archers and cavalry was indispensable for the proper functioning of a legion.

Augustus retained the services of numerous units of native allies. But there was an urgent need for additional regular troops, organized, if not fully equipped, in the same manner as the legions. These troops could only be recruited from the vast pool of non-citizens of the empire, known as peregrini. In the early 1st century, there were about nine times as many peregrini as Roman citizens. The peregrini were now recruited into regular units of cohorts (about 500 men), forming auxiliary troops without citizenship rights and known as auxiliae. By 23 AD, Tacitus reported that the auxiliae were approximately the same size as the legions (around 175,000 men). The approximately 250 regiments were divided into three types: a fully infantry regiment (about 120 regiments); an infantry unit with a cavalry contingent, the cohors equitata (80 units); and a fully cavalry unit, the ala (plural: alae, literally: "wing"), of which about 50 were originally established.

During the Principate, there is evidence of ethnic units of barbari outside the normal auxilia organization fighting alongside Roman troops. These units were called socii ("allies"), symmachiarii or foederati. An estimate places the number of foederati in the time of Trajan at about 11,000, divided into approximately 40 units of about 300 men each.

The foederati first officially appear on Trajan's Column, where they are depicted as generalized half-naked barbarians. This was likely to distinguish between foederati and the regular auxiliae. 

As military units composed entirely of Roman citizens, the legionaries represented Rome in person. Thus, the lower class of Roman Italy, which did enjoy citizenship, held a privileged position compared to the rest of the population (peregrinus). Their ancestors had paid dearly for this during the Punic Wars. This superiority was reflected in the pay and additional benefits enjoyed by legionaries. Moreover, legionaries had better equipment than auxiliary troops.

The life of a Roman legionary was hard. Besides strict discipline, rigorous training, and the dangers of battle, they also performed various tasks such as construction projects, policing, and tax collection. They were not constantly in combat; the majority of their service time consisted of routine military tasks such as training, patrolling, and maintaining equipment. Additionally, they played a crucial role in civil projects, such as constructing roads, bridges, ports, and public buildings. They were also deployed to establish new cities (coloniae) and improve agricultural land by clearing forests and draining swamps.

Although the pay and secondary benefits were more favorable than life as a poor farmer, conditions in the army were far from ideal. The service period originally lasted 25 years, but in some cases, soldiers could remain in service for up to 30 to 40 years. Even after their official discharge, many were sent as reservists to remote areas.

From the mid-1st century, the borders of the Roman Empire were largely stable, allowing legions to be stationed long-term in certain provinces. This affected the composition of the army. In the early imperial period, about 65% of legionaries were born in Italy, but under Emperor Hadrian (early 2nd century), this was only 8%. When auxiliary troops are also counted, only 4% of Roman soldiers were Italian, while Italians made up 12% of the total population and more than 50% of Roman citizens.

Many legionnaires came from Roman colonies in the provinces. These settlements were originally established to house veterans, giving their descendants partially Italian blood. Emperor Hadrian, for example, was born in the Spanish colony of Italica to an Italian father and presumably an Iberian mother. As the Roman borders further consolidated, sons of auxiliary veterans with Roman citizenship became an important recruitment source for legionnaires. To compensate for the declining number of Italian legionnaires, Emperor Marcus Aurelius founded the legions II Italica and III Italica in 165, presumably filled with Italian recruits through conscription.

Another problem in recruitment was the lack of citizens in some frontier provinces. In Britain, for example, there were only 50,000 Roman citizens around 100 AD out of a population of two million. This meant that the British legions largely depended on recruits from other regionss, especially from Northern Gaul. Although some historians believe that the requirement to recruit only citizens was sometimes ignored, there is evidence that this rule was strictly enforced. Known are cases where recruits were punished and dismissed after it was discovered they had falsified their citizenship. An exception was made for sons of legionnaires. Officially, legionnaires were not allowed to marry until the 3rd century, but many had long-term relationships and children. Since these children were legally illegitimate, they could not inherit their fathers' citizenship. Nevertheless, they were often recruited and presumably received Roman citizenship upon their enlistment.

Despite the harsh conditions and long service time, the Roman army had attractive benefits. Under Emperor Augustus, a legionary earned 225 denarii per year. Initially, auxiliary troops received less, but by 100 AD, this difference had largely disappeared. Although Emperors Domitian, Septimius Severus, and Caracalla raised the pay several times, this mainly compensated for inflation. Moreover, deductions were made for food and equipment, leaving a legionary with only around 115 denarii and an auxiliary troop 78 denarii.

In addition to their salary, soldiers received periodic bonuses on special occasions, such as the accession of a new emperor. After their service, legionaries received a severance payment equivalent to 13 years' salary, enabling them to buy land. For auxiliary troops, Roman citizenship was an important reward: not only they, but also their children received this status upon discharge. Additionally, the army offered opportunities for promotion: one in twenty soldiers could achieve a higher rank, increasing their pay by 50 to 100%.

Despite the low salary, these benefits offered a livelihood security, especially compared to the poverty many farmers lived in. This explains why many joined voluntarily. For poor farmers' sons, a steady military salary was more attractive than the hard farm work without any security. Often, a family had no choice but to send a son into the army to survive.

Although the army provided material security, there was frequent dissatisfaction with the pay and working conditions. One of the largest uprisings took place in 14 AD, when soldiers complained about the long service time and their poor wages. The demands included a wage increase from 2.5 to 4 sesterces per day and a shorter service period. Emperor Tiberius initially agreed but later withdrew the increase because it was too expensive. Ultimately, the real wage remained at the same level for centuries.

During these and other uprisings, frustration also emerged over the additional costs soldiers had to incur. They had to pay for clothing, weapons, and bribes to avoid unpleasant tasks themselves. Moreover, in addition to their military duties, they performed a lot of heavy work, such as digging trenches, collecting wood, and constructing roads and civil architecture.

In addition to the ordinary soldiers, there were many specialists within the army. For example, there were blacksmiths who repaired weapons and armor, carpenters who maintained wagons and wooden structures, and medics who worked in military hospitals. Some soldiers were even deployed as bath attendants or brewers, although it is uncertain whether these functions were performed by military personnel or hired civilians. Although specialists were paid the same as ordinary soldiers, they were exempt from heavy tasks, allowing them to focus entirely on their craft.

The soldiers in the Roman army came from polytheistic pagan societies and had considerable freedom in their religious practices within the Roman system. Certain religions were banned by the Roman authorities because they were incompatible with the Roman order and society. Christianity is the most famous of these.

In the later period of the Principate, Eastern mystery cults became increasingly popular within the army. These cults included secret rituals that were accessible only to initiates. The most popular cult among the soldiers was Mithraism, a religion that contained elements of Persian Zoroastrianism. The rituals and ideals of Mithras aligned well with the military values of camaraderie, courage, and loyalty, making the cult particularly attractive to soldiers.

Regarding the written documents from that time, such as the Vindolanda tablets, it appears from these texts that all documents were written by officers. Probably the lower ranks were illiterate. The language used was always Latin, usually of a reasonable level. Most authors were Gauls, Britons, or Germans, who had Celtic or Germanic as their native language, but they even wrote to their relatives in Latin. This does not mean that they no longer spoke their native language, but that these languages had not developed a written form. The letters also show that soldiers maintained friendships not only within their own regiment but also with soldiers from other regiments and even legions. 

From Augustus onwards, the emperor was deified. It was required for the entire army to worship the emperor as a god. The imperial cult was seen by the Romans as a way to affirm loyalty to the emperor, just as modern societies use an oath of allegiance. It was mandatory for all peregrini to make a burnt offering to the image of the reigning emperor at least once a year. Certificates were issued to prove compliance with this obligation. Refusal to do so was considered treason and punished by death. Parades were held on imperial birthdays, during which the images of the reigning emperor and deified previous emperors were greeted and offerings were made by the prefect of the regiment.

All types of soldiers were required to participate in various Roman religious rituals held at fixed times of the year by their regiment. These rituals included religious parades in honor of the main Roman gods, such as Jupiter, the chief god of the Roman pantheon. Many altars and tombstones dedicated by the army bear the inscription IOM, which stands for Iovi Optimo Maximo ("to Jupiter the Best and Greatest"). Other important gods worshipped were Mars, the god of war, and Minerva, the goddess also associated with war. These parades were accompanied by animal sacrifices and feasts. The prefect also served as the high priest because Indo-European religions did not distinguish between the political and religious class. This practice was also common among the Celts and Germans.

Outside the regiment ceremonies, soldiers worshipped a wide range of lesser gods. These gods can be divided into three categories: the Roman gods, their own native gods such as the Thracian Heros, often depicted on the tombstones of Thracian veterans as a mounted warrior spearing a beast or human on the ground, and the local gods of the province in which they served, such as the cult of Coventina in Britain. Coventina was a British nymph associated with springs, and several dedications to her have been found, for example, from the garrison of the fort in Carrawburgh, located on Hadrian's Wall.

One of the most well-known later cults was that of Sol Invictus "The Unconquered Sun," which was declared the official military cult by Emperor Aurelian (270-275 AD). This remained the official cult until the time of Constantine I. Mithraism was the most popular religion among Roman soldiers.   

The Roman army had a short command structure, in which the legati (legion commanders) reported directly to the provincial governor, who in turn reported to the emperor. Lower officers, the principales, were comparable to non-commissioned officers and earned up to twice the salary of a regular soldier. Centurions, who led small units, earned much more, and the primus pilus was even elevated to knight. In the Roman hierarchy, there were only four levels between the emperor and the soldiers. Governors had much autonomy, while the emperor had limited control over the army due to slow communication and a lack of intelligence. Centurions and decurions were the backbone of the legion and gave daily orders to their troops. 

The legions often carried titles indicating their origin or victories, and some regiments received honorary titles for proven loyalty.

Each tactical unit in the Roman army had its own standard, carried by a dedicated bearer and of great practical and symbolic importance. The signum was the standard of a centuria, while a vexillum was a square flag for cohorts and detachments. The most important standard was the aquila, a gilded eagle embodying Roman military prestige in the symbolism of the god Jupiter. Later, legions added portraits of emperors and dragon standards. For legionaries, their field signs symbolized the deification of the warrior class as we explained in the first blog.

The loss of a standard meant great disgrace. Individual bravery was rewarded with medals (falerae) and crowns, while regiments received distinctions such as torquata or armillata.

In the 2nd century, there is evidence of fabricae (weapon factories) within legionary bases and even in much smaller auxiliary forts, primarily staffed by the soldiers themselves. However, unlike the late Roman army of the 4th century and later, there is no evidence, literary or archaeological, of fabricae outside military bases and staffed by civilians during the principate.

Legions were supplied with weapons and equipment from various fabricae. Additionally, equipment was reused when a legionary was killed or retired. This resulted in legionaries being equally equipped, but the composition of a cohort was not uniform.

The lorica hamata was a short type of chainmail shirt with an extra layer on the shoulders to provide additional protection against blows from above. 

In addition to the lorica hamata, legionaries between the 1st and 3rd centuries AD also wore the lorica segmentata. This armor consists of several plates fastened together with leather straps. Modern tests have shown that the lorica segmentata offered better protection against weapon and projectiles than the lorica hamata or squamata. However, the lorica segmentata is less comfortable than the lorica hamata and requires more maintenance. Although the lorica segmentata was widely worn until the 3rd century, the lorica hamata remained the most prominent form of body armor for the Roman legionary. Legionaries sometimes also wore the lorica squamata.

During the late republic and early reign of Emperor Augustus, the Celtic Montefortino helmet was still in use. Additionally, until around 70 AD, the bronze Coolus helmet (Hagenau) was used. After the Gallic wars, the steel galea helmets (Weisenau) that offered better protection were developed. Both continued to be worn by legionaries into the 1st century AD. The purpose of these innovations was to enhance protection without hindering the soldier's senses and mobility. These helmets were equipped with cheek plates, a neck guard, and an upright ear guard so that the legionary's hearing was not obstructed. 

The scutum was already used by the legionaries of the late republic. During the Imperial era, this shield became shorter, approximately 107 cm long, and the oval top and bottom disappeared. The shield was now rectangular and protected the shape of the body. In the middle, the scutum had a shield boss, behind which the handle was located. The shield boss could also be used to thrust. 

The well-known sword of the Romans, the gladius, was adopted from the Iberians after the 1st Punic War. The first Roman type used was the gladius hispaniensis. Later, shorter types were introduced such as the gladius Mainz (13 BC - 200 AD), the Fulham (25 - 100 AD) and the Pompeii (0-200 AD)

As a secondary weapon, the legionnaires carried a pugio. These daggers were adopted from the Iberians during the Punic Wars. The daggers were ideal for use when there was little room to draw a gladius or when legionnaires were attacked during an ambush. The pugio appears to have been primarily used in the northwest of the Roman Empire. Possibly as a response to the ambush tactics employed by the Germans and Celts. 

Legionnaires were equipped with the developed version of the pilum, a heavy javelin used by Roman legionnaires as early as the late republic. By the end of the 1st-beginning of the 2nd century, the pilum was equipped with a bulge at the base of the head. This was possibly for balance or more penetration power. During the Republic, legionnaires were equipped with two pila, but during the principate, they seem to have carried only one pilum. Modern tests have shown that the effective range of this javelins was approximately 15 m. 

What is known about the tactics of the Imperial Era is largely speculative, as no detailed manuals have survived and the accounts of battles are often vague. In open battles, the Romans typically used a system of multiple lines, ensuring reserves were available. Reserves were essential as they both bolstered the morale of the frontline and added fresh troops to push the enemy further back. The commanders were positioned behind the frontline to determine when and where to deploy the reserves. This was done carefully: deploying too early would have no effect and exhaust the troops, while waiting too long could lead to a collapse of the frontline and panic in the army.

Fights began with both lines marching towards each other for a man-to-man combat. While enemies often tried to demoralize with shouting and other noises, the Romans marched in silence. Once the enemies were about 10 to 15 meters away, the legionaries threw their pilum at the enemy formation and attacked, accompanied by loud shouting and trumpet blasts. This sudden change in behavior by the Romans, combined with a pilum volley, often inflicted significant damage on the enemy's morale. If the enemy was broken, the Romans pursued them aggressively, often led by the cavalry, to inflict as many casualties as possible and force the enemy into submission or instill fear for future battles with the Romans.

Large battles were rare, however, and many Roman armies were engaged against guerrilla actions and sieges. During sieges, the Romans relied on their artillery. This is evident during the Jewish revolt, where Vespasian in 68 AD used at least 350 artillery pieces, along with 7,000 auxiliary archers to bombard the enemy fortifications daily. Two years later, during the siege of Jerusalem by Titus, he reportedly deployed 700 artillery pieces. This large amount of projectiles protected the legions moving towards the walls of the besieged city. The famous testudo ("tortoise") formation was used to protect the advancing legions: the front row held the shields so that they overlapped, protecting most of the body. The rear rows raised their shields above their heads, creating a shield roof over the entire unit. The soldiers on the sides held their shields sideways. This formation, along with others, was used to attack the walls of besieged settlements.

During the first two centuries of the Roman Empire, the Roman Empire experienced its best period. The army, becoming increasingly advanced after the 1st Punic War, was further perfected around this time. The expansion strategy combined with integrating conquered peoples as auxiliary troops provided a constant economic and military boost. Under Emperor Trajan in 117 AD, the Roman Empire was at its largest.