Supplemental material concerning the march
For modeling the Roman Army on the march I have used three main sources for the constituents of the army and the order of march:: Harry Pratt Judson, Caesar's Army; Peter Connolly, Greece and Rome at War; and John Peddie, The Roman War Machine. Supplemental information about mules as pack animals, horse-drawn carts and ox-drawn wagons comes from J. G. Landels, Engineering in the Ancient World and information about draft animals from several websites. The full references for the books are listed in the bibliograpy page. Summaries of some of the material from these sources follows.
Judson, writing in 1888, relies in part on even earlier authors such as Rüstow and Göler. Though more recent discoveries have improved our understanding of the Roman army, Judson wrote from a time that was closer to the non-technological world than we are today and therefore had experiences that were closer to those of the ancients. The armies of his day, for example, still relied on mules and horses and, within recent history, had drilled and fought in close order formations. In addition, he gives more intricate detail in some respects than modern authors. For these reasons I consider him a useful, but not definitive, source.
The key elements of Judson's model are summarized below.
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. He allows 10' for each rank and 5' for each file.
- Servants: One servant is assigned to each mule. Since servants do not keep watch, there is one tent for each 8 servants.
- Legatus: One to command each legion under the commander in chief.
- Quaestor: One to the army.
- Contubernales, comites praetorii: Young nobles accompanying the general as aides. Judson 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 legionaries, 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 Antesignani. 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
- Rations: He gives the daily food ration as 1.66 pounds. Soldier carry rations for up to 17 days and a total pack of up to 30 to 45 pounds, in addition to their arms and armor.
- Artillery: There are two types, the catapultae (bolt throwers) and ballistae (rock throwers). The catapult weighs between 84 pounds (smallest) and 600 pounds (largest). The ballista weighs about 200 pounds. The quantities are unknown until Vegetius wrote that 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.
- Tents: The standard soldier's tent is 10 feet square and weighs 40 pounds.
March spacing and pace
- Men. Judson allow 3' width to each file and 4' for each rank. His description is based on units of either 10 or 5 files, depending on the whether the road was 40' or 20' wide. road.
- Mules. He allows 5' for each rank and 10' for each file.
- Pace. He cites Vegetius' data for the militari gradu, 40,000 steps of 2.5 ft and quick step, 48,000 steps in 5 hours. 100 or 120 steps per minute. He references Uptons Tactics, a manual in use by the U. S. army in the 1800's which prescribed a step of 30 inches from heel to heel and a cadence of 100 and 120 steps; "exactly the Roman standard." Distance.
- Roads. He bases his descriptions on road widths of either 40' or 20'. He notes Caesar made his bridge over the Rhine 40' wide; evidence, he believes, of the standard marching width of the Roman column. In a 40' span he places 10 files, on a 20' road he places 5 files.
Order of march
The van (primum agmen) the main body (exercitus, omnes copiae, agmen legionum) and the rear-guard (agmen novissimum, agmen extremum). In the main body each legion may have been followed by its own baggage or all of the baggage could be gathered together. If the latter then the baggage came about 3/4 of the way back in the column with the remaining (claudunt agmen) bringing up the rear.
Extent of the legion on the march
With its baggage a legion would extend something 2,050 to 3,900 feet, depending on its actual strength.
One day's march
The average march, he says, would have been 14.6 to 19.5 English miles, depending on the amount of daylight. Again he cites the U. S. army standard of 15 to 20 miles with a rest every 10 minutes.
John Peddie wrote in 1994, some 106 years after Judson's book. He brings the benefit of modern reserarch to the description and gives a detailed analysis of the army that is useful in constructing models. He also bases his description on the army of Julius Caesar. A summary of his points are:
Men and animals
- Contubernium: 8 men with a servant and mule.
- Servants: He seems to imply that general animal handlers may have handled two mules each but he assigns one servant to each of the contubernium mules to care for the mule and serve the needs of the soldiers.
- Cavalry: He assigns the standard of 120 Roman cavalry per legion. For the entire army he has an auxiliary cavalry force of 4,000.
- Legion staff: He notes that the typical descriptions of legion makeup does not include many who would be in the headquarters staff such as ancillary troops, clerks, technician, specialists, reserve tentage, extra weapons, clothing cavalry equipment, field hospital, medical staff, veterinary staff, engineering stores and bridging equipment, artificers workshops. He cites some descriptions from Caesar to support an idea of 300 to 500 sick at any given time, leading to the belief that there would have had to have been some substantial hospital and ambulance presence in the army.
- Horses: He calculates 120 Roman cavalry to the legion, its normal complement.
- Mules: Number. To pull the cars there would have had to be 300. Add to that 125 to carry a reserve of rations and 850 for general duty -- 600 assigned to the contubernium, 250 for staff officers and other supporting services. He has a total number of baggage animals of 1130 for a legion and 8,750 for the six-legion army. That is 1,970 over those assigned to the legions, these would have supported the auxiliary troops, headquarters staff and cavalry. Spacing: He allows 15 feet per rank of mule or horse and 30' per cart. He has both mules and carts march 2 abreast. Pace. He describes Caesar's light duty two wheeled carts as capable of 4 mph. Load. he assignes 43,750 men to the legion, each with a food requirement of 3 pounds per day. He has 1,250 mules carrying a two day supply and notes that this is the equivalent of 112 wagons. 43,750 x 6 pounds / 1,250 mules = 210 pounds per mule; / 112 wagons = 2,343.75 pounds per wagon.
Total army makeup: He bases his description on a 6 legion army with the following troop and animal numbers:
- Legionary troops -- 30,000
- Ancillary troops -- 3,500
- Gallic cavalry wing -- 4,000
- Roman cavalry -- 720
- Servants -- 6250
- Horses -- 4,720 (not including those for officers)
- Mules -- hauling the reserve rations -- 1,250 (750 for the 6 legions and 500 for the rest of the army)
- Mules -- hauling the rest of the baggage and equipment -- 7,500.
- Tents: Standard. He describes the standard tent as 10 by 10. Centurion. 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 huge. He says that the marquee of the general's tent was some 200 square feet. Caesar, he notes, 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. He describes Caesar's light duty two wheeled carts as capable of 4 mph.
- Food: He estimates the daily grain requirements at 3 lbs per day for each man. He believes each man carried 10 day's rations (30 pounds) with another 2 days rations being carried on the mules. He assigns 125 mules per legio for this "ration reserve" function but has 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.
- Artillery: 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. He notes that Galwey estimated that the ballista could throw a 6 to 8 lb. stone 450 to 500 yards. Onager. 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 carrroballista 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. Similarily, 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 woudl 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 leginary force. However, after 300 AD they were assembled into their own units. Transport. He assignes one cart to each of the 60 carroballistae.
- Booty: He notes that 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.
March spacing and pace
- Men. He notes the annoyance of having the man behind step on the heels of the one in front and corresondingly allows each rank a full 6' (3' for the man and 3' between men). He does not specify the width of the file but has them 6 abreast.
- Mules and carts. He places carts 2 abreast and allows 30 feet for each rank. He does not specify the width of the file for mules but allows each rank 15'.
- Pace. The legions marched at 3 miles per hour. He notes in one place that the carts were capable of 4 miles per hour, in another place he estimates their actual speed as less than that of the legions.
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. He places 1,000 cavalry on each flank as protection from ambush.
- Rearguard. He places the final 1,000 of the auxiliary cavalry with the rearguard.
One day's march
He describes the army moving out of one camp and into next camp. The description is based on a march pace 3 mph, a distance of 10 miles between camps, and an overall length of the column of 22.5 miles. Times given are elapsed time from the time of departure.
- 00 Reconnaissance units (Scouts) depart
- 10m Vanguard departs followed by the command group and then the main body
- 3h20m Reconnaissance arrives at camp II
- 3h30m Vanguard arrives at camp II
- 3h30 Camp II layout begins
- 3h30m Head of baggage train departs camp I
- 4hrs Protective screen deployed as the first legion arrives at camp II
- 4hr30m Fortifications begin as the second legion arrives
- 6h30m Tail of main body arrives camp II
- 7h Head of the baggage train arrives at camp II; it moves at a slightly slower march rate than main body
- 7h30m Forticifcations complete
- 12h Tail of the baggage train arrives at camp II.
Order of march
- Scouts: Light infantry and cavalry as scouts
- Vanguard: one legion and cavalry
- Camp surveyors: 10 men from each century (1 per contubernium), with kit and instruments to lay out campsite.
- Pioneer corps to clear or bridge obstacles
- Generals personal baggage and that of his staff officers, with a strong mounted escort
- The general and his bodyguard, drawn from the auxiliary cavalry and infantry
- The artillery borne on mules
- Legates, tribunes, auxiliary prefects with escort of picked troops
- The legions, each led by an aquilifer and the other standardbearers, either led or followed by trumpets and horns.
- Each legion was followed by its baggage and servants, extra servants marching behind the baggage
- Auxiliary cohorts in formations like the legion
- Rearguard of light and heavy infantry and a large body of auxiliary cavalry
- Camp followers, merchants, slave dealers.
Landels discusses the role of horses, oxen and wheeled transport in the ancient world. Some salient points are as follows:
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 600 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.