Many times, taking the status quo for granted is the normal mode we all operate in. In this context, when growing up in the 1980’s, if one aspired to study “things military”, you would simply accept the organizational structures of various militaries without question. Studying old – even ancient – military organizations was seen as a good thing for historical research, but really didn’t have much utility in the modern day…
…Or did it?
On New Year’s Day 2023, I had one of those head-slap moments, when I realized something profound: In some four thousand years of recorded military history, only nine organizational units have made it down through history, some of which still exist to this day. Nine. There have been other unit organizations, certainly, but none of them have ever taken hold for any length of time, and none of them are ever seriously considered for resurrection. This is not a merely academic idea, either – trillion-dollar military budgets are largely based on supporting these unit formations (in theory, at least).
Today, we’re going to explore a basic outline of those nine unit types.
The Tribal War Band
The Tribal War Band is the oldest continuously used formation in recorded history. It is an amorphous collection of extended family and clan warriors, hastily assembled to either make a raid, or defend against one, after which it would disperse until needed again. The War Band grew out of familial hunting parties that took advantage of human numbers, communications and cooperative effort to hunt down either game animals, or predators encroaching on the family/tribe’s hunting/foraging grounds. In many parts of the world today, the tribal war band continues, as underdeveloped areas and peoples see no reason for a more formalized organization.
Combat for the old war band was similar to the kind of melee combat popular in modern television shows and movies, being essentially a street or bar brawl, albeit with swords and spears, instead of sharpened bicycle chains and switchblade knives.
The tribal war band, in the modern day, remains dangerous primarily because it is almost impossible to gather meaningful intelligence on them, and thus it is nearly impossible to create plans to counter them by remote study and planning techniques. The only solutions in the “military tool box” are to use massive, overwhelming force and numbers to occupy and saturate an area, or to send in tiny parties on the ground, to locate the tribe[s] in question, and find out more information about them…which is usually vastly more effective – and practical – than simply running the proverbial steamroller over the area.
The Phalanx
The Phalanx was the first regularized tactical unit on record. While we know of armies before the time of Classical Greece – those of Sumer, or Egypt and the Hittites, specifically, as well as armies in China and India – those armies did not leave a record of their formal organizations.
In contrast, the ancient Greeks, as first described by the poet Homer, deployed their armies of citizen-spearmen – the Hoplites – in a rigid, square or rectangular formation, of anywhere from 100 to 500 men, and occasionally more, in files of 16 to 32 troops. These troops were armed with a sword and shield, but their main weapon was the “sarissa”, a type of spear or pike that could be up to twenty feet in length. In combat, the phalanx would try to use its weight and mass to basically “shove” the opposing phalanx off the battlefield. In a contest where the sides were more or less evenly matched, this came down to individual physical strength and stamina, and a willingness to hold out until the enemy got tired, and decided to try and run for it…and, as in most battles before about 1900AD, that would be where the real casualties would happen.
The phalanx has disappeared, only being resurrected by pre-gunpowder forces that were unable to organize or train for anything more complex, because the formation had severe and fundamental flaws: it was hard to keep it in formation; it was slow and clumsy to move in anything but a straight line; and it was helpless against lightly armed forces, such as archers, slingers or peltasts (a type of skirmisher that threw javelins).
As soon as the phalanx met an infantry formation that was more flexible, it was completely torn apart.
The Contubernium/Section
The next unit is the second-oldest unit overall, and the first of four units still in use to this day, well over two thousand years after its inception: the Contubernium.
The Contubernium (derived from a Latin term meaning, “tenting together”) was the basic eight-man unit of the Roman Army. It consisted of eight legionaries who lived, trained and fought – and occasionally died – together. Unlike their modern equivalent, the Section, there was little volatility in the Contubernium, as the legionaries within would frequently remain together for up to a decade or more, barring deaths or promotions. The contubernium was the basic building block for the next level up, that being the Century.
Today, the contubernium still exists as the “Section”. The modern Section of eight troops is used in many armies for the same purpose as its ancestor, as the infantry’s basic fighting unit in combat.
The Century/Company
The Century was a unit of 80-100 troops (the number varied over time). Their leaders, the Centurions were long-serving, professional officers, and had to be literate, have prior military experience in the ranks (at least in theory, although this was mostly true for most of the era), had to have “connections” (expressed in ‘letters of recommendation’) and had to be able to demonstrate proficiency with all the common weapons of the soldier. The centurions were simultaneously soldiers, officers, disciplinarians, combat commanders, administrators, and occasionally, even jurists or spies.
The modern Company, in contrast, is about one-half to twice the size of the Roman Century. However, that was an evolution, over about three hundred years, because the infantry Company, from before the American War of Independence, was roughly 50-80 men at full strength, until about the time of World War 1, with the advent of more complex weapons and the organizations to support them. However, the organization of the “fighting company” has remained stable at 100-200 troops. There have been attempts at explaining this, but the one theory that has taken hold is that 150 troops is the rough “sweet spot”, where one person can directly lead about 150 people in combat with only a minimal staff.
In the Mess, we call that “learning through trial & error”.
The Cohort/Battalion
The next level up from the Century/Company is the Cohort/Battalion. The Cohort was a subset of a Legion (q.v.), which had a total of ten Cohorts. The Cohort, like its descendant, was a collection of centuries. Unlike its descendant, however, the Cohort was generally fixed in size, at about 600 legionaries. The modern battalion, in contrast, can be anything from 300 to 1,200 troops in size, depending on its specific job and organization. (As an aside, some translations of John 18:3 note that it was a “Roman cohort” that arrived to arrest Jesus at Gethsemane.)
This level of command is typically regarded as both the first “operationally capable” unit that can operate on its own, as it includes its own internal (or, “organic”) support elements, such as a medical staff that offers more than First Aid +, communications, supply, maintenance and a number of other dedicated support elements, is considered to be the basic tactical unit in combat. In Roman times, specialist officers within the Cohort and Legion were assigned drafts of troops for non-fighting tasks such as building roads and entrenchments, or manning artillery pieces.
The Battalion, like its ancestor, forms the bedrock for larger units.
The Legion/Brigade
Rounding out the “units of history” is the legendary Roman Legion. Composed of ten Cohorts, plus additional troops (mostly cavalry and scouts) and support staff, a Roman Legion at full strength numbered anywhere from five thousand to seven thousand troops in size. The twenty-eight Legions of Octavian Augustus – a force estimated at c.300,000 troops overall – formed the core of a Roman military machine that would maintain the security of the Empire for nearly five centuries.
In the modern day, the basic structure of the Legion continues as the “Brigade”, which is at the core of most modern armies. While the modern-day brigade is a miniature army – effectively mirroring the Battalion albeit much larger in size – this was not always the case, as it evolved from an ad hoc grouping of Regiments (q.v.). With the end of the Cold War, however, most nations ‘downsized’ their militaries, leaving Divisions (q.v.) as mostly administrative commands for their component “maneuver brigades”. With the return of large-scale (if rather desultory) mechanized warfare with the 2022 Russian invasion of Ukraine, many nations are reevaluating their policies of leaving brigades to operate independently, outside the “support umbrella” provided by the Division.
In one of those quirks of history, the modern Brigade has approximately the same “bayonet strength” of troops as a Roman Legion, although it maintains larger support units.
De Re Militari
How is it that the preceding four organizations carried over to the modern day, over a span of some two thousand years? The answer lies in a book, De Re Militari (English translation), written sometime in the early 5th Century AD by a late-Roman author, Publius Flavius Vegetius Renatus. In it, Vegetius reviewed the organization, training and discipline of the old legionary system, attempting to convince the Emperor of the time to return to those methods. While those exhortations apparently had little effect on the Western Empire, copies of the work circulated throughout the misnamed “Dark Ages”, until it received its first printed edition in 1473AD.
Kings and commanders throughout Western Europe tried to emulate various aspects of Vegetius’ work, but social, political and technological limitations hampered anything more than the most basic of his ideas. With the rise of larger, better-organized states in the 15th Century, however, Vegetius’ ideas became viable, and many states – especially after the near-total adoption of firearms as the main personal combat weapon in the various armies – latched onto the book as a template for their new, much larger forces.
The Tercio
The Tercio (from the Spanish term for “a third”) is somewhat unique in this list, as it only really lasted for about one hundred and fifty years, at most, but had an impact out of all proportion to its size and organization. This was because it was the first unit in modern times to show the potential of what infantry was actually capable of, in an arena where the mounted knight had been viewed as the dominant power.
As originally organized, the tercio deployed was split into three more or less equal types of infantry: pikemen, swordsmen and crossbowmen. Rapidly, however, the arquebus replaced the crossbow, and the swordsmen began to dwindle in number, replaced by troops carrying halberds. Eventually, as the arquebus first became cheaper, then evolved into the musket, the swordsmen disappeared entirely. The result was the first real “combined arms” formation since the Roman Legions, a unit of 400-3,000 troops what could operate independently of outside support.
The tercio revolutionized warfare, and lead directly to the next ‘unit of history’, the Regiment.
The Regiment…and the Bayonet
The Regiment evolved out of the Tercio, as the technology of military firearms advanced. As the arquebus evolved into the musket, it was realized that coordinated firepower was the infantry’s final, real answer to cavalry dominance. However, while the Tercio did have advantages, the use of pikes was increasingly seen as a waste of troops: while the pikes did well in protecting the infantry from cavalry attacks, commanders wanted to somehow combine the pike and the musket into a single weapon.
The answer came in the form of the bayonet.
In the late 17th Century, around 1671AD or so, French General Jean Martinet standardized the first practical bayonet (so named for its purported place of invention, the French city of Bayonne), the so-called “plug bayonet”. The plug bayonet was exactly that: it was essentially a type of dagger, fitted with a small, round hilt made of wood, that could be quickly inserted into the muzzle of a musket, turning it into a type of spear, which could be used to fend off cavalry that got too close, a common occurrence, given the limitations of the muskets of the time.
Obviously, though, this type of weapon was not ideal, as it could only be used while the musket was empty. The plug bayonet quickly evolved into the “socket bayonet”, which was fitted over the outside of the muzzle and was offset to one side, allowing the soldier to load and fire his musket while the bayonet was fixed.
It was at this point – in c.1700 – where the Tercio, as such, finally disappeared and was replaced by the Regiment.
This is not a useless digression – by eliminating the pike, military units (at least in Europe) became all-firearm formations, capable of both maximizing firepower, while simultaneously being able to counter direct cavalry shock attack.
The bayoneted musket directly allowed the creation of the Regiment. Nominally a unit of 500-1,000 troops, the regiment was usually organized into ten equal companies, ideally of 50-100 troops each, with a regimental command staff to handle administration, medicine and logistics. The troops could – as their Roman predecessors had been – be assigned to various specialist tasks under the supervision of officers skilled in fortification and road building, although gunpowder artillery was left to specially trained soldiers, given the dangers involved.
The Regiment, in this format, remained the dominant maneuver unit until after World War 1. Although the term was occasionally used interchangeably with the Battalion – even today – the Regiment remains the bridge between the Battalion and the Brigade. In its most basic form, the modern regiment is composed of two to three battalions, with perhaps a battalion’s worth of support units. This organization is the source of some confusion, as it appear to resemble a brigade…however, the main difference between the two units is in the number of support personnel.
Three hundred years on, the Regiment – while evolved in size and organization – is still going strong, and shows no sign of disappearing anytime soon.
The Division
While there has always been a delineation of larger military units into “divisions”, the modern Division (capitalized intentionally) originated during the Napoleonic Wars, as Napoleon reorganized the French Army into Divisions and Corps’.
In the modern day, a division typically consists of three brigades, of three “fighting” regiments/battalions each, with their associated support elements, and a collection of other support units under the direct control of the division headquarters. Numbers-wise, the division can range anywhere from 6,000-25,000 troops, depending on its composition, mission and national military doctrines.
As referenced above, while the Division faded into an administrative grouping in most nations following the end of the Cold War, the current (as of January of 2023AD) war between Russia and Ukraine is causing a serious reconsideration of reviving the Division as an operational combat command among nations fearful of being drawn, once again, into an all-out, conventional (hopefully) slugging match.
Conclusion
Why is it important to know these things? Well…that really depends on one’s view of their place in the world: How much do you trust your government to properly inform you of what is happening with your nation’s military? When you see or hear a news story about “military unit X”, what does that mean? Is it a minor issue, or a major one? The popular media rarely, if ever, bother to try and explain it to you, and when they do, they usually get it wrong.
To paraphrase historian Niall Ferguson, in his 2008 series “The Ascent of Money”, not knowing this stuff can seriously affect your life.
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