Military of ancient Rome

Roman soldiers on the cast of Trajan's Column in the Victoria and Albert Museum, London

At its territorial height, the Roman Empire may have contained between 45 million and 120 million people.[3] Historian Edward Gibbon estimated that the size of the Roman army "most probably formed a standing force of three hundred and seventy-five thousand men"[4] at the empire's territorial peak in the time of the Roman emperor Hadrian (r. 117–138). This estimate probably included only legionary and auxiliary troops of the Roman army.[4] However, Gibbon states that it is "not... easy to define the size of the Roman military with any tolerable accuracy". In the late imperial period, when vast numbers of foederati were employed by the Romans, Antonio Santosuosso (2001) estimated the combined number of men in arms of the two Roman empires numbered closer to 700,000 in total (not all members of a standing army), drawing on data from the Notitia Dignitatum. However, he notes that these figures were probably subject to inflation due to the practice of leaving dead soldiers "on the books" to continue to draw their wages and ration. Furthermore, it is irrespective of whether the troops were raised by the Romans or simply hired by them to fight on their behalf.[5]

Relief scene of Roman legionaries marching, from the Column of Marcus Aurelius, Rome, Italy, 2nd century AD

Initially, Rome's military consisted of an annual citizen levy performing military service as part of their duty to the state. During this period, the Roman army prosecuted seasonal campaigns against largely local adversaries. As the extent of the territories falling under Roman suzerainty expanded, and the size of the city's forces increased, the soldiery of ancient Rome became increasingly professional and salaried. As a consequence, military service at the lower (non-staff) levels became progressively longer-term. Roman military units of the period were largely homogeneous and highly regulated. The army consisted of units of citizen infantry known as legions (Latin: legio) as well as non-legionary allied troops known as auxiliary. The latter were most commonly called upon to provide light infantry or cavalry support.

Military service in the later empire continued to be salaried yearly and professionally for Rome's regular troops. However, the trend of employing allied or mercenary troops was expanded such that these troops came to represent a substantial proportion of Rome's forces. At the same time, the uniformity of structure found in Rome's earlier military forces disappeared. The soldiery of the era ranged from lightly armed mounted archers to heavy infantry, in regiments of varying size and quality. This was accompanied by a trend in the late empire of an increasing predominance of cavalry rather than infantry troops, as well as an emphasis on more mobile operations.

The British historian Peter Heather describes Roman military culture as being "just like the Marines, but much nastier".[6] The army did not provide much social mobility, and it also took quite some time to complete one's service. The pay was not the best for the time but could be remedied by advance in rank, loot from wars, and additional pay from emperors. Also, the army did provide a guaranteed supply of food (many times soldiers had to pay for food and supplies), doctors, and stability. In the legions of the Republic, discipline was fierce and training harsh, all intended to instill a group cohesion or esprit de corps that could bind the men together into effective fighting units. Unlike opponents such as the Gauls, who were fierce individual warriors, Roman military training concentrated on instilling teamwork and maintaining a level head over individual bravery − troops were to maintain exact formations in battle and "despise wild swinging blows"[7] in favor of sheltering behind one's shield and delivering efficient stabs when an opponent made himself vulnerable.

Loyalty was to the Roman state but pride was based in the soldier's unit, to which was attached a military standard − in the case of the legions a legionary eagle. Successful units were awarded accolades that became part of their official name, such as the 20th Legion, which became the XX Valeria Victrix (the "Valiant and Victorious 20th").

Of the martial culture of less valued units such as sailors, and light infantry, less is known, but it is doubtful that its training was as intense or its esprit de corps as strong as in the legions.

Literacy was highly valued in the Roman military, and literacy rates in the military far exceeded that of the Roman society as a whole.[8]

Roman coins grew gradually more debased due to the demands placed on the treasury of the Roman state by the military.

Although early in its history, troops were expected to provide much of their equipment, eventually, the Roman military became almost entirely funded by the state. Since soldiers of the early republican armies were also unpaid citizens, the financial burden of the army on the state was minimal. However, since the Roman state did not provide services such as housing, health, education, social security, and public transport that are part and parcel of modern states, the military always represented by far the greatest expenditure of the state.[9]

During the time of expansion in the Republic and early Empire, Roman armies had acted as a source of revenue for the Roman state, plundering conquered territories, displaying the massive wealth in triumphs upon their return and fuelling the economy[10] to the extent that historians such as Toynbee and Burke believe that the Roman economy was essentially a plunder economy. Nathan Rosenstein has questioned this assumption, indicating that Rome ran the majority of its campaigns in the 2nd century BC at a loss and relied on rare windfalls such as Aemilius Paullus' campaign in the east in 168 BC to make up the cost of war.[11] Regardless, after the empire had stopped expanding in the 2nd century AD, this source of revenue dried up; by the end of the 3rd century AD, Rome had "ceased to vanquish".[12] As tax revenue was plagued by corruption and hyperinflation during the Crisis of the Third Century, military expenditures began to become a "crushing burden"[13] on the finances of the Roman state.[14] It now highlighted weaknesses that earlier expansion had disguised. By 440 AD, an imperial law frankly states that the Roman state has insufficient tax revenue to fund an army of a size required by the demands placed upon it.[15]

Several additional factors bloated the military expenditure of the Roman Empire. First, substantial rewards were paid to "barbarian" chieftains for their good conduct in the form of negotiated subsidies and the provision of allied troops.[16] Secondly, the military boosted its numbers, possibly by one third in a single century.[9] Third, the military increasingly relied on a higher ratio of cavalry units in the late empire, which were many times more expensive to maintain than infantry units.[17]

As military size and costs increased, new taxes were introduced or existing tax laws reformed in the late empire to finance it, even though more inhabitants were available within the borders of the late empire, reducing the per capita costs for an increased standing army was impractical. A large number of the population could not be taxed because they were slaves or held Roman citizenship, both of which exempted them from taxation.[18] Of the remaining, a large number were already impoverished by centuries of warfare and weakened by chronic malnutrition. Still, they had to handle an increasing tax rate[19] and so they often abandoned their lands to survive in a city.[13]

Of the western empire's taxable population, a larger number than in the east could not be taxed because they were "primitive subsistence peasant[s]"[13] and did not produce a great deal of goods beyond agricultural products. Plunder was still made from suppressing insurgencies within the empire and on limited incursions into enemy land. Legally, much of it should have returned to the imperial purse, but these goods were simply kept by the common soldiers, who demanded it of their commanders as a right. Given the low wages and high inflation in the later Empire, the soldiers felt that they had a right to acquire plunder.[20][21]

Locations of Roman legions, 80 AD

The military capability of Rome – its preparedness or readiness – was always primarily based upon the maintenance of an active fighting force acting either at or beyond its military frontiers, something that historian Luttwak refers to as a "thin linear perimeter.[22] This is best illustrated by showing the dispositions of the Roman legions, the backbone of the Roman army. Because of these deployments, the Roman military kept a central strategic reserve after the Social War. Such reserves were only re-established during the late empire when the army was split into a border defense force and mobile response field units.

The Roman military was keen on the doctrine of power projection – it frequently removed foreign rulers by force or intimidation and replaced them with puppets. This was facilitated by the maintenance, for at least part of its history, of a series of client states and other subjugate and buffer entities beyond its official borders, although over which Rome extended massive political and military control. On the other hand, this also could mean the payment of immense subsidies to foreign powers[23] and opened the possibility of extortion in case military means were insufficient.

The empire's system of building an extensive and well-maintained road network, as well as its absolute command of the Mediterranean for much of its history, enabled a primitive form of rapid reaction, also stressed in modern military doctrine, although because there was no real strategic reserve, this often entailed raising fresh troops or withdrawing troops from other parts of the border. However, border troops were usually very capable of handling enemies before they could penetrate far into the Roman hinterland.

The Roman military had an extensive logistical supply chain. There was no specialised branch of the military devoted to logistics and transportation, although this was to a great extent carried out by the Roman navy due to the ease and low costs of transporting goods via sea and river compared to overland.[24] There is archaeological evidence that Roman armies campaigning in Germania were supplied by a logistical supply chain beginning in Italy and Gaul, then transported by sea to the northern coast of Germania, and finally penetrating Germania via barges on inland waterways. Forces were routinely supplied via fixed supply chains, and although Roman armies in enemy territory would often supplement or replace this by foraging for food or purchasing food locally, this was often insufficient for their needs: Heather states that a single legion would have required 13.5 tonnes of food per month, and that it would have proved impossible to source this locally.[25]

For the most part, Roman cities had a civil guard used for maintaining peace. Due to fear of rebellions and other uprisings, they were forbidden to be armed at militia levels. Policing was split between the city guard for low-level affairs and the Roman legions and auxiliary for suppressing higher-level rioting and rebellion. This civil guard created a limited strategic reserve, one that fared poorly in actual warfare.

The massive earthen ramp at Masada, designed by the Roman army to breach the fortress' walls

The military engineering of Ancient Rome's armed forces was of a scale and frequency far beyond that of any of its contemporaries. Indeed, military engineering was in many ways institutionally endemic in Roman military culture, as demonstrated by the fact that each Roman legionary had as part of his equipment a shovel, alongside his gladius (sword) and pila (spears). Heather writes that "Learning to build, and build quickly, was a standard element of training".[26]

This engineering prowess was, however, only evident during the peak of Roman military prowess from the mid-republic to the mid-empire. Before the mid-republic period, there is little evidence of protracted or exceptional military engineering, and in the late empire likewise, there is little sign of the kind of engineering feats that were regularly carried out in the earlier empire.

Roman military engineering took both routine and extraordinary forms, the former a proactive part of standard military procedure, and the latter of an extraordinary or reactionary nature. Proactive military engineering took the form of the regular construction of fortified camps, in road-building, and the construction of siege engines. The knowledge and experience learned through such routine engineering lent itself readily to any extraordinary engineering projects required by the army, such as the circumvallations constructed at Alesia and the earthen ramp constructed at Masada.

This engineering expertise practiced in daily routines also served in the construction of siege equipment such as ballistae, onagers and siege towers, as well as allowing the troops to construct roads, bridges, and fortified camps. All of these led to strategic capabilities, allowing Roman troops to, respectively, assault besieged settlements, move more rapidly to wherever they were needed, cross rivers to reduce march times and surprise enemies, and to camp in relative security even in enemy territory.

In its purest form, the concept of strategy deals solely with military issues. However, Rome is offered by Edward Luttwak and others as an early example of a state that possessed a grand strategy which encompassed the management of the resources of an entire nation in the conduct of warfare. Up to half of the funds raised by the Roman state were spent on its military, and the Romans displayed a strategy that was more complicated than simple knee-jerk strategic or tactical responses to individual threats. Rome's strategy changed over time, implementing different systems to meet different challenges that reflected changing internal priorities. Elements of Rome's strategy included the use of client states, the deterrent of armed response in parallel with manipulative diplomacy, and a fixed system of troop deployments and road networks. Luttwak states that there are "instructive similarities" between Roman and modern military strategy.[28]

Rome would rely on brute force and sheer numbers when in doubt. The soldiers were trained to memorize every step in battle, so discipline and order could not break down into chaos. They were largely successful because of this.

General set up of ancient Roman military hospital.

The expansion of the Roman Empire was achieved through military force in nearly every case. Roman culture as a whole revolved around its military for both expansion and protection.[29] Geographic areas on the outskirts of the empire were prone to attack and required heavy military presence. The constant barrage of attacks and the increase of expansion caused casualties. Due to attack there was a need for specialized medical care for these armies in order to keep them in operational status.[30] The specialized form of care however, was not created until the time of Augustus (r. 27 BC – AD 14).[30] Prior to this there is little information about the care of soldiers. It is assumed soldiers were self-reliant, treating their own wounds and caring for other ailments encountered.[31] They would also turn to civilians for help throughout the villages they would come across. This was considered a custom of the time, and was quite common for households to take in wounded soldiers and tend to them.[31] As time progressed, there was an increase in care for the wounded as hospitals appeared. The idea was held by the Romans that a healed soldier was better than a dead one and a healed veteran was better than a new recruit.[32]

With the need for soldier health a growing concern, places for the sick to go in the army were starting to show up. Dates ranged from AD 9 to AD 50, but this is when the first evidence of hospitals was seen in archeological remains.[30] These hospitals were specific places for only military members to go to if they were injured or fell ill. Similar hospitals were set up for slaves in areas where slaves were used in large numbers. Military hospitals were permanent structures set up in forts. These buildings had clear patient rooms and were designed to accommodate large numbers of soldiers.[30] The size of these hospitals varied based on their location. Some of the large facilities, such as the hospital in Hod Hill England, was large enough to accommodate roughly 12% of the force within the hospital. In more stable areas such as Inchtuthil in Scotland, there was room for as little as 2% of the force within the hospital. In areas with more conflict, there were larger medical facilities as they saw more casualties.[30] These hospitals were solely designed for the use of the military. If a civilian fell ill or needed surgery they would likely go to the physician's home and stay, not a hospital.[30] Prior to these permanent structures there were tents set up as mobile field hospitals. Soldiers suffering from severe wounds were brought to these for treatment. These were quickly assembled and disassembled as the army moved. The tents served as a precursor for the permanent structured hospitals.[31] These permanent hospitals and mobile treatment centers were a relatively new concept in this time period.

Capsarii tending to injured soldiers depicted on Trajan's Column

Doctors serving in the army were considered to be a member of the military. Just like everyone else they would take the military oath and be bound by the military law. They would also start among the lower fighting ranks. Even though they took the military oath and were among the lower ranks it did not mean they would be fighting among the masses.[33] These doctors were not always professionals or career physicians. Oftentimes they were slaves who were forced into that career.

The capsarii were a group that also treated wounded soldiers on the battlefield. These men were not trained physicians even though they played the role of one. Typically they were soldiers who demonstrated they had knowledge in wound treatment and even simple surgical techniques.[34] These men were used before the actual trained doctors were largely implemented. Physicians got their knowledge from experience and information being passed down from person to person. Likely they never used medical texts, as it was not commonplace even in the civilian field.[34] Generals and emperors were exceptions, as they would typically have their physicians with them. This was a common occurrence as emperors such as Marcus Aurelius employed famous physicians such as Galen. There were also physicians among the ranks of the Roman soldiers.[32]

With any large number of people being in close quarters, there was a constant threat of disease. When one individual in a large group gets sick with a communicable disease, it spreads to others very quickly. This premise remains true even today in the modern military. The Romans recognized the difference between disease and wounds, each requiring separate treatment.[33] Drainage of excess water and waste were common practices in camps as well as the permanent medical structures, which come at a later date. As the medical corps grew in size there was also specialization evolving. Physicians surfaced that specialized in disease, surgery, wound dressing and even veterinary medicine.

Veterinary physicians were there to tend to livestock for agricultural purposes as well as combat purposes. The Roman cavalry was known for their use of horses in combat and scouting purposes.[35] Because of the type of injuries that would have been commonly seen, surgery was a somewhat common occurrence. Tools such as scissors, knives and arrow extractors have been found in remains.[36] In fact, Roman surgery was quite intuitive, in contrast to common thought of ancient surgery. The Roman military surgeons used a cocktail of plants, which created a sedative similar to modern anesthesia. Written documentation also showed surgeons used oxidation from a metal such as copper and scrape it into wounds, which provided an antibacterial effect; however, this method was most likely more toxic than providing an actual benefit.[37] Doctors had the knowledge to clean their surgical instruments with hot water after each use. Wounds were dressed, and dead tissue was removed when bandages were changed. Honey and cobwebs were items used to cover wounds, and have even been shown today to increase healing.[37] Because of the wide array of cases, it was not uncommon for surgeons to begin their careers in the army to learn their trade. Physicians such as Galen and Dioscorides served in the military. Most major advancements in knowledge and technique came from the military rather than civil practice.[37]

Diet was an issue that is often discussed through this time, as an aspect of medical care. Since our idea of modern technology did not exist, the diet was a simple way for Romans to attain a healthy life. This remains true in the Roman military as the soldiers required appropriate nutrition in order to function at high activity levels.[38] Because of the number of the people requiring food, there were unique circumstances in the acquisition of food. During a campaign, the soldiers would often forage food from their enemy's land. In fact, as part of the standard kit, Roman soldiers would carry a sickle, which would be used to forage food. They would carry a three-day ration of food in case they were in a situation where foraging was not available.[39] This would largely consist of items such as wheat and barley.

During a time of peace, the Roman army would have had a typical diet consisting of bacon, cheese, vegetables, and beer to drink. Corn is mentioned in their works as well, however; this was a common term that was applied to their use of grain. The Roman use of the term corn is not to be confused with maize, which did not come to Europe until the discovery of the New World. Items such as poultry and fish were also likely part of the standard diet. The soldier was given a ration, which was taken from his pay.[39] This shows that the soldiers were well-fed in times of peace. If the soldiers were well fed, they were healthier and able to maintain a high level of physical activity, as well as to stave off disease. The disease is easier to prevent rather than treat. This idea holds in the event a fort was under siege; certain food items were rationed such as poultry. The reasoning behind this was that poultry was very inexpensive to maintain and in the event of a siege. It was also noted that poultry had benefits for those who were sick. This demonstrates the idea was present that the army needed to maintain the health of its members regardless of circumstances.[39] These discoveries were made while looking at the remains of Roman military sites. By excavating these sites and looking at fecal matter found, scientists were able to determine what was eaten.[40] It is a simple fact that poor diet negatively affects a military's combat readiness. The variety of food found shows the Romans were not focused on just caloric intake, as they knew a variety of food was important to health.[38]

By the time of Trajan (r. 98–117), the medical corps was well on the way to being an organized machine. At this time, physicians were attached to nearly every army and navy unit in all the Roman military. By this time the army was massive, consisting of twenty-five to thirty legions, each of which contained nearly 6,000 men. Each one included both soldiers and physicians.[37] Despite these large numbers there was still no formal requirements for being a physician.[33] At this point all physicians were either self-taught or learned their trade through an apprenticeship. Despite this, there was an attempt at organization, as the army did have a medical manual that was passed out to its physicians. The medici were used on both the front line as emergency care providers and in the rear as the main physicians. The capsarii'' were mainly used as the front line care providers and bandages, but also assisted the medici behind the lines.[37]

Romans received their medical knowledge largely from the ancient Greeks. As Rome started to expand, it slowly embraced the Greek culture, causing an influx of medicinal information in Roman society.[41] Because of this influx, it allowed this knowledge to become the foundation of all Western medical tradition. The Greek theories were kept alive and their practices continued well into the future.[41] This knowledge was also the foundation used in military medicine since it contained the overarching ideas of their medical knowledge. As time progressed these medical texts would be translated into Arabic and then back into Latin as the flow of information changed. Based on this, one can presume that some of the information in these texts has been lost in translation. Despite this, scholars are still able to establish a clear picture of what military medicine was like during the reign of the Roman Empire.