Battlefield Formations

A Realistic Parade Formation

The previous pages have depicted the legion formations in schematic terms, following the pattern set by the illustrations one finds in books. But these are idealistic formations based on perfect arrangement of the ranks and files, full strength units, and usually represent what we might call parade ground formations.

What is missing is a clear discussion of the actual formation as it might have existed in battle.

The illustration left below shows the 80 man century as it is often depicted. The 80 men are arranged in 8 ranks and 10 files. In front of them are the signifer, the centurion, the optio and the cornicen

The illustration on the right below shows the same century with some significant differences that are explained below.

The main problem with the standard diagram is that it supposes that the unit is at full strength. This was probably a rare exception. When we do know actual troop strengths it is clear that legions were always understrength, sometimes by very large percentages.

The illustration on the right shows four categories of missing soldiers.

Orange: There are four officers sown at the front of the company: a signifier, a centurion, an optio, and a cornicen. All but the centurion were drawn from the ranks of the 80 man unit itself. The three orange circles indicate that three of the 80 men are officers, not included in the ranks and files.

Green: The legions had excellent medical care. At least some of the doctors were non-combatant personnel, but it seems that some of what we would call medics were ordinary soldiers trained for the job. For a combat unit of 80 men two medics do not seem excessive. They are present on the battlefield but behind, not in, the rank and file formation.

Magenta: At least by the late republic the legions had artillery as a regular part of their equipment. In theory, at least, each century had a scorpio and each cohort had a ballista. Two men are detached from the century to man its scorpio. One man is detached from each of the six centuries of the cohort to man its ballista.

Blue: Military units are always understrength. Recruiting quotas may not be filled. There are inevitable losses during basic training. Illness on the campaign has been a leading cause of death until modern times. And, of course, there are those killed and wounded in fighting. The number of men a unit would be understrength could be anything up to half of its strength. This particular century is shown as missing 9 soldiers.

A Battlefield Formation

The illustration on the right shows the same century in battle formation, which is different from the parade-ground formation shown above. The centurion takes his place in the front rank of the right file, the place of honor. We are fairly certain of this placement for the centurion. As he takes his place in the first rank, one more soldier is added to the last rank which now has 4 instead of the 3 in the parade formation.

The cornicen, the optio and the signifer have moved to the back of the formation.

The decision to place the standards behind the formation is probably controversial. Almost every representation will show the standards at the front of the century.

Delbruck (Vol 1: p 278) discussed the probable placement of the standards and signaling horns at some length. He concludes that the standards were behind the maniples in the pre-cohort legion formation but in the second rank in the cohort formation. The rationale for the move is not well explained. It is with some degree of trepidation that one argues with Delbruck, however the placement of the standards at the front of the formation simply defies understanding. The standards were the symbols of the unit, highly valued by the soldiers, and highly prized trophies by the enemy. The soldiers holding the standards needed both hands and had only a small shield that was virtually useless. In other words, they were defenseless. It is nearly impossible to imagine placing these men in the first or second ranks of the unit.

There is some slight evidence in Caesar's Gallic War commentary [2:25] to support this point of view. In a battle with the Nervii he records that all of the centurions in the fourth cohort of the 12th legion had been killed, and one standard bearer killed and the standard lost. There would have been 6 centurions and 6 standards in the cohort. In this cohort, then, 6 centurions who were excellent soldiers and well able to defend themselves were killed. If the standard beares who were unable to defend themselves had been next to them then it would seem likely more than one of them would also have been killed. Especially considering that they carried the most sought after trophy of war.

The optio can fulfill two important functions from the back of the formation. First he can keep good order among the troops, ensure that no one tries to slip away from the formation, and move men around to fill in gaps or weak spots as they occur. He is also in a good position to receive and relay commands from the tribune or legate.

Behind the optio are the two medical orderlies, distinguishable by their silver armor. These are men from the century itself, trained as orderlies. They have 8 servants to carry the two litters.

To one side there are two servants with a mule carrying water. Meeting the need for water would be critical. Most ancient battles were fought in the summer months, under the Mediterranean sun, by men wearing metal armor. Lack of water could easily lead to heat stroke, incapacitating the soldier. The mule could carry about 250 pounds, roughly 30 gallons (113 liters) of water. Counting soldiers, officers and servants, the century depicted has 79 men. That would give them each about 3 pints of water per mule load. During a long battle the water would have to be replenished.

The soldiers detached to handle the artillery are not depicted since they would be located elsewhere on the battlefield.

The Cohort Battlefield Formation

The 6 centuries of the cohort are shown below in a relatively realistic manner. That is, if we had a bird-eye view of a Roman formation it would have more closely resembled this illustration than the standard ones shown in most books. The centuries are shown with different manpower strengths. The most artificial elements in its appearance are the alignment of the cohorts into straight line and of the centuries into straight ranks and files. However, as a result of endless drills, it is likely that they aligned themselves for battle in formations as straight and true as possible, perhaps even with the assistance of surveyors laying out the battlefield positions in advance.

Just behind the litter bearers there is a single horseman for each century. This is a courier for getting information back to the commanders. For this role it is proposed that some of the evocati be used. The evocati were retired soldiers who volunteered to accompany a commander for a specific campaign. Here and there the evocati are mentioned in a battle -- Caesar seems to indicate that they led a charge even --but evidence about just how the evocati were used in battle is minimal. Because of their status and age it seems unlikely that they were used as front-line fighters. But they certainly could have fulfilled many other necessary functions, such as acting as couriers during the battle. Using them as couriers is speculative. However, whether or not they were evocati, there probably were couriers and they were probably mounted.

The other option for mounted couriers would be to use some of the Roman cavalry for this purpose. Although the number of Roman cavalry differed over time, a typical number was 120 per legion. It appears that most of the cavalry fighting was done by allied cavalry, not the Roman cavalry. So, if they were not fighting then they could well have been used for scouting and courier work. At 120 per legion there could be 1 assigned to each of the 60 centuries, some to the legion commander, some to the wing general and some to the commanding general.

The placement of the two servants with the water and the two medical orderlies with their litter is also speculative, but reasonable. We know that the Romans had good medical care for the wounded soldiers. For that to be at all effective some orderlies would have to be near the action to evacuate the wounded during the battle whenever that was possible. As for the water, men fighting in the summer heat would require lots of water if the battle extended for any length of time at all.

In several instances it appears that the Romans may have engaged in lengthy missile exchanges instead of close hand to hand sword fighting. In at least one case, Caesar notes it, the Romans were set upon so fast that they could not throw their pila and had to discard them so they could use their swords. Soldiers may have carried two pila; they are reported to have done so. Since only one can be used once the fighting starts, the second pila, if it was carried to the battlefield and not left behind in the camp, would have to have been set aside somewhere behind the unit. And, finally, debris would accumulate underfoot. Before and during the fighting missiles of various sorts would be hurled into the formation, some falling to the ground. Wounded soldiers would drop swords, helmets and shields. Pieces of armor or clothing could come loose. For a formation trying to fight in formation, having anything underfoot would be dangerous. If the century were in a static position (neither charging nor retreating) then it would be in the best interests of safety for soldiers in the middle and rear ranks to get rid of whatever is on the ground. Some missiles might be thrown back at the enemy but broken ones and other debris would need to be moved to the rear to get them of the way. All of these situations probably require the presence of servants or soldiers in the rear who either supplied additional pila or were responsible to help clear clutter. In this model there is no allowance for these individuals and/or their possible pack animals (one can imagine a mule loaded with pila). But the possibility of their presence should be noted, at least.

There would almost certainly be any number of other individuals running around behind the front line. But, since we do not know about their roles or identities, I elected not to try to include any additional figures in the drawing.

At the bottom of the illustration the first rank of the second echelon is shown to give a sense of the space between the lines.

The Legion Battlefield Formation

The final illustration in this series is the legion formation. this shows the 10 cohorts in a triplex acies formation. The second line is close to the first so that it can more rapidly support it. The third line is further back and acts more as an echelon force, available for re-deployment as the need arises.


The groups of 7 horsemen behind each cohort represent the tribunes who may have had command of the cohorts. The use of tribunes as cohort commanders may not have begun until the empire, so if they should be omitted if the army were thought of as republican. There is also the possibility that the tribunes were more administrators than battle commanders. However, as Delbruck notes, once the tactical unit of the army became the cohort it would seem to be a military necessity to have a single commander, and one that could be reached more easily and reliably than the centurion.

"In time, perhaps under Augustus or possibly not until Hadrian, the tribunes also became permanent commanders of the cohorts, a situation that actually would have been required by the military principle as early as Marius' time. The legions continuously had six tribunes, whereas they had ten cohorts, and we are told expressly by Vegetius that the cohorts were commanded partly by tribunes, partly by praepostiti . . . the balance . . . was provided for by holding four positions as cohort commanders for promoted centurions." [Delbruck:Vol. 2, p 167]


"Each legion had a legate as permanent commander, perhaps as early as Caesar's time." [Delbruck:Vol. 2, p 167]

The legate's group appears behind the third echelon of the legion.

At the head of the group of horsemen is the legate, followed by 4 mounted arneatores (mounted, so that they can keep up with the commander as he moves around), and 10 zzzevocati who can be used as couriers relaying commands or carrying information to the commanding general.

It should be noted that much of this is speculation. What we do know is that the legates were in command of the legions and that commanders had some staff with them. Beyond that, it is a matter of making reasonable guesses. We do not know what staff they had with them or if they commanded from the middle, sides or back of the formations.

The 6 standing soldiers are 4 aeneatores, the legion's aquilifer and the vexillarius. There is no evidence to support this placement, it is based on the idea that the most important symbols of the legion would not be in the front line, would not be between lines where they would interfere with battle maneuvers, and so therefore would be behind the lines with the legion commander.

The General

Roman generals commanded from all positions but it seems that the most favored location was from a position just behind the right side of the front line. Caesar often took a position on the right side of his army but also moved around from legion to legion during battles. In the illustration above the general is shown just behind the first line of cohorts. There would certainly be more room for maneuver if the general and his entourage were behind the second line instead of the first.

It is challenging to attempt to visualize just what a general's command post might have looked like. Who would be with the general?

We should probably imagine messengers coming and going constantly, keeping the general informed of developments, and relaying commands. There would probably also be aeneatores to signal his instructions with their trumpets. The general may well have had a personal flag, a vexillum. We know that many top commanders, certainly those after Caesar, had bodyguards. It seems likely that the general would have at least some protection around him. And all of these individuals would need to be mounted.

The illustration below tries to flesh out these suppositions. It shows the general in front. Behind him his vexillarius is flanked by 8 aeneatores, enough to sound a signal loud enough to be heard at some distance. On either side are some of the 40 mounted bodyguards.

The Army Battlefield Formation

The next illustration shows the four legions making up the heavy infantry of the Generic Army.

This is the same diagram as the legion formation shown above, just converted to blocks instead of individual figures. the types of units are color coded. The general and his entourage are represented by the solid orange block. The legates commanding each legion by the light green blocks, the tribunes (who may not have commanded cohorts until the first century BCE) are purple blocks. Behind each cohort are the small blocks representing their support men.

On either side of the legions there are wings of 12 alae and two centuries of light infantry. They are illustrated below.

This image is at a slightly larger scale than the 4 legion diagram just above. In this larger view, the support blocks can be distinguished. The red is the medic unit, the blue represents the water supply. For the cavalry three water mules are provided for each 333 man alae because of the needs of the horses. Behind each ala is a purple block representing the ala commander, and behind the wing is the light green box for the wing commander. In this model the army is shown with two equal wings of cavalry on either flank. In many battles the cavalry was used predominately on one side or the other, depending on terrain and the enemy dispositions.

The entire army is illustrated below.

This shows the entire army with all of its support elements as it would appear based on this particular model.

The full scale drawing makes it clearer how difficult it would have been for the commander to exercise any real control over his army once combat actually began. His knowledge of events on his left flank would be minimal and what little information he did obtain would be outdated by the time a courier could get to him. Any orders sent back would arrive many minutes later still. This underlines the importance of the unit commanders who must have had to exercise considerable independent authority, as, indeed, the evidence bears out.

On either flank, just between the infantry and the cavalry are two centuries of light infantry.

The only new element added in this image are the 6 columns of additional water supply well behind the army. Long battles or exceptionally hot weather would probably require replenishment of the supply sent forward with each century.


Command, Control and Chaos

This depiction of the battlefield should raise some questions about just how a general could exercise any sort of command and control from the position shown. One needs to imagine 3 more legions like this spread out to the left. The challenge of exercising leadership over such a battlefield is difficult to imagine. The general could see only a small piece of the actual battle and would know of other developments only by way of messengers.

We should also not imagine a general of the caliber of Caesar being stationary during the battle. His command post would be in constant motion. There are numerous examples of him riding from one end of a battle to the other, encouraging his men, calling for changes in positions and reinforcements, even taking up a shield and entering the fray himself. Whenever he moved, somehow his location would have to be communicated to his subordinate commanders so that they would know where to send messengers with reports.

One can imagine the general and his entourage on the move. Couriers trailing him around the battlefield, trying to find him and then to catch up with his fast moving command center to deliver their messages. At various places the second and even third line units begin to fill in the space between the lines, making travel and communications between commanders even more difficult. Dust clouds raised by the thousands of men and horses would obscure anything that is at a distance. The noise of combat would all but drown out even the loudest horns.

Truly, the chaos of battle cannot be pictured and can hardly even be imagined

Purpose and Value of the Models

The purpose of these models is not to suggest that any Roman army ever looked like this.

The purpose is, rather, to try to correct the error that almost all depictions of the Roman army make; that is, they omit everyone but the rank and file soldiers from the illustrations. They do that, of course, because so little is known about them. The question is, is it better to simply omit them or to include them even if the numbers types and placements can only be speculative.

The usefulness including them in these models is to remind the reader that there were command units on the battlefield. That is known. That they had to have some number of men associated with them, and that they had to be located somewhere on the battlefield. Even if the guesses made in these illustrations are incorrect, they still give a basis from which one can make changes and adjustments. In my opinion, it is an improvement of omitting them altogether.

The scenario worked out on these pages has shown one way that the century could have moved from its tents to the battlefield. It is important to emphasize that the model does not presume to be a definitive description of how the Romans actually moved their army. We do not have enough information to know the details. At best, the models are reasonable guesses as to how it might have been done. But with considerable confidence we could say that the Romans almost certainly did not do it the way these models show. With their thousand years of experience, they surely found more effective ways of organizing their war activities than we can imagine from out distant vantage.

It is easy to be general and somewhat vague in written descriptions: "the optio stood behind the line." But when a visual model is constructed that ambiguity has to be resolved, the optio has to be drawn at an exact location, the word "behind" has to be given a specific meaning. This is both the benefit and the problem with models, for we simply do not know enough to accurately represent the Roman army. But, it is hoped that the attempt to do so can at least serve some useful purposes. Because they offer a visual clarity, they may help generate some insights into aspects of the army that are not otherwise obvious. The realization that the army may well have moved in columns-of-two's because of the space allocations inside the camp is an example. But even if that insight were incorrect, the process of thinking through just how the men did get from tent to battlefield is useful. And in all cases, the models should raise questions. All of that, I think, is good.

Above all, it is hoped that the models give a somewhat greater appreciation for the complexity of Roman warfare.

Links to the five parts of the Deployment section:
Deploying the Army: Planning
Deploying the Army: Exiting the Camp
Deploying the Army: Assembling the Units
Deploying the Army: Marching to the Battlefield
Deploying the Army: Forming in Battle Formation

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2003, Gary Brueggeman. All rights reserved world wide. No part of this work may be reproduced in part or whole, in any form or by any means, without permission from the author.