The Roman Army

The Roman army was one of the finest fighting machines the world has ever known. Beginning as a group of citizen soldiers who provided their own arms and defended the early city of Rome in times of emergency, the Roman army grew to become one of the largest professional fighting forces the world had ever seen. In later years, the enormous bureaucracy that governed and supplied the Roman army would grow to rival those of modern days. During its 1,200 year existence in the West and 2,200 year history through Byzantine times, this army underwent numerous major transformations and smaller changes. Some changes were brought about by new advances in weapons, some because more effective tactics were developed, and some occurred because the pressing needs of the empire required change. One change that continued right up through the end was the increasing use of barbarian troops and officers. In the years before the end of the Roman Empire in the West, the army was composed of almost all barbarian troops who were defending an increasingly weak empire against their own relatives. If there was ever a conflict of interest, this surely would be one! 
The legion was the largest unit in the Roman Army. Originally, a legion consisted of from 5000 to 5500 men, but seldom was a legion ever at its full strength. More often, a legion consisted of 4000 to 4800 combat ready troops. 
Each legion was divided into cohorts of about 600 men each. Sometimes the number one cohort was twice the size of the others. The number one cohort was usually assigned to administrative and supply duties. 
The basic battlefield unit was the century, originally composed of 100 men. This Latin word means a unit of one hundred and it is the same word we use today for a unit of one hundred years. Most legions had less than the full number of troops and usually contained between eighty and one hundred men, and sometimes even less than that. They were led by a non-commissioned officer called a centurion. There were different grades of centurions. Some were men who had only been in the army a few years and whose rank was roughly equivalent to a sergeant. Others were twenty year or more veterans and might be likened to a commissioned or staff officer in today's United States or British army. 
Another unit that appeared from time to time was the maniple. A maniple consisted of two centuries, giving a cohort of three maniples or six centuries. 
During the Third Century, the emperor Gallienus introduced a fast, mobile striking force mounted on horseback. Before this time, Roman officers and soldiers sometimes rode horses to the scene of the battle but dismounted to fight. Gallienus' troops were real cavalry in that they fought from horseback as well. 
Diocletian and Constantine officially divided the Roman army into the COMITATENSIS, or mobile fighting force, and the LIMITANEI or troops assigned to guard the frontier. This pattern was kept and maintained until the end of the Western Roman Empire. The idea behind the COMITATENSIS was to have a highly mobile field army that could be ready to go anywhere in the empire at a moment's notice and be on the scene of trouble in two to three weeks. 
Auxiliary units began to be used more and more from the reign Of Septimius Severus in the early Third Century onward. These included lightly armed cavalry "wings", units of mounted archers (SAGITTARII), lancers, heavily armored cavalry (CATAPHRACTII), and other specialized units. Julius Caesar used skilled slingers from the Balearic Islands and Batavii (from near modern Belgium) who were strong swimmers and could withstand cold water. They made excellent special agents and infiltrators. Roman army organization, tactics, and strategy is the subject of countless books. The Roman Army still holds the fascination of military historians today, as more books are being written all the time as they have for over two thousand years. 
Starvation was a very common strategy used in the ancient and medieval worlds to bring an otherwise strongly defended city or fort to the point of surrender. The besieging army would surround the city, cutting off all routes whereby it might be resupplied with food and water. If the king or other ruler who governed the city planned ahead, the defenders could bring livestock and supplies of grain within the walls. Often cities were built so that a spring or good well was enclosed within the walls. In these cases, the besieging army would have a difficult time starving the city into surrender. The Romans had a few other tricks up their sleeves when confronted by a stoutly defended and well supplied city. They built siege towers from wooden poles bound together with leather from the top of which they could rain arrows down on the unfortunate defenders. They also used siege artillery such as ballistas, onagers, and catapults to throw stones or short, thick arrows known as bolts over the walls at the defenders. The Romans were not above using some dirty tricks, too. balls of flaming pitch and burning sulfur were used by both attackers and defenders. Sometimes, the besiegers would cut the heads off slain soldiers who were known to be relatives of those holding out behind the walls. The severed heads were allowed to ripen in the hot sun until they had reached a very smelly and offensive condition. They were then pitched over the walls with catapults to fall amongst the hapless population of the besieged city. Another tactic used to terrorize and demoralize the population of a besieged town over a period of days or weeks was to mount the heads on pikes. These trophies were then set up in full view of the defenders and allowed to stay there until they became black and leathery. To add to the discomfort of the people holed up behind the walls, the besieging troops often made these heads of the defenders' former family members the object of scorn and desecration. 
Pulled by specially bred horses, chariots like the one shown on this coin served the Romans as "mechanized infantry" and provided a fast, reasonably well armoured platform for mobile archery strikes. They had been used by much earlier civilizations including the Assyrians, Hittites, and Egyptians who employed them in war and also as a suitably triumphant looking conveyance for their rulers while on parade before their people. Chariots and the horses that pulled them also served as a psychological weapon, striking fear into the hearts of enemy soldiers. Ancient chariots were attached to a type of harness that forced the horse to pull with his neck rather than his shoulder as is the case with modern harness. This was injurious to the horse, often choking the animal and certainly reducing the weight of load he could have pulled had he been fitted with a better collar. It has been speculated that the reason so many horses depicted in ancient art are shown in the act of rearing up and pawing the air with their front hooves is that they were reacting against the harness rather than displaying their bellicose fierceness and raw animal power! 
The onager, meaning "wild ass" in Latin, was the name given to the small Roman catapult used for hurling medium sized stones at enemy troops and over the walls of fortified towns. Like the ballista and the large siege catapult, the onager was powered by a spring made of a combination of twisted leather thongs and heavy arms made of springy wood or bone layered with wood. The operator would use a pole in a windlass to wind up the onager, which had a ratchet so that the soldier operating it could move the pole to another socket in the windlass. When the trigger mechanism was released, the wound up spring would swing up a long arm at the end of which was a basket holding a good sized stone. The secret of how the Romans were able to make such good springs from hide and bone from animals and wood from trees has been lost. Some historians who have investigated the scientific discoveries of the ancient world believe that the Greeks had developed a springy alloy of bronze unlike the spring bronze used in some machine parts today, but it was only used in experimental catapults. There is no evidence that the Romans utilized metal springs in any of their siege engines. 

Like any modern army the Romans had their main body of infantry troops and also their auxiliary troops, their cavalry and mounted infantry, their bush fighters, and their desert warriors. 
Regular deductions were made from the legionary's pay to cover normal wear and replacement of his equipment, similar to the deductions made for his burial expenses and the annual camp dinner. In the case of nail money the situation was reversed and the soldier was given an allowance for worn boots. 
Beginning with the soldier's basic equipment, we have: 
Steel or Bronze Pot Helmet (Cassis). Junior officers (Optiones) and Centurions might wear protective headgear almost as highly decorated as they could afford to purchase. Most infantrymen used the stock issue helmet provided by the quartermaster's department. 
Segmented Plate Cuirass and Body Armour given the name Lorica Segmentata by modern historians, those formed of steel plate armour was riveted together securely enough to withstand sword slashes yet with enough play between the plates that the armour would flex when the legionary moved about. This type of armour was much less expensive to fabricate than the fine chain mail that was more popular amongst the legions in the East. 
The Long Curved Rectangular Shield or Scutum is probably one of the most variable of the equipment items carried by Roman legionaries throughout the 1100 year existence of the Roman army in the West and the 1000 additional years during which Romaion or Byzantine military tradition held in the East. During the last century of the Republic and the first century of the Empire, the scutum was in general use. Even so many units preferred either a large or a small round shield, and oval shields became popular during the later Roman Empire (AD 330 to 600). One advantage of this type is that they could be held edge to edge to form a Testudo, which provided armoured protection with good coverage for a group of men. 
Leather walking sandals These did not change much during the course of historical antiquity. Their open design permitted the feet to breathe on long marches. They were relatively easy to make and repair, unlike the formed leather boots adopted by European armies much later. It was the excessive wear caused by so much forced marching that led the mutinous legions to demand nail money upon the accession of the Emperor Tiberius. The money would ostensibly be used to replace the worn out sandals. 
The long red military cloak kept the legionary warm in colder climates and helped keep the rain off during inclement weather. Its red colour was also probably intended to identify him as a Roman in the dust and confusion of battle and inspire fear into the hearts of his enemies. The sight of a massive red juggernaut headed relentlessly in their direction must have clamped a cold claw of fear around the heart of many defenders of rebellious cities and sapped their will to fight. 
Short thrusting Sword (Gladius) Roman battle tactics called for close - ordered, disciplined troops fighting as a team as opposed to individual heroics as used by many of their enemies. There were no heroes or champions in Roman armies, only trained soldiers, standing shoulder to shoulder for twenty minutes at a time, methodically killing their opponents. When an occasional lucky stroke by a barbarian warrior brought down a Roman soldier, another of his brethren immediately stepped forward to fill his spot. When the twenty minute period of killing was finished, the legionary fell back and rested to be replaced with a fresh man. 
These kinds of tactics called for a short thrusting sword instead of the long one used for slashing. The Roman Gladius was 18 to 24 inches in length, double edged and parallel sided. The last few inches of blade tapered to a point and the grip was terminated on the back side with a large ball shaped pommel. A short, powerful thrust going a few inches into a man was much more deadly, though less dramatic, than the wide, energy wasting slashes made by an individual warrior showboating in front of his buddies. 
Medium length Throwing Spear or Javelin (Pilum) This is another standard weapon that almost defines the Roman legionary. The medium weight iron head was connected by a long, thin neck to either an iron socket into which the wooden shaft was fitted, or the metal was extended backward into a thin tang which fitted into a socket in the wood. The main point is that the hardened head of the Pilum would penetrate the enemy shield and the soft neck would bend over. Removing the head of the Pilum from the shield would take too much time, so both Pilum and shield were then thrown away. At this point, the enemy warrior had only two and a half choices left: he could turn around and run like a rabbit, hoping that a Roman scouting party was not waiting for him to do just that. He could let out a bloodcurdling scream and go berserk like the Vikings much later and run up and try to brain one or two Romans with his sword before being skewered himself. In this case, maybe his buddies would sing sagas about him around the campfire on cold Winter evenings, telling of his brave deeds while the Romans celebrated Saturnalia in their camp, laughing about what a numb skull he was. Choice number two and a half is he could look around the battlefield for a shield not pierced by a Pilum, perhaps dropped or thrown away by one of his buddies. He could pick it up and dust it off, and walk coldly and deliberately towards the Roman lines. He could then kill two Roman soldiers, one for his fallen/fleeing buddy, and one for himself, to make up for the embarrassment of letting him get close enough to a Pilum equipped Roman soldier to get his shield pierced. 

The Testudo
Long before modern military engineers came upon the idea of using armored vehicles to protect soldiers from enemy fire, the Romans had developed armored divisions of their own. When attacking a fortified town or a heavily defended enemy position, the Roman legionaries would arrange their shields to form a box covering their heads and all sides. This tactic was called the Tetstudo, meaning tortoise in Latin. They could then advance through a hail of arrows or sling stones to overrun the enemy in his position. Moving the shields apart just enough to allow their swords to poke through, the Romans used the same stabbing technique that they found so effective in regular battle. Because they did not slash with their swords but would thrust and stab, they did not have to leave much of a space in their shield wall. It must have been a fearsome sight indeed for native warriors in Gaul or Persia or northern Thrace who were not used to the cooperation of disciplined warfare and preferred individual heroics. It was not until the coming of heavy mounted cavalry and well designed saddles with stirrups that an effective way was found to attack the Testudo.


Legion Formations

The Earliest Army

The earliest Roman army is usually described as composed of about 1,000 men per tribe drawn in 100 man levies. The soldiers were armed as Greek Hoplites and fought in a simple Phalanx. 

The 4,000 MAN Five Class Army

Tradition attributes the reorganization of the army to the sixth king, Servius Tullius, although the actual process may have taken a number of years. By the time of the war with Veii the army probably had fully developed the 5 classes. Without detailed descriptions of the army formed from the classes one can only make reasonable guesses about its composition. In this model the same number of men are assumed to have been levied from each Century, the phalanx is kept at the Greek standard of 8 ranks, and the overall army size is about 4,000. If 25 men from each Century were levied then there would have been 2,000 from the First Class, 500 from Classes II through IIII and 750 from Class V. 4,000 men in 8 Ranks will fill 500 Files. That would give the First Class 4 Ranks, Classes II through IIII one Rank each and leave 750 men in Class V for the 500 files of the last Rank. The last Rank is represented as composed of 500 men of the Fifth Class with the remaining 250 men being used as skirmishers, flankers or camp guards. In the drawing this presumed 250 man unit is not depicted. Although barely visible at this scale, the Phalanx in the drawing above is divided into separate ranks by Class. Each Class is given a different colour. Under the assumption that the Phalanx would have been somehow subdivided into smaller units, the 500 files have been divided into units of 100 files 8 ranks deep and separated by three meters (ten feet) to provide room for the phalanx to manoeuvre. Of course, the actual armies were never so nicely composed, but this configuration at least gives a reasonable starting point for visualizing the army.

The Early Livy Legion

The earliest legion is generally said to be the 45 unit legion as described by Livy and dates to the early part of the 4th century BC. The maniple consisted of two centuries of 10 files by 3 ranks. All maniples had the same number of men. In front of each Hastati maniple there were 20 skirmishers called Leves. All maniples were armed with the spear and oval shield. 

An Alternative Early Legion

Delbrück offers an alternate interpretation of the Livy legion, different from Connolly in his analysis of the Rorarii and Accensi. He works from Livy's number: 186 men "antipilani" and "sub signis." His explanation is that the Triarii were at one time called the Pilani and that the Triarii, Rorarii and Accensi were positioned behind the standards. Those behind the standards, then, were the 60 men of the Triarii; plus the 120 Rorarii attached in units of 40 men to each of the Hastati, Principes and Triarii maniples; plus the 6 Accensi, orderlies or company clerks; for a total of 186 men. He considers the Leves, the skirmishers, to be a part of the 40 man Rorarii unit assigned to each Hastati maniple. For the 10 Hastati maniples that would place some 200 skirmishers directly in front of the battle line. These are the men who would retreat through the gaps in the Hastati line. He also mentions that there may have been other skirmishers on the flanks; possibly the other 20 Rorarii of the Hastati maniples. He does not believe the Rorarii of the Principes and Triarii maniples were combat soldiers at all, but rather were unarmed assistants. The Accensi, he says, were totally misinterpreted by Livy. These were the 6 orderlies of the cohort. In muster formation the three 40 man Rorarii units would stand behind the 60 man Triarii maniples. Behind them would stand the 6 Accensi orderlies. This gives the number of 186 men as "sub Signis."

Delbrück argues against the notion that the legion actually went into battle with wide gaps between the maniples. His view is that the legion was really an articulated Phalanx with only small intervals between the maniples to allow adjustments in spacing due to irregular terrain and errors in marching. The gaps would be naturally closed by the men in the adjoining maniples at the time contact is made. If larger gaps opened whole units such as centuries or maniples of the Principes would fill in. The maniples of the Principes would have lined up on the small intervals in the Hastati. The Delbrück maniple has men on 0.91m (3') spacing both for file and rank with the centuries placed side by side. Each century has 10 files and 6 ranks. The placement of the centurions is not given. Delbrück recognizes the requirement for 1.83m (6') of fighting room for each individual given by Vegetius. However he interprets the 1.83m (6') spacing as being between adjacent ranks, not files. His method is to have alternate ranks step to the side to fill in the gaps in the rank in front. In this way there is 1.83m (6') between rank 1 and rank 3 The Delbrück maniple in battle formation had a staggered formation.

Twenty men from each Rorarii unit attached to the Hastati are depicted as skirmishers spread in a thin line in front of the legion. They would retreat through the narrow gaps between the maniples. The other twenty men of the Hastati Rorarii units may have been used as skirmishers on the flanks; they are not depicted in the schematic. The balance of the Rorarii and Accensii are placed at the bottom of the schematic to indicate that they were, in Delbrück's reconstruction, not a part of the battle and may have been left as camp guards. The Triarii maniples are comprised of two 30 man centuries aligned one behind to other to maintain a 6 Rank depth. Delbrück states that a depth of fewer than 6 Ranks would not have been an effective force and that the maniples could make up for the gap because of the distance they had between themselves and the battle lines would allow them time and space to maneuver to close the gaps if necessary.

Delbrück does not specify how wide the small gaps between maniples were, but he does allow enough for the 20 skirmishers to retreat. The model uses a spacing between maniples of 3.05m (10') which seems large enough to allow the 20 skirmishers room to retreat and small enough for a few men on either side to close the gap. Delbrück also argues that the 76m (250') spacing of the later legions is an echelon tactic introduced first by Hannibal and adopted into the Roman system by Scipio Africanus, sometime between 211 and 200 BC, probably in Spain. Prior to his innovation the three lines, Delbrück believes, would have been fairly close together, about 30m (100'). 

The 4,200-man Republican Legion

At some time after 340 BC the legion was reorganized again. It may have been about this time that 200 of the Rorarii were withdrawn, trained, armed as light skirmishers and named Velites. From this time the legion was configured with the standard 30 maniple formation. The maniple was comprised of two 60 man centuries, usually described as either 10 files by 6 Ranks or 12 files by 5 Ranks. The latter formation is used in this schematic, following Rüstow and others. In this version of the legion the large Velites units are shown aligned between the two centuries of the Triarii in the third line as they would have been during muster and, perhaps, during battle after they had retired. The centuries of the Hastati and Principes are shown aligned one behind the other. This is the classic formation as it is usually given, by Montross and Rüstow, for example.

Echelon Tactics

Delbrück credits the development of echelon tactics to Scipio Africanus, probably during his campaigns in Spain. The great advantage of echelon tactics is that it allowed the lines to operate somewhat independently. He also places the introduction of the Pilum to coincide with the new tactics. The legion of Scipio is essentially the same as the earlier legion in its overall formation with the exception that the lines are much further apart, about 76m (250'). In this schematic the Velites are shown in the skirmish position.

The 4,800-man Legion of Marius -- Cohort Tactics

A major change came at the time of Marius and is usually attributed to him, although some elements of the reorganization of the legion may have been implemented prior to Marius' reform. The nominal maniple strength was probably 160 men, divided into two centuries which most authors place one behind the other. The most likely configuration is 16 files by 10 ranks. It has the advantage of scaling down by units of 5 or ten as the maniple strength was depleted. By the time of Caesar it is clear that the cohort had become the fundamental tactical unit. He describes battle formations and troop movements in terms of cohorts and legions appear more as administrative units than battlefield tactical units. Caesar sends cohorts and groups of cohorts, not legions, on flanking manoeuvres. Since the number of men in a cohort could vary considerably the formation must have been scaleable in some consistent manner so that its fighting efficiency was not destroyed by the reduction in manpower. The typical formation, described above, uses a spacing of 0.91m (3') for the files and 1.22m (4') for the ranks; allowing for the centurion, then, the cohort would have a front of 15.85m (52'). If the three cohorts fought side by side, as is always depicted, then their combined front would have extended to 48.16m (158'). The cohort would, in essence, be a miniature phalanx, 10 ranks deep and 58 files wide.

Caesar's legions are usually described as having a strength of about 3,600 men, fewer than the full strength legion. How would the under strength legion have been configured? It seems reasonable that the cohort would be scaled down by reducing the number of files, not the number of ranks. Reducing the number of ranks would decrease the depth and hence the power of the formation. Reducing the number of files would reduce the front but retain the full power of the formation. It therefore seems most logical to retain the full 10 ranks as the depth and reduce the number of files as necessary. The drawing on the right shows two reduced centuries of 5 ranks and 12 files each. At the battle of Ilerda Caesar's forces were caught on a narrow ridge just wide enough for three cohorts in line of battle. Judson states that this ridge can could be identified in his day and was 110 meters (360') wide. The front of a 12 file cohort is 12.2m (40'), giving a three-cohort unit a front of exactly 109.73m (360'). If Judson's information is correct, it would appear to confirm this formation.

The Legion of Marius -- Alternate Formations

Delbrück does not specifically discuss the question of gaps between the cohorts of the Marian legion. He argues, persuasively I think, against the possibility of gaps in the pre-Marian legion formation in which the units and, consequently, the gaps were much smaller. To be consistent Delbrück would have to be presumed to eliminate the wider gaps in the post-Marian legion, placing the cohorts close together with only small gaps between them. The drawing below shows this legion with 7.62m (25') spaces between the cohorts for the skirmishers. The legion formation in this configuration is much more compact and has a front of only 212m (694'). If this were the legion formation then it would be a departure from the earlier legion in that the centuries would now be aligned front to back rather than side by side. In favour of this configuration are: (1) the cohort front fits Judson's information about Ilerda (assuming Judson is accurate), (2) the second century was called the posterior century, and (3) since cohorts were used as quasi-independent tactical units they may have needed the extra depth of the formation.

Against this configuration is the argument for consistency and conservatism. It can be argued that, if the centuries were aligned side by side prior to the reorganization of Marius, then it seems likely that they would have been aligned that way after Marius. The change in the position of the Posterior Century would represent a significant change in tactics, even down to details such as how and when the ranks could employ their pila. The style of fighting had evolved over a long period and may be considered to have been "optimized." That is, the tactics of the individual soldiers armed with the scutum, pilum and gladius which had been evolved to this time were probably those which best suited those weapons; major changes would probably not have been an improvement. Finally, at the level of the century, the soldiers were trained, drilled and led by their centurions who represented a conservative, in the sense "conserving," element in the army; Marius' changes were dramatic enough without also including fundamental changes in tactics at every level and the re-training which would have had to occur. If the centuries were arranged side by side to form an unbroken line, the drawing above shows how this formation may have looked, with 1.53m (5') spaces between maniples and 6.1m (20') spaces between the cohorts. It gives an overall front of 391m (1,282').

The 5,130-man Imperial Legion

During the second half of the first century AD, the size of the cohorts was increased. The regular cohort was increased in size to 480 men in six centuries of 10 files and 8 ranks each. The first cohort was enlarged to 810 men in 5 centuries of 18 files and 9 ranks. The centuries are usually represented as being arranged two deep with the maniples side by side. For the six centuries of the normal cohort this is a logical formation. For the five centuries of the first cohort the scheme does not work. If four of the centuries are aligned in a rectangle they occupy about the same space as the six centuries of the other cohorts. This would allow them to fit nicely into the overall legion formation. That would leave one extra century. An alternate formation is possible. If the legion did close gaps by aligning the maniples side by side within the cohorts to form a continuous line, then the formation may have looked something like the drawing below. The legion was a fighting unit with unique weapons, tactics and formations; and was the most successful army of the ancient world. Yet we do not understand how it functioned in some of the most basic ways. The legion's formation and tactics were changed over time and were adapted to meet local battlefield conditions. Yet there is a core understanding, an "idealized legion," which can be described. The legion incorporated its own unique characteristics; among them were: the regular use of two and three lines, division of forces into centuries, maniples and cohorts, command by Centurions, use of trumpets and standards, and the tactics of the Pilum and Gladius. 

Cadence of the march and run

The march cadence is fairly well established. The Roman militari gradu, regular march cadence, was 100 paces per minute, the quick march cadence was 120 paces per minute. The Roman foot was 0.9708 English foot. The pace was 2.5 Roman feet, 29.124". According to Upton, this is almost exactly the same as the US Army standard at the turn of the century; its pace was 30", the regular march cadence was 100 paces / minute and the quick march cadence was 120 paces / minute. The pace of the running charge is unknown, and surely varied considerably from battle to battle according to the terrain. The running pace used in the model was derived from some modern data from a variety of sources. A "pace" is the interval between left and right heel strikes, a "step" is the interval between strikes of the same foot. There are two paces to the step. The Roman soldier was running in formation, over uneven ground, carrying arms, wearing armour, and in the process both throwing his pilum and avoiding oncoming missiles. For modelling purposes I used 3 paces of 40" per second for the charge, less than runners in even long distance races but faster than a jog.

The next element to work out where in the attack the pila might have been thrown by each rank. Authors give a wide range of distances for the pilum, from a high of 27.43m (90’) to a low 7.62m (25’). One even puts it as low as 4.87m (16’) but this seems wholly unreasonable. The estimated weight of the pilum also varies widely. One author estimates the weight at 8.62kg (19 Lb.), another at 4.99kg (11 Lb.). Spears and pikes in museums, of similar length but different construction, weight between 1.59kg (3.5Lbs.) to 2.5kg (5.5 Lb.). Calculations based on an accurately drawn model and using typical densities for iron and wood give a weight of about 4.9 pounds. The weight added to imperial pila probably doubled the overall weight. Although some authors say that a throwing strap was used, most disagree. The soldier used his pilum during the last few seconds of the charge while running over uneven ground, keeping his spacing with his comrades, and dodging enemy missiles. Furthermore, he had to be able draw his sword immediately upon release or upon dropping the pilum. A throwing strap would seem like an unwelcome and even dangerous encumbrance. The model is based on the use of the pilum without a throwing strap.

Over the centuries of its existence the Roman army used a variety of cavalry support units. The early legions were supported by 300 horse formed into a unit called the Ala. In the latter years of the Republic Caesar, for example, employed thousands of allied cavalry. At times, during the empire the role of the cavalry at times diminished to a few hundred support units. This page is not an attempt to describe these cavalry units in detail but is only intended to give a general view of the cavalry units and their sizes relative to the army as a whole. The basic cavalry soldier was almost always armed with a shield and stabbing spear, supplemented by a sword. The Romans were never noted for using mounted archers, for example. The appearance of the cavalry soldier would surely have changed over time.


The Roman roads were constructed for military purposes. It is obvious that, whenever possible, the army moved along the roads. Therefore the width of the paved roads determined the width of the Roman column. Most descriptions ignore this factor. Judson, for example, describes the army marching on a 40 foot front. There were no Roman roads that were 40' wide. However, most descriptions of the army on the march state that the soldiers marched 6 abreast. The standard spacing is usually given at 3' for each file. Allowing 1 foot between the edge of the road and the lane in which the outside soldier marches requires a minimum road width of 18 feet. This 18' road width is drawn in red in the illustration. The top set of blue figures show a rank of 6 soldiers on 3' intervals and how they would fit into the road widths. The lower set of figures squeezes the 6 men into a width that would fit the Via Appia when it was repaved, 14 1/2 feet. This formation does not seem viable to me in that the actual width of each man, including his gear is 2'6" and the allowed width for each file is 2'7". There is only 3" between the outside man's foot and the edge of the road. It does not seem feasible that six men could march with their gear in that tight a formation. The conclusion is that the standard description of 6 abreast only works on certain road surfaces. On many roads, some of which were as narrow as 5 1/2 feet, the number of files would have to be reduced and the length of the column extended accordingly. During the era of conquest the Roman armies ventured into new territory that did not have the fine Roman road system. I have no information about the conditions of those roads but can only assume that they were inferior to the Roman roads, probably more like tracks in many cases. The tidy arrangement of ranks and files and marching units would hardly be appropriate when visualizing the army moving under those circumstances.

Horses, Mules, Oxen, Carts and Wagons

The baggage train took up most of the marching column. A few introductory words about how the Romans transported their baggage is in order. The Romans had no large draft horses, nor had the horse harness been invented. The yoke system that was developed for oxen was poorly suited for horses. Horses were generally used only to pull light two wheeled carts. Heavy wagons were pulled by oxen. Ancient wagons were designed to be pulled by two animals. Horses and mules can travel at about the same speed as a man, 3 to 4 miles per hours. Oxen travel only about 1 mile per hour. The preferred method of transport was by pack mule. Several different mule packs are represented in the illustrations for the march. The pack for the mule carrying the contubernium's tent and equipment is loosely modelled on a photo of a modern re-enactment group. The other loads are imaginary. However it seems useful to make them look different to underscore the fact that there would have been quite different loads for different parts of the baggage train. Including different packs in the illustrations encourages thinking about the great variety of material that the army needed to take with it. 

The Army

Roman armies came in many variations over the centuries. For most of the republic the 4 legion army was standard, during the late republic armies became much larger. Under the empire many of the legions became less mobile, serving more as static border guards than as mobile armies. In the late empire the entire army structure changed with much greater weight being placed on the cavalry units. The types and numbers of light infantry (skirmishers) changed over the centuries. The early legions used velites from the legion itself as skirmishers, later armies employed auxiliary skirmishers. The cavalry also changed. The early legions had a small contingent of Roman and allied cavalry, later the cavalry consisted almost exclusively of auxiliaries. Under empire there were periods where there was not much cavalry associated with the armies and then, later, when cavalry took on a much greater role. 

The Contubernium

Throughout the centuries it seems that the basic unit of the Roman army was the contubernium, the tent mates. There is ambiguity and disagreement among the sources about the number of men that made up a contubernium. Some consider the contubernium to have consisted of 8 soldiers, others 10, with 2 on watch. What does seem clear is that only 8 men could sleep in the standard 10' by 10' tent. The discrepancies are in whether the tent-unit included 10 men with two always on watch or was just 8 men. The elements of the contubernium are: 10 soldiers, 1 10' by 10' tent, 1 mule and 1 servant. The mule is cared for and led by the servant (calo). The tents poles and stakes are estimated to weigh 40 pounds. The maximum load for a pack animal was estimated at 200 pounds but one was assigned to each tent to carry the extra food, baskets for excavating trenches, a handmill to grind grain, and a variety of other tools and equipment. The pack includes a folded tent, the tent poles, two large baskets on either side filled with tools and cooking utensils, and a sack of grain.

The Centurion

Each centurion is assigned his own tent, a mule and a servant. The centurion's tent was 10' by 10'. Each officer is assigned one mule to carry the tent and their personal gear. The mules packs are different from that of the contubernium since there are no entrenching tools used.

Optio: The optio may or may not have had a tent. 


All authors agree that 8 men could sleep in the contubernium tent and modern reenactors confirm this. On this basis, 1 tent is assigned to each 8 servants since none of them would have been on watch. In most cases I allotted 1 tent to each 8 servants, but where there were 9 or 10 in a unit, rather than add a tent for one or two people, I crowded the extra servants into the one tent. The pack mule for the servants is again slightly different from that for the contubernium. It lacks the baskets and entrenching tools but has some additional cooking utensils. The tent represented is the same size as that for the contubernium.

The Century

The size of the century varied from time to time in the history of the legion. There were noticeable differences between actual and theoretical legion strength as well. For the purpose of the models I have considered the century to be 80 men: 8 contubernia, 1 centurion, a signifer and an aeneator (either a cornicen or a tubicen). 

The Maniple and Cohort

Two centuries made one maniple and three maniples made up one cohort.  The two centuries of the maniple have 10' between them, as do their respective baggage trains. There is 20' between each maniple. The borders of the three maniples are colored, top to bottom, blue, red and green to help distinguish them.

The Legion

Ten cohorts make up one legion. The ten cohorts take 3,726 feet in the column of march, the baggage train for the legion is nearly as long, 3,580 feet.

The Decuria, Turma and Ala

The number of Roman cavalry assigned to the legions varied over time but an early standard seems to have been 330 to the legion organized into a unit called the ala (wing). It was comprised of ten turmae. Each turma consisted of three decuriae of 10 soldiers and an officer called a decurio. 

Pack train: Each decuria has one tent for its ten soldiers and one for its officer. One additional tent is added for the servants, making a pack train of 7 animals for each turma. The turmae which did march in a battle-ready condition would need pack mules for their personal gear. The ten turmae would not have marched in this formation since they used to scout in advance, guard the flanks and read and guard officers and important baggage. I show the distribution of the Roman cavalry forces later in conjunction with the auxiliary cavalry.


Each legion had 6 tribunes who served as officers to the legate. They are shown in the illustration on the left with their baggage train. Each tribune has a tent, a personal pack mule and one extra horse that is led by a servant. Three tents are required for their servants.


Each legion was under the command of a legatus. The legate is assigned a large tent that requires two mules to carry, 4 personal pack mules, and extra horse. There is one tent for the servants.


The signiferi are always mentioned but there is seldom a specific allowance made for them when the army is described. For example, the usual descriptions do not mention tent locations in the camp or baggage requirements. The first rank has four signiferi in it. They represent the signiferi of the legion proper are left to right, an aquilifer, imaginifer, draconarius and an old style signifer carrying a taurus, bull, standard. Following them are the 60 signiferi for the centuries. Then come four vexillarii for the four centuries of antisignani and finally three mounted signiferi: a vexillarius for the legion itself (shown mounted because he accompanies the legate), a vexillarius for the Roman ala, and a draconarius for the ala. 


Aeneator is the generic name for the soldiers who carried the signaling horns. Just like the signiferi, the aeneatores did not march together but were disbursed throughout the legion. The usual numbers for a legion, are: one cornicen is assigned to the first century and one tubicen to the second; 30 each per legion plus 3 of each to the cavalry units, 1 tubicen to the legate in command of the legion and 1 tubicen to the first tribune. One bucinator to each cohort, 1 to the cavalry and 1 to the legate in command.


In the earliest legions the skirmishers were the velites attached to the third line. In later legions they consisted of auxiliary units of specialists, mostly slingers and archers. The trains are long for several reasons. The skirmishers were used as advance scouts during the march. Because of the nature of their weapons (lead shot or stones, bows and arrows ) they would require some additional supply. Four mules, one for each 20 skirmishers, have been assigned for this purpose. If these soldiers were on active duty as light fast infantry they would not have carried their own gear, as did the legionaries. Since the load for one man is usually set at 40 pounds, one mule for each 5 men has been assigned for personal gear. this makes for a considerable pack train, a total of 33 mules per century to carry the tents, gear and servants tents.


In addition the legion would have scribes to keep its records and accounts. I arbitrarily assigned 16 to the legion: 1 for each of the 10 cohorts, 1 for the ala, 1 for the fabri, 1 to keep the supply accounts, 1 as an overall paymaster and role keeper, 1 to the tribunes and1 to the legate. The scribes were probably slaves. The pack train is very large because the scribes kept the records of the legion and would have had bulky sets of scrolls, blanks scrolls, writing supplies and writing desks. They may even have had charge of pay chests. Because the scribes would have needed a place to work out of the weather it seems reasonable to assign each a tent of his own to protect his records and be his office for the conduct of his official duties in camp. 

The Engineers (Fabri)

The army always had some body of professional engineers with it for siege work, bridges and roads, fortifications and other construction projects. Since an army might engage in several construction projects simultaneously, all requiring close supervision by the fabri. 


At some times in the long history of the legion it also carried a variety of artillery pieces with it. a ballista, a two armed stone thrower. Onager, a single armed stone thrower. a small arrow shooting scorpio. The catapultae were the arrow shooting pieces, the ballistae were the stone throwers. Catapults could be relatively small and carried on a single mule. Judson estimates the weights at 84 pounds for the small ones and up to 600 pounds for the large ones. Even the small ones would require two men to operate them. By Vegetius' time it seems that the legion was equipped with 50 to 60 small catapultae, probably scorpiones, and 10 ballistae. In the earlier legions the ballista was preferred to the onager since it was more efficient, under the late empire the onager became the predominate siege weapon. Imperial legions had an artillery piece, the carroballista, that appears to have been mounted on a special cart. 


The army must have had significant quantity of extra supplies such as tentage leather, clothing, weapons, cordage. 

Defensive stakes: The stakes found at some locations are interpreted as additional defensive works. They are, typically, about 5' long, tapering from a maximum width of 4" at the center to a point on either end, with a recessed "handle" in the middle. Each soldier may have carried one stake or they could have been carried by mules. If the stakes were tied together to create an additional defense on top of the walls of the camp then 6852 feet of wall would need to be covered. The stakes are about 4" in diameter, 3 stakes to the foot would require 14,506 stakes to defend the entire circuit of walls. Since there are about 19,440 legionary soldiers in the typical 4 legion army there would be enough stakes for the purpose if each soldier carried one. A stake of dried wood some 5' long, tapering to both ends and only 4" wide at the widest would not weigh more than several pounds. One mule could conceivably carry 100 of them, 145 mules for the entire supply or 36 mules per legion. The burden for one mule would be a bundle of 10 by 10 stakes, or 40 by 40 inches, perhaps not too heavy but possibly too unwieldy for a single mule load. 

Medical Staff

Wounded soldiers may have been carried from the battlefield on their shields, but those not able to walk would have had to have some alternate form of transportation, either to get from camp to camp or to be returned to some more secure base camp. In either case, it would seem likely that the legion would have some type of ambulance carts available for this purpose. For ambulances I have allowed 1 light two wheeled horse-drawn cart per cohort, driven by one of the assistants. The remaining 10 assistants care for the mule train. Trajan's column shows soldiers being cared for by what look like other soldiers. However, it seems that most doctors in the Roman world were slaves or freedmen. Therefore, if the legions took actual doctors with them then it seems likely that they would have been slaves or freedmen, not soldiers. The soldiers themselves may have assisted in caring for the wounded, analogous to field medics.

Hospital tents: It seems reasonable that the very ill or seriously wounded would be cared for at some kind of central aid centre, a field hospital of sorts. If there were hospital tents they could have been relatively small, on the same order as an officer's tent which could easily be carried on the ambulance carts. On the other hand, it is likely that the very ill or gravely wounded would not continue to accompany the army but would be left behind in some kind of secure base camp, reducing the need for a hospital. 


At least by the late republic the commander employed professional body guards made up of paid mercenaries. It seems that the number of bodyguards was not standard but depended on the general. For this model I have used a strength of one cohort, 480 soldiers. The bodyguards are foot soldiers but travel mounted so that they can keep up with the general. Since they are foot soldiers, not cavalry, they are organized into a cohort. The cohort strength, 480 men, is equal to just under 15 turmae, about 1 1/2 alae of cavalry. The small units at the top represent the commanding officer of the bodyguards, his signiferi, aeneatores and pack train. Following the commander is one century of 80 men. Immediately behind the 3 aeneatores of the commander is the officer rank (detail below) followed by 13 ranks of soldiers. Since the bodyguards would travel in a battle-ready mode, their personal gear would have to be carried by pack mules. I have followed the standard I used above, 1 mule for each five soldiers. There are 9 mules with tents for the 8 contubernia of soldiers and their officer. Then there are 18 mules carrying the personal gear of the century, and finally 4 tents for the servants. The bodyguards escorted the commanding general as a unit. Their march and baggage train formations are shown below. The guards are in red, the baggage train is blue.


The evocati were retired soldiers who came back to serve at the specific request of the commander. They sometimes formed part of the bodyguard, otherwise served as special units at the service of the general. They are described as foot soldiers who each had a horse. I have not found any indication of the numbers of evocati; it seems probable that there was no "typical" number but that it would depend on circumstances and generals. I used a total strength of one cohort, and used the same formation and baggage model as for the bodyguards.

Noble Youth

(contubernales, comites praetorii)

It was the custom for young men of noble families to accompany the Legions as a part of their education process. It is assumed that each youth had a personal servant and tent. The servants could have shared a single tent. For 8 youth there would be one additional tent for servants.


Under the republic the army would be commanded by either a consul or a praetor. A consul would be accompanied by 12 lictors, a praetor by 6. For a consular army of 2 legions and 2 allied units the 12 lictors would require 2 tents, three mules for their personal gear which they could not carry themselves, and one tent for the servants. 

The General

(Consul, Praetor, promagistrate or imperial general)

The commanding officer of the army certainly had more elaborate accommodations than the other officers. If the general's tent was the size Connolly indicates it would take 4 mules just to carry the poles and tent leather. In addition the general is allotted 20 personal pack animals and 1 extra riding horse led by servants, and 4 tents for servants. The pack train did not move with the general. The entourage that would have moved with the general on the march is shown below. The general, consul or praetor, is described as moving with a large entourage accompanying him. The commanding officer of the army may have been a dictator, consul, praetor, promagistrate or imperial general. For this illustration I have depicted a consul with his 12 lictors. A dictator would have had 24 lictors, a praetor only 6. Imperial generals would not have had lictors. In fact it seems that they were used in many capacities and may not have occupied this particularly place in the order of march.


The army, at least under the republic, had a quaestor assigned to it to keep the accounts. The quaestor is assigned a large tent the same size as the general's; a 4-mule load. He has 2 mounted personal servants. The quaestor would have required a number of clerks, but no specific numbers are given. The pack train consists of 4 mules for tents, 10 mules for the quaestor's personal gear, 6 mules for the tents of the clerks (one each as an office), 7 mules with official documents and equipment (two for the chief clerk, one each for the others), 4 mules for the servants tents, and an extra riding horse for the quaestor.

Auxiliary Cavalry

The number of auxiliary cavalry varied greatly from army to army. It seems that Caesar may have employed the greatest numbers, 4,000 to 5,000. Other armies may have employed almost none. For the purpose of the model a moderate force of 8 alae, 2,640 cavalry is used. There were also 4 Roman alae (one per legion) for a total cavalry force of 3,960 men. Distribution of the cavalry and other mounted units during the march: The mounted soldiers in this army are: 4 alae of Roman cavalry, 8 alae of auxiliary cavalry, 1 cohort of bodyguards and 1 cohort of evocati. The sources I have used indicate that various parts of the column were protected by cavalry but do not give unit identifications or numbers. For the purposes of guarding the column I am considering the mounted foot soldiers, the bodyguards and evocati, as cavalry. The mounted units are distributed: Roman cavalry: 4 alae: 1to the vanguard, 1 as guard for the officers, 2 to the army equipment and supply baggage; auxiliary cavalry: 8 alae: 1 to the scouts, 1 to the vanguard, 2 to the rearguard, 2 to each flank; evocati: to guard the officers baggage train; bodyguards: to guard the general. This arrangement puts three alae in front of the column (one with the scouts, two with the vanguard), two on each flank and two with the rearguard. It distributes the remaining 3 alae and the two mounted cohorts at intervals along the column of march.

Iron Supply, Forge and Smithing

The army in any extended campaign would have to provide for the repair and replacement of its weapons. The wood parts could be manufactured from materials found through forage or manufactured on site but iron would have to be either captured from enemy stockpiles, recovered from broken Roman weapons or recovered enemy weapons, or drawn from a supply taken with the Army. It does seem likely that the army would take some supply of bronze and iron with it and not rely solely on recovered or found supplies of these essential materials. Each soldier must have carried a minimum of 10 to 15 pounds of metal in armour and weapons. In addition there would be tools, parts of harnesses, artillery fittings, arrow points, sling shot (often made of lead). An army of roughly 20,000 soldiers would carry, then, something like 200,000 to 300,000 pounds of metal weapons and tools. If as little as 1% of the total weight of metal were taken as a reserve that would be 2,000 to 3,000 pounds. With an average mule-load of 200 pounds it would take a train of 10 to 15 mules. The repair of weapons would require a small forge and smithing tools. I have not been able to find any information on portable Roman forges. Given the difficulty of wheeled transport, the ideal forge would be carried by mules. It may be possible that a simple portable forge could consist of a dozen or so fire bricks and a bellows. The loose bricks and bellows could be carried on a single mule, the smithing tools on another. A small 200 pound anvil could consist of two or more parts that, when disassembled, could be loaded another mule. Thus a very small, primitive, but workable blacksmith setup could be transported on as few as 3 mules. If the forge consisted of these small parts -- bricks, small anvils, tools -- it would look much like any other mule load. Since each legion has a supply train of 288 mules, over a thousand for the whole army, it seems adequate to assume that some of these supply train mules were used to transport the necessary quantities of metal and materials for portable forges.

Spoils of War

The spoils of war figured large in the army's activities. Some campaigns netted enormous quantities of precious metals, objects of art and slaves. The quantity of spoils actually accompanying an army in the field would be highly variable: none at the beginning of a campaign, perhaps a great deal at certain times. Some of the booty would have been transported to secure forts in rear areas. At some times, certainly, the acquired spoils would have had to travel with the army itself. It is likely that an important part of the spoils of war would be the transport necessary to move it -- wagons, horses, mules. 

Time to Fortify the New Camp

Most estimate that it took 3 hours to complete the fortifications around the camp, Judson estimated 3 to 4 hours. The first legionary soldiers to arrive with the vanguard do not begin fortification work but, rather, set up a protective screen to defend the site and the new arrivals. Work on fortifications do not begin until the first of the regular legionary forces arrive.

Rate of March

The Roman militari gradu, regular march cadence, was 100 paces per minute, the quick march cadence was 120 paces per minute. The Roman foot was (0.9708 English foot). The pace was 2.5 Roman feet, (29.124"). At that rate the army would move 14,562 feet per hour, 2.76 miles per hour. It would take each unit a little over 3 1/2 hours to complete the ten miles between camps. Because of the length of the column, it would take a little over 8 hours from the time the first units left camp until the last of the rearguard arrived at the new camp.

Peaceful and Hostile Marches

The Romans are said to have enforced the camp building procedure every night, whether in peaceful or hostile environments. The main difference seems to be that the fortifications were more elaborate when there was a potential threat. Otherwise, the description of the march as given here would be similar whether the army was moving through Italy on its way to the provinces or through Gaul and Spain during a campaign.

All ancient people rose early. In summer months the army would be up and moving by 6. This would allow them to complete the day's march at about 3 in the afternoon, leaving a good portion of the day for the other tasks that would still need to be done -- caring for the pack animals, repairing equipment, cooking meals, scouting the area, foraging for food, firewood, restocking water supplies, drill and relaxation.

The Order of March

Scouts - A scouting unit of cavalry and skirmishers was stationed 800 yards in front of the main body. 1/2 of the skirmishers and 1/8 of the auxiliary cavalry were assigned to scouting. That is, 4 centuries of archers, 4 of slingers and 1 ala of auxiliary cavalry. The pack animals for these units are positioned with the overall army supply train.

Vanguard - The vanguard consisted of one legion and cavalry. The legion was chosen by lot daily. The vanguard would have been some distance in front of the army, about 800 yards as a likely distance.

Survey - The survey group was comprised of one man from each contubernium.

Pioneer - The composition of the pioneer corps included one cohort and 10 engineers. 

Officer Corps - Chief among the officers is the quaestor. Then there are the officers of the 4 legions: the legati in charge of each legion and the 6 tribunes assigned to each legion. Each legatus is accompanied by one of each of the types of aeneatores. Also included is the commander of the allied cavalry and the quaestor. The quaestor is accompanied by 4 clerks. The officers are grouped by legion.

Baggage Train - First come the evocati as a guard unit. Then the baggage of the commanding general and the officers. This is followed by the baggage of the legionaries, then that of the staff for the legions, the Roman alae and the archers and slingers. In roughly the middle of the train there is another mounted guard of 2 Roman alae. They are followed by the baggage for the army; its artillery, supplies and food. And finally there is the baggage of the evocati, bodyguards and auxiliary cavalry. In the model above the baggage train has been grouped by similar types. That is, all of the artillery, food and supplies for each of the four legions has been grouped together. The Romans also organized their order of march legion by legion, with the baggage of each legion accompanying the legionaries. Were a legion to march on its own, as they often did, this would approximate the formation, although the legion would probably have advance and rearguards that are not shown.

Rearguard - Connolly describes the rearguard as light and heavy infantry plus a considerable number of auxiliary cavalry. The alae are at the end since they are the more mobile and could more easily fight a rear guard action and then catch up to the main body.

Flank Guards - Some cavalry units would have been used as flankers to protect against surprise attacks. 

The Entire Column - This column extends almost 15 miles. The column would be considerably extended if the roads being used did not allow the army to march 6 abreast. It is significant to note the extent of the baggage train, nearly 8 miles from front to back. This vulnerable part of the column would have been difficult to defend. If there were an attack on the middle of the baggage train it would be approximately 4 miles to the rearguard and to nearest legion front, but nearly 6 miles to the foremost legion. Signaling horns could raise the alarm from one end of the column to the other almost instantaneously. The mounted rearguard could cover the distance in about 10 or 15 minutes but would take between one and two hours for the legions to arrive on the scene.

Men and Animals - Contubernium, 10 men are assigned to one tent, eight sleeping, two on watch. They have one pack animal to carry the tent and other supplies and a servant to handle the animal. To simplify the model all pack animals are considered to be mules, animals ridden (by the cavalry and officers) are horses and oxen are not included.

Cavalry - The normal ala formation was 40' wide so that it could move in formation on the 40' road. On a 20' road the Cavalry would march by turma, 8 ranks of 4 files. 

Servants - One servant is assigned to each mule. Since servants do not keep watch, there is one tent for each 8 servants.

Legion staff

Legatus - One to command each legion under the general.

Quaestor - One to the army.

Contubernales, comites praetorii - Young nobles accompanying the general as aides. He does not specify a number.

Apparitores - Lictors, scribes and servants. No numbers given.

Body-guard - Again, no numbers are given. They are described as sometimes drawn from the army, sometimes drawn from the Evocati, sometimes hired mercenaries.

Evocati - Retired legionaries serving as a special corps at the invitation of the general, their former commander in some cases. They were formed into regular centuries but served a variety of functions including orderlies, scouts and protection of the general.

Fabri - Engineers, led by the Praefectus Fabrum. Some may have been leginaries, others would have been specialists. No numbers are given.

Antisignani - Although disputed by some of his authorities, Judson says that each maniple may have had one contubernium, 10 men, who were antisignani. They would operate in front of the legion as light troops or skirmishers. They marched without heavy baggage. Caesar, he says, "regarded the body as a school for centurions."

Mules - Load. The maximum load for a mule is given as 200 lbs. Number. There are between 520 and 640 per legion, depending on the actual strength of the legion. Spacing. In the march he allows 10' for each rank and 5' for each file.

Equipment and Supplies

Artillery - There are two types, the catapultae (bolt throwers) and ballistae (rock throwers). The catapulta weighs between 84 pounds (smallest) and 600 pounds (largest). The ballista weighs about 200 pounds. Each legion had 55 carroballistae (smaller ballistae) and 10 onagri. Since no mention is made of wheeled transport, all artillery items are considered to be carried on mules. Ballistae. The smallest ballista had arms 2' long, powered by skeins 4" in diameter. The largest had arms 4' long and was powered by skeins 6' to 8" in diameter. The ballista could throw a 6 to 8 lb. stone 450 to 500 yards. The onager was known all along but only came into general use quite late when the more complicated but more efficient ballistae went out of use. He estimates the weight of an onager as 2 to 6 tons. It probably had a range 400 to 500 yards. Onagri were not used in the field but were only for sieges Number. By the time of Vegetius 10 onagri were assigned to a legion, or 1 per cohort, one carroballista per century. Probably the artillery was not actually distributed to those units, it is more likely that the artillery was centrally concentrated and that the description reflects a formula to determine the number each legion would have. Staff. Although there is no direct evidence he believes there would have been an artillery commander, a principalis, in overall charge. Similarly, each carroballista would need a junior commander, an aimer, 1 or 2 men to turn the winch, and 1 or 2 animal handlers who could also help re-supply ammunition. He assigns a total 10 to the carroballista. Vegetius suggested that a team of 11 men were required for each. The onager, especially the larger ones, would have required more men. The total artillerymen per legion would be about 650, plus artificers. They were sometimes called ballistarii. They may not have been in special units, but may have been drawn from the regular legionary force. However, after 300 AD they were assembled into their own units. 

Tents - The standard soldier's tent is 10 feet square and weighs 40 pounds. The centurion's tent was 10' by 20' wide and was probably carried on a small two wheeled cart pulled by two mules and driven by a servant. The cart would also have carried extra gear and supplies for the century and been a place to store personal gear in the case of battle. Tribune and officer. The tribune's tent was taller, on a box-like structure of poles. General. The general's tent may have been some 200 square feet. Caesar, even carried a mosaic floor in sections.

Carts - Use. Although not used extensively, he believes the Roman army would have used small mobile two wheeled carts pulled by two animals (mules, horses or oxen) for at least some of the baggage. Number. Each legion would have had 60 carts for its artillery, 60 for the centurions, and another 30 for "sundry" needs such as ambulances, engineering supplies. Pace. Caesar's light duty two wheeled carts as capable of 4 mph.

Food - The daily grain requirements were 3 lbs. per day for each man. Each man carried 10 day's rations (30 pounds) with another 2 days rations being carried on the mules. 125 mules were assigned per legio for ration reserve function but 1,250 for the army as a whole. "Ration reserve" may mean that they carry rations for two days and then act as a reserve for forage or loot or other needs. The mule-borne rations would be consumed first to free those mules to carry found foraging and or booty.

Booty - The army may acquire considerable booty as it conquered land and cities. He does not attempt to cite any specific number of animals or servants or hostages associated with booty.

The March

The legions marched at 3 miles per hour. Carts were capable of 4 miles per hour.

Order of march:

Scouts. An advance force was sent in front of the army to scout for enemy ambushes. This force was composed of about 1,000 cavalry plus some light infantry of archers and slingers. They operated about 800 to 900 yards (roughly 1/2 mile) in front of the vanguard.

Flank. 1,000 cavalry on each flank as protection from ambush.

Rear Guard. 1,000 of the auxiliary cavalry with the rear guard.

Order of march::

  1. Scouts: Light infantry and cavalry as scouts
  2. Vanguard: one legion and cavalry
  3. Camp surveyors: 10 men from each century (1 per contubernium), with kit and instruments to lay out campsite.
  4. Pioneer corps to clear or bridge obstacles
  5. Generals personal baggage and that of his staff officers, with a strong mounted escort
  6. The general and his bodyguard, drawn from the auxiliary cavalry and infantry
  7. The artillery borne on mules
  8. Legates, Tribunes, auxiliary prefects with escort of picked troops
  9. The legions, each led by an aquilifer and the other standard bearers, either led or followed by trumpets and horns.
  10. Each legion was followed by its baggage and servants, extra servants marching behind the baggage
  11. Auxiliary cohorts in formations like the legion
  12. Rearguard of light and heavy infantry and a large body of auxiliary cavalry
  13. Camp followers, merchants, slave dealers

Transport - The preferred method of land transport was by mule pack. The use of wagons was limited because without the horse collar neither horses, mules nor donkeys could pull heavy loads and oxen were slow. Human labor moved lighter weights. The maximum human load that could be carried more than a short distance, 40 or 50 yards, was 50 to 60 pounds. Anything larger required pack animals. The very heavy loads were drawn by oxen in wagons.

Mules - They were normally from a female horse and male donkey, were preferred over horses for several reasons: they were less temperamental, easier to train, their skin is tougher and less easily damaged, can tolerate extremes of heat and cold better, requires less water, needs less sleep (4 to 5 hours per night), its hooves are harder and is more sure-footed. The mule walks at just over 3 miles per hour but can cover up to 50 miles a day over level ground and lightly loaded. Because of these advantages, pack mules were widely used throughout the world until this century. Evidence seems to indicate that ancient mules were roughly the size of modern mules: between 52 and 60 inches at the withers (13 to 15 hands), the largest as high as 64 inches, weighing between 6000 and 900 pounds, able to carry 30% of their weight (25% on hilly ground). The load could be between 200 pounds for a smaller mule and as high as 270 pounds for a large one. An important restriction was that the weight had to be evenly divided on either side of the pannier. If a single large weight, a stone, for example, were carried then the mule could only bear about half the weight.

Donkeys - They were also used, though it seems that mules were preferred. They are smaller than mules, between 36 and 60 inches at the withers, carrying proportionately smaller loads. A small donkey could carry about 120 pounds, a large one the same as a mule.

Horses - Ancient horses were probably about the same size as the mules. Large draft horses were not known in ancient times. Four well-bred horses might have been able to pull 2 to 3 tons at about 4 to 5 miles per hour. But the ancients actually used them to pull light loads, such as a chariot and its driver, maybe 440 pounds at a relatively fast pace. Horse drawn fast vehicles could average about 7 mph over the course of a day.

Oxen - Oxen can pull 1.5 times their body weight but can travel only 1 miles per hour, less if there are obstacles in their way. However they do have advantages in feeding since they can consume 1.5 times 3% instead of 2% of their body weight. They can survive on lower quality food since they can eat more of it. One ancient formula says that they should be fed 15 lbs. of hay and 15 to 20 pounds of mash per day.

Carts and Wagons - Two wheeled Carts and four wheeled wagons were both used. Oxen were used for the wagons and the heavy carts. Horses were used for light fast 2-wheeled carts, usually personal transport. A difficulty with the two heeled heavy carts was that the load had to be precisely balanced over the wheels or it would exert pressure on the pole either down on the yoke or up on the girth strap. There may have been a standard gauge for wagons of 112 to 114 cm. This is found in grooves worn by wagon wheels in various places. Heavy wagons were usually drawn by oxen, horses were used only for light fast transport. Both carts and wagons were designed to be drawn by two animals. The method of attaching them to the vehicles was yoke and pole, suitable for oxen but not for horses since the yoke choked the horse if too heavy a load were pulled. The horse collar was not invented until centuries later.


One can only try to imagine the confusion inherent in an ancient battle. 
It would have been difficult for anyone to see much of what was happening. A small army, the equivalent of just 4 legions plus cavalry, would have a front of nearly a mile. A larger army, typical of the late Republic and early Empire, might be made up 8 to 12 Legions and have a front of several miles. Moreover, battlefields were selected because they were flat and allowed the armies room to manoeuvre. But, being flat, they offered no vantage points higher than the back of a horse. Because most warfare took place in the summer months, dust would have been a frequent problem. Distance and dust would have made it nearly impossible to tell what was happening at other parts of the battle. The noise would have been horrific. Initially there would be the sounds of trumpets and thousands of men yelling on both sides. During the battle there would be added the sounds of shields and swords smashing together, orders shouted, men calling encouragement to their comrades or shouting threats to the enemy, the thunder of horses hooves, the cries of wounded and dying men. It is possible that the regular infantryman could hardly hear his own officers.

The nice neat unit formations we see on paper simply disappear, replaced by a melee of men. The battle line is not straight, or well defined, or stationery. Rather there is a moving seething mass of men sometimes hotly engaged, sometimes falling back. At a quick glance it would be difficult to tell which side was having the better of it. At times it was, apparently, even difficult to tell which side was which. Any model of Roman fighting has to depart from the tidy paper diagram and reflect the inherent confusion of the real place. Elaborate manoeuvres and complicated tactics would probably not have even been possible. It would have been important for the individual soldier to stay in close contact with his comrades on all sides of him, to feel and sense their presence and support even when he was tightly focused on the enemy in front of him. Any sort of coordination between units must have been difficult and, at times, impossible. Large scale coordination would have been extraordinarily difficult, but not impossible as we will note later.

The ability of the commander to control his army during battle was probably not great. As noted above, it would have been difficult to see or hear much of what was happening during the battle.
1,700 yards - masses of troops can be recognized
1,300 yards - infantry can be distinguished from cavalry.
1,000 yards - individuals can be seen.
700 yards - heads, crossbelts etc. can be distinguished
500 yards - uniforms recognized, reflections from weapons
250 yards - officers recognizable, uniforms clear

Visibility would be obstructed by men and horses in the line of sight. The ability to distinguish friend from foe would be more difficult when seeing units from the sides or back. Everything would be in motion. And even a little dust in the air would significantly reduce the amount of detail and color that could be seen at a distance..

Roman commanders seem to have favoured a position on their right flank, traditionally the strongest and most aggressive wing of the army. Even Pompey at Pharsalus, where the major action was expected on the open left flank, took up his position on the right. From this side a general could hardly have seen what was going on some 1,700 yards away on the left flank. For information he would have had to depend on messengers or other indicators. Pompey is said to have deduced the outcome of the cavalry fighting by observing the dust clouds raised. If the riders could travel at the "rapid" pace of 8 mph it would take about 13 minutes to ride the length of a 3,000 yard battlefield. By the time the general could receive the report, issue new orders, and send the rider back there would be a delay of nearly 1/2 hour. Some battles may have lasted half-a-day, but others were over in a matter of a few hours. In those cases a delay in communications of 1/2 hour would be significant. For this reason the Romans used horns to signal orders over long distances. The general would still be dependent on dispatch riders to give him information about the status of events at distant points but he would have been able to issue simple types of commands via horn signals. Keeping noise factors in mind, there would have had to have been a relay system to ensure communications with the furthest units.

Battlefield Obstructions

Intricate manoeuvres would be hampered by an assortment of obstructions on the battlefield. Most depictions ignore this. True, most battles were fought on relatively flat smooth ground. Even a flat field would have many minor obstructions. A relatively small boulder or bush could seriously disrupt the tidy ranks and files that appear on paper. In addition to natural obstacles there would be a considerable amount of debris from fighting. Along a front of 100 men there would be a between 200 and 400 pila that had been thrown - many now stuck in the ground, some (say a dozen) lodged in a discarded shield or in the corpse of a casualty. Along that same 100 man front a casualty rate of just 3% would leave 6 bodies (3 from each side) lying on the field. Near each of the 6 bodies would be a sword or spear, a shield and possibly a helmet lying on the ground as well. There could be another 12 wounded who may have been removed from the field but whose equipment might be lying around. A front of 100 would take up roughly 300 feet. Along that front there would be one pilum every 9 inches, a pilum-scutum tangle every 25', a body every 50' and equipment of the dead and wounded every three feet. This detritus of battle could be scattered for some distance on either side of the current line of fighting, but even so, it would remain as an obstacle to troop movement. Just about every century on the line would find itself moving over and around these obstacles. At a minimum this would disrupt the ranks and files. It could be much more serious when soldiers tripped and fell, as they would almost inevitably have done. Manoeuvring by any unit would have to be over and around these obstacles. It is not impossible to maneuver, but it is not as simple, orderly and precise as it appears on paper.

In the second half of the 2nd century BC the Romans made the momentous decision to abolish the legionary cavalry and employ foreign horsemen, raised in the areas of operation and led by their own chief or Roman commanders. Under the republic command had been exercised by native princes, but under the empire commanders were soon drawn exclusively from Roman equestrian prefects.: During the late republic most cavalry were Celtic and used a spatha, 60 to 70 cm in length, and a flat oval shield. The auxiliary infantry varied from light-armed troops such as the slingers shown on Trajan's column, who wore no armour at all and, if the artist is to be believed, no shoes either, to fully armed troops whose armour was identical to that of the legionaries but of inferior quality: the only difference was the use of the flat shield rather than the scutum. Unarmoured cavalry was comprised of one hand spear-bearers, pike-bearers and lancers, other skirmishers (mounted-bowmen or javelin-throwers). The spear-bearers are those who approach the enemy ranks and fight them off with spears or charge and drive them back with pikes like the Alans and Sarmatians, the skirmishers are those who discharge weapons from a distance, like the Armenians and those of the Parthians who do not carry pikes. ...The name of skirmishers is given to those who do not come to close quarters but discharge their weapons from a distance; and of these some use throwing-spears and others bows. ... But others first discharge their weapons and then join battle with the enemy, either retaining one of their spears or using a sword (spatha).

It is hard to wheel about with square formations --  are well arranged in as much as those so drawn up are in ranks and files and it is organized for easy charging and withdrawing; and only with this formation do the officers fall in a single body upon the enemy. The best are those that have the double measurement in the length rather than the breadth; for example, if there are ten men drawn up along the front and five deep. For such formations are oblong as regards number, but square in actual shape. For the length of the horse from head to tail fills out the square since the length of the horse is three times a man's width at the shoulders and as when they draw up nine in line along the front, they make the formation three deep. For this too should be borne in mind, that the cavalry drawn up in depth do not afford the same assistance as to infantry in depth, for they do not push on those in front of them, since one horse cannot push against another in the way that infantry push on with their shoulders and flanks, nor when they are contiguous with those drawn up in front do they constitute a single massed weight for the whole body of troops; on the contrary, if they mass and press against each other, they rather cause the horses to panic. An oblong formation in which ... the front is greater than the depth ... is better in contests. ... A single line along the front with no depth is convenient for unsuspected raids ... but for contests it is very disadvantageous. Horsemen gallop in circular patterns throwing their javelins at targets. In the practice formations the turma appears to string itself out as individuals following one behind the other through the loops of the pattern.

The spatha blade was 34 inches. Josephus mentions three or more light javelins being carried in a quiver. At one gallop stride a 16 hand horse can cover at least 16 feet. A ploy for confusing the enemy as to the size of the army was for the cavalry were to be lined up extremely close together so that the whole unit looked much smaller than it really was. This left no room to manoeuvre. Each horse was allotted a space 3 ft wide by 8 ft long. I have measured this out with a horse. Katchina at 14.3 hands hits easily into this space lengthwise, and when he is in fit condition into the width also. Nizzolan, of oriental blood being pure Arabian, and a much leaner type but slightly taller than Katchina at 15 hands fits, with a little room to spare. There is just sufficient room widthwise for the troopers knees. 

The speed of a foot javelineer prior to the throw was very important. The speed of the horse definitely lent power to the cast. As it leaves the hand the speed of a modern man's javelin weighing 800 grams is between 27 and 30 meters a second. A speed of 33 meters per second is exceptional. Loss of force occurs in flight. As it reaches its highest point, before starting on its downward flight, it is traveling at approximately 9.81 meters per second.

Light-armoured cavalry ... were considered to be the most versatile and the most useful of all the styles of mounted troops. They were usually positioned on the flanks of an army, from where they could try to harass , and hopefully, encircle the enemy's wings. ...This type of cavalry was particularly well suited to skirmishing, making constant sallies against the enemy in order to exhaust the infantry and force them to be continually on their guard. Unlike the heavy-armoured cavalry, whose role it was to charge an army directly, the light-armoured mounted troops were specifically equipped to wear down an enemy through persistence.

Cavalry is only an effective arm when it is offensively employed, since once it is forced to become defensive, and is confined in a restricted area, it loses its main advantages of mobility and speed. ... The charge must be decided promptly, and executed vigorously; always met and carried out at speed ... No distance can be laid down at which to charge, it depends on so many different circumstances. When the ground is favourable and your horses in good condition, you can strike into a gallop sooner; but the burst, the charge itself, must always be reserved till within 50 yards, for in that distance no horse, however bad, can be left behind, nor is there time to scatter, and they fall upon the enemy with the greatest effect.

Well disciplined, determined infantry, could rarely be defeated by this manoeuvre (charging) ... One of the main reasons for this is that horses, whenever possible, will avoid a direct collision with an obstacle, and thus when they are confronted by a wall of unyielding spear points they will instinctively try to wheel away from them. Only if the infantry has lost its nerve, and the courage needed to hold fast has gone, will the charge be able to break the line and scatter the men in disarray. If, however, he does persist, and charge home on our heavy infantry centre, then the second and third ranks of the legions will close up on the front, until they are actually touching, so as physically to support them under the shock of impact; thus the attacking horsemen will be confronted with an unbroken and immovable hedge of spear points at the level of a horse's chest. Spearmen in the fourth rank will thrust at them, and those of the fifth and flowing will throw their spears overhand. By this means we cannot fail to repulse the enemy and force him to retire in disorder with heavy loses.

When the cavalry engaged in close-quarter fighting with infantry, their height advantage would become a very effective means of slashing at the heads and backs of their opponents, although, of course, they themselves would be vulnerable to leg wounds. If, however, they were engaged with enemy cavalry, the wounds incurred would be of a different nature, and the battle itself must have been absolute mayhem, with horses rearing and throwing their riders on to the ground, where they would stand little chance of escaping the hooves of the other mounts. The report of a cavalry officer who fought at the Battle of Balaclava, although comparative, paints a graphic picture of the sheer horror and confusion that was presumably present at all such fights: 'I can't say I saw the man who hit me, we were all in a crowd cutting and hacking at each other, and I did not know till some time after that I was touched when my wrist got stiff, then I found the cut through my coat, it was only bruised for a few days ... The wounds our long swords made were terrible, heads nearly cut off apparently at a stroke, and a great number must have died who got away. Our corporal who was killed was nearly cut to pieces, his left arm nearly severed in four places ... All of the Russians seem to cut at the let wrist, so many men lost fingers and got their hands cut.' 

Among the aspects of Roman warfare the use of elephants has to be one of the hardest to understand. There is ample evidence that they were used both against the Romans and also by them. There is some evidence that they were effective in some instances, but there are more examples in which trained soldiers fought against elephants quite effectively. The best testimony for their [elephants] usefulness in combat still remains, however, the fact that even the great commanders always used them again and again, especially Hannibal and also Caesar. . . . If we consider the entire experience of the military history of antiquity, we may say that the usefulness and the actual use of elephants for battle may under any circumstances not be rated too highly. Against peoples who were still not at all familiar with them and against cavalry and sharpshooters they had some successes, which were, however, as in the case of the battles against Pyrrhus, for example, very greatly exaggerated by the losers in order to find an excuse for their defeat. Troops who are familiar with them and do not fear them, who know how to avoid them and how to attack them properly, are able to deal with them . . . by skillful use of their weapons. . . . The elephant is not at all invulnerable but even has a rather sensitive hide, and even if spears and arrows do not kill him outright, they still penetrate so deeply that they remain imbedded in his body, and the pain makes the animals uncontrollable and causes them to shy away. It is reported often enough that they then penetrate into the ranks of their own troops, throw them into confusion, and bring about defeats. . . As the ultimate means of dealing with such cases, the mahouts ... each had a sharp steel wedge which they drove with a hammer into the animal's neck in order to kill him and render him harmless.


Wages (per month)
Messenger 36
Legionary Soldier  80
Praetorian (guard in Rome) 240
Optio 120
Centurion 1200


The Roman Era