Rome at War

The Etruscan Inheritance

When Rome appeared as a city-state in the Tiber valley some time in the middle of the eighth century bce, its first army differed little from those of other small communities in Latium. It is believed Rome’s first military organization was based on the tribal system, reflecting the three original Roman tribes (the Ramnes, the Tities, and the Luceres). Each tribe provided 1,000 infantry towards the army, made up of ten centuries consisting of 100 men. The tribal contingent was under the command of a tribunus or tribal officer. Together, these 3,000 men made up a legio or levy. This infantry force was supplemented by a small body of 300 equites or ‘knights’, aristocratic cavalry drawn equally from the three tribes.

Initially, the organization of the early Roman army was heavily influenced by their powerful neighbours to the north, the Etruscans. Etruscan civilization emerged in Etruria around 900 bce as a confederation of city-states. By 650 they had expanded in central Italy and become the dominant cultural and economic force in the region, trading widely with Greeks and Phoenicians on the peninsula. Under direct occupation by the Etruscans between c.625 and 509, Rome benefited greatly from this cultural exchange, with Roman villages transformed into a thriving city-state. As in ancient Sumeria and archaic Greece, each Etruscan city raised its own army. And although these cities were united in a league of usually twelve cities, they seldom operated together unless faced with an outside threat. Like the Greek poleis to the east, the Etruscan city-states spent most of their energy fighting each other.

Some time in the sixth century bce, the Etruscans adopted the Greek method of fighting and organized their militia-armies into phalanxes. After conquering the Roman city-state in the late sixth century bce, the newly created Etrusco-Roman army was composed of two parts: the Etruscans and their subjects the Romans and Latins. The Etruscans fought in the centre as heavy infantry hoplites, while the Romans and Latins fought in their native style with spears, axes and javelins on either wing. The army was divided into five classes depending on nationality. The largest contingent, or first class, was composed of Etruscan heavy infantry armed in Greek fashion with heavy thrusting spear and long sword, and protected by breastplate, helmet, greaves and a heavy round shield. The second class contained spearmen conscripted from subject peoples and armed in Italian fashion with spear, sword, helmet, greaves and the oval Italic shield or scutum. The third class was lightly armoured heavy infantry spearmen with scutum, while the fourth and fifth classes were light infantry javelineers and slingers.

The second of the Etruscan overlords in Rome, Servius Tullius, is credited in the middle of the sixth century bce with attempting to integrate the population by reorganizing the army according to wealth and not nationality. The Servian reforms reflected an old Indo-European custom where citizenship depended on property and the ability to maintain a panoply and serve in the militia. The reforms divided Etrusco-Roman society into seven groups. The wealthiest group formed the cavalry or equites, made up of Etruscan nobles and members of the Roman patrician class. The equites did not act in the capacity of heavy or light cavalry, but served as mounted infantry and reconnaissance.

The second wealthiest group acted as heavy infantry, fighting in the phalangeal formation and armed as before in the Greek manner. The third to sixth groups were armed in native Italian fashion identical to the pre-Servian period. The seventh class, or capite censi, were too poor to qualify for military service. Tactically, the Servian army fought as before, with heavy infantry in the centre phalanx, protected by lightly armoured heavy infantry on the wings and light infantry skirmishers in the front until the phalanx engaged. There is no mention of archers in the Servian reforms. Like the Greeks, the Romans seemed to disdain the bow and arrow as a weapon of war, preferring it for hunting.

The Early Roman Republican Army

In 509 bce the Romans overthrew Etruscan rule. Newly independent Rome replaced the Etruscan monarchy with a republic governed by a council of elders drawn from the wealthy patrician class. This council, or Senate, annually elected two consuls as chief magistrates of the Roman state. From 362 imperium, or the authority to command the Roman army, was entrusted to the consuls, or to their junior colleagues, the praetors. Though the election of co-rulers ensured a balance of political power, it had serious military drawbacks. The two consuls shared responsibilities for military operations, alternating command privileges every other day. Recognizing the inefficiency of this system, Roman law provided for the appointment of a dictator in times of national crisis for the duration of six months.

The early republican army was a citizen army. In fact, the original meaning for the word legion (derived from legere, Latin for ‘to gather together’) was a draft or levy of heavy infantry drawn from the property-owning citizen-farmers living around Rome. The army continued to adhere organizationally to the Servian reforms and consisted of three legions, each of 1,000 men, supplemented by light infantry provided by the poorer citizens and cavalry by the wealthy patrician class. Divided into ten centuries of 100 men, each legion was commanded by a tribune appointed from the patrician class, while each century was commanded by a centurion promoted or elected from the ranks of the legionaries. By the first century bce, legions were organized around a battlefield standard bearing an eagle, below which was inscribed the legion’s roman numeral and the letters ‘SPQR’ (Senatus Populusque Romanus), representing ‘both the sovereign Roman people and the advisory Senate which guided its actions’. And though the number of legions varied depending on the period, the importance of the legionary eagle as a visible sign of duty, honour and patriotism for generations of Roman soldiers remained constant for hundreds of years, even surviving Rome’s transition from republic to empire.

Nothing brought more dishonour to a Roman commander and his legion than losing their eagle in combat, and emperors would go to great lengths to get them back if lost. Caesar tells us that when his legionaries hesitated while landing in Britain in 55 bce, the aquilifer (eagle-standard-bearer) for the X Legion jumped into the waves and waded toward the half-naked, frenzied Britons. Fearing their eagle standard would be captured, the other legionaries flung themselves into the water and attacked the enemy. Rome’s first emperor, Octavian Augustus (r. 31 bce–14 ce), spent large sums of money recovering the eagle standards lost by the Roman general Marcus Licinius Crassus to the Parthians fifty years earlier at the battle of Carrhae in 53 bce. And when the elderly Augustus lost three legions and subsequently three eagles in the battle of Teutoburg in 9 ce, he is said to have wandered his palace muttering ‘Quintili Vare, legiones redde’ (‘Quintilius Varus, give me back my legions’).

During the first century of republican rule, the Roman army continued to utilize the phalanx-based tactical system. But the battle square proved less effective against opponents unaccustomed to the stylized hoplite warfare favoured by the Mediterranean classical civilizations. When, in 390 bce, 30,000 Gauls crossed the Apennines in search of plunder, the defending Roman legions were pushed against the Allia River. The Gauls, or Celts as they were also called, were an Indo-European people who inhabited an area of western Europe including modern Britain, the southern Netherlands, Switzerland and Germany west of the Rhine. Most of the Gauls were semi-nomadic (influenced by contacts with Greeks and Romans), organized into tribes and capable of fielding very large armies. The Roman phalanxes, outnumbered two to one and overwhelmed by the ferocity and physical size of the Celtic marauders, were defeated, unable to cope with the barbarians’ open formation and oblique attacks. The sack of the ‘Eternal City’ in 390 left a lasting impression on the psyche of Roman civilization. The surviving Romans who witnessed the violation of their city from a nearby hill vowed never again to fight unprepared.

The Camillan Reforms and the Invention of the Maniple Legion

After the sack of Rome by the Gauls in 390, the pragmatism which is associated with Roman civilization as a whole was applied to warfare, with Roman commanders altering the panoply and tactical formation of the legions to meet the different fighting styles of their opponents, whether barbarian or civilized. The military reforms of the early fourth century are associated with the leader Marcus Furius Camillus, a man credited with saving the city from the Gauls and remembered as a second founder of Rome. Although history cannot precisely answer if Camillus himself was responsible for the reforms, the changes that bear his name dramatically altered the character of the Roman legion in the fourth century.

As the Roman state grew at the expense of its neighbours in northern and central Italy, the Roman army expanded from three to four legions, and the number of legionaries per legion grew to perhaps 4,000 infantry. By 350 the centuries had been reduced from 100 to between 60 and 80 men apiece, and the centuries in each legion were divided among 10 cohorts for administrative reasons. The Roman army’s experience against Gauls in the north and campaigns against the Samnites (343–290) in the rough, hilly terrain of central Italy forced a change in tactical organization, one which gave individual legionaries more responsibility and greater tactical freedom.

In order to achieve maximum tactical flexibility, the Roman army abandoned the phalanx altogether in favour of the most well-articulated tactical formation of the pre-modern world. This flexible linear formation consisted of four classes of soldiers defined not only by wealth, but also by age and experience. The Greek-styled battle square was replaced by three lines of heavy infantry, the first two-thirds armed in an innovative manner with two weighted javelins, or pila, and a sword, and protected by helmet, breastplate, greaves and the traditional oval scutum favoured by the lower classes. The ranks of the forward of these two lines or hastati were filled with young adult males in their twenties, while the centre formation, or principes, comprised veterans in their thirties. The third and last line or triarii were armoured as above but for the old-style thrusting spear and scutum. The triarii consisted of the oldest veterans and acted as a reserve. The poorest and youngest men served as velites or light infantry skirmishers. Armed with light javelins and sword, and unprotected except for helmet and hide-covered wicker shield, the velites acted as a screen for their heavier armed and less mobile comrades. Each legionary was still responsible for supplying his own panoply, but in order to maintain uniformity within each century, the weapons were frequently purchased from the state.

Before battle, the hastati, principes and triarii formed up in homogeneous rectangular units or maniples of 120–160 men (two centuries probably deployed side by side), protected by the light infantry velites. Each maniple organized around a signum or standard kept by the signifer, who led the way on the march and in combat. Each maniple deployed as a small independent unit, typically with a twenty-man front and four-man depth, and may have been separated from its lateral neighbour by the width of its own frontage, though this is still a matter of some debate. Livy tells us that the maniples were ‘a small distance apart’. Moreover, the maniples of hastati, principes and triarii were staggered, with the principes covering the gaps of the hastati in front, and the triarii covering the gaps of the principes. This chequerboard formation or quincunx provided maximum tactical flexibility for the maniple, allowing it to deliver or meet an attack from any direction.

In battle the maniple legion presented a double threat to its adversaries. After the screening velites withdrew through the ranks of the heavy infantry, the hastati moved forward and threw their light pila at 35 yards, quickly followed by their heavy pila. Drawing their short thrusting Spanish swords or gladii, the front ranks of the hastati charged their enemy, whose ranks were presumably broken up by the javelin discharge. As the Roman heavy infantry thrust into the enemy, the succeeding hastati threw their pila and engaged with swords. The battle became a series of furious combats with both sides periodically drawing apart to recover. When the two formations joined, the legionaries exploited the tears and stepped inside the spears of the first rank into the densely packed mass, and wielded their swords with much greater speed and control than the closely packed spearmen could defend against.

During one of these pauses, the hastati retreated through the open ranks of the battle-tested and fresh principes and triarii. Meanwhile, the principes then closed ranks and moved forward, discharging their pila and engaging with swords in the manner of their younger comrades. If there was a breach in the Roman line, the veteran triarii acted as true heavy infantry and moved forward to fill the tear with their spears.

The new Roman system had many strengths. By merging heavy and light infantry into the pilum-carrying legionary, the Roman army gave its soldiers the ability to break up the enemy formation with missile fire just moments before weighing into them with sword and shield, in effect merging heavy and light infantry into one weapon system. Once engaged, the maniple’s relatively open formation emphasized individual prowess, and gave each legionary the responsibility of defending approximately 36 square feet between himself and his fellow legionaries, a fact which placed special emphasis on swordplay in training exercises. But even if the maniple failed, it could be replaced by a fresh one in the rear. This ability to rotate fatigued legionaries with fresh soldiers gave the Romans a powerful advantage over their enemies.

The Tarentine and Punic Wars

The Camillan military reorganization would serve the republic well in its expansion against the Samnites, Etruscans and Gauls in northern and central Italy during the fourth century bce. But Rome would face new challenges in the third century from the Greeks in southern Italy, the Carthaginians in Spain and north Africa, and Alexander’s successor states in the Levant. Rome’s martial contacts with these other regional powers would test the effectiveness of the maniple legion against combined-arms tactical systems inspired by the success of the Macedonian art of war.

The first significant test of the maniple legion came against the Greeks in southern Italy in the Tarentine Wars (281–267 bce). Rome’s expansion into the lower peninsula forced the Greeks living there to forge an alliance with King Pyrrhus (319–272), a brilliant general from the Hellenized region of Epirus, north-west of Greece in what is now roughly modern Albania. Rome’s struggle against Pyrrhus proved to be a difficult one, and over the course of the war Rome suffered two major defeats. But poor generalship, rather than an inferior fighting force, was the cause of the failures at Heraclae and Asculum in 279. But even while Pyrrhus’ forces were victorious over the Romans, his battles, especially at Heraclae, cost him dearly, giving modern historians the term ‘pyrrhic victory’ to symbolize a costly victory. The Romans finally decisively defeated Pyrrhus’ army at Beneventum in 275, and by 265 southern Italy was under Roman hegemony.

Perhaps the greatest opponent faced by Rome during its republican period was Carthage, a former Phoenician colony on the coast of north Africa (modern Tunisia) that over time developed into a formidable military and naval power. As Rome was conquering southern Italy, Carthage (called Punis in Latin) was consolidating its power in the western Mediterranean, controlling north Africa and venturing into the Iberian peninsula, Corsica and, to Rome’s dismay, the island of Sicily.

The Carthaginian presence in Sicily went back for centuries, with both Greek and Carthaginian colonists sharing the island. But after the Roman victory in the Tarentine Wars, Rome found itself at odds with Carthage over Sicily, an island Rome needed to feed its growing population. The resulting First Punic War (264–241 bce) witnessed Rome taking to the sea in order to meet the Carthaginian threat. Although the Romans did not have a history as mariners, they adapted well to naval warfare, building larger galleys than the Carthaginians and preferring grappling and boarding to traditional ramming. In fact, the Romans developed the corvus, or crow: an 18 foot gangway with a pointed spike under its outboard end. Pivoted from a mast by a topping lift, the corvus was dropped into the adjacent ship, securing it in place as legionaries crossed the plank and engaged in hand-to-hand combat with enemy sailors. The application of the corvus in naval warfare allowed Rome to fight as a land power at sea, evening the odds against an accomplished naval power.

Roman Expansion in the Mediterranean, 3rd and 2nd Centuries bce.

Although fierce storms destroyed large Roman fleets on two separate occasions, Rome eventually forced an unequal peace on Carthage. Under these terms, Carthage left Sicily under Roman hegemony and paid the Roman Republic a war indemnity. But the peace lasted less than a generation, with Rome and Carthage clashing over the fate of the city of Saguntum in eastern Spain. In the Second Punic War (219–201) the Carthaginian commander in Spain, Hannibal Barca (247–183), led an army of 40,000 troops and 37 elephants across southern Gaul, over the Alps and into northern Italy. In order to avoid a protracted war, Hannibal wanted to bring the conflict directly to Italy, defeat the legions on the field of battle and force Rome to sue for peace.

Despite heavy losses to the rigours of the long march, Hannibal defeated a Roman army at the battle of Trebia in 218. Here, Hannibal’s 19,000 infantry and 9,000 cavalry crushed a Roman army of 36,000 infantry and 4,000 cavalry. His success convinced additional Gauls to join his army. The following spring he defeated a second Roman army on the banks of Lake Trasimene. Unwilling to risk another Roman army, the Senate elected Quintus Fabius Maximus as dictator. Fabius Maximus refused to meet the Carthaginian army in battle, preferring instead a strategy of delay and harassment. Rome’s ‘Fabian’ strategy forced Hannibal to keep moving in order not to exhaust local food and forage. Unable to besiege Rome because of the absence of a siege train, Hannibal crossed the Apennines and ravaged south-eastern Italy.

Unwilling to idly watch their country razed by an enemy army, the newly elected consuls Lucius Aemilius Paullus and Gaius Terentius Varro set out with an army consisting of sixteen legions to track down and defeat Hannibal’s forces. In the summer of 216 the Romans caught up with Hannibal near the village of Cannae in Apulia. The resulting battle of Cannae pitted a Roman army of 80,000 infantry and 6,400 cavalry against Hannibal’s allied army of 45,000 infantry and 10,000 cavalry.

Hannibal camped west of the Aufidius River, while the Romans camped two-thirds of their army opposite the invading army, the remainder staying on the opposite side of the river to limit Carthaginian foraging. Varro, whose day it was to command the Roman army, lined up for battle on the east side of the river, placing his legionaries in the centre in an extra deep formation (in places, between thirty-five and fifty men deep) because of the narrowness of the plain. No more than 2,000 legionaries could engage the enemy at one time. Moreover, many of the legionaries were fresh recruits recently added to make up for the horrendous losses suffered at Trebia and Trasimene. Varro’s strategy was simple: overwhelm the Carthaginian centre with the sheer weight of his legionaries. Betting on his heavy infantry to win the day, he then placed his inferior Roman cavalry on both wings to check the advance of the more numerous Carthaginian horse.

Understanding the threat to his centre, Hannibal arranged his troops south of the Romans, placing his infantry in the centre in a convex formation and making the centre deeper than the flanks in order to match the Roman frontage and delay the legions’ advance. Hannibal kept his African infantry in reserve behind each flank of the crescent, and placed his cavalry on the flanks opposite the Roman horsemen. Outnumbered two to one in total numbers, the Carthaginian general placed his hope on his cavalry, which was superior to the Romans’ in both numbers and quality.

As was typical of classical engagements, the battle opened with skirmishing, then Varro ordered the weighted Roman centre to close with the Carthaginians. At this moment Hannibal ordered the cavalry on his wings to strike the weaker Roman cavalry opposite. As the Romans engaged with the leading edge of the Carthaginian infantry, the centre yielded to the Roman advance, slowly transforming from a convex to a concave formation. On the wings the Carthaginian cavalry routed the Roman horse on both sides. As tens of thousands of legionaries were sucked into the centre of this rapidly developing killing field, Hannibal’s African heavy cavalry ran the Roman flank and swung into the rear of the Roman army. Perhaps 60,000 Roman soldiers, including the consul Paullus, were killed, and another 10,000 soldiers were taken prisoner as a result of this classic double envelopment. So thorough was the Roman defeat that never again did the Romans risk a large field army against Hannibal on Italian soil.

The defeat at Cannae underlined the weakness of the Roman heavy-infantry-based tactical system. At Trebia the legions managed to break through the Carthaginian centre, shattering the cohesion of the enemy army. At Cannae, the Romans massed their centre, determined to break through the Spaniards and Celts forming the centre of Hannibal’s line. But this was the tactic of a pike phalanx and a misuse of Roman swordsmen. By massing the centre, the Romans were so tightly packed that they could not manoeuvre or wield their short swords effectively, especially with rank upon rank pushing from behind. The situation was further aggravated as the Romans, pushed from behind, ‘tumbled’ over their own and enemy dead, further disrupting their ranks. Hannibal’s men had no such problem as they gave way into a concave formation.

In two years, Hannibal had killed or captured between 80,000 and 100,000 legionaries and their commanders, robbing Rome of a third of its standing military force. Seemingly, the loss of three Roman armies in as many years should have satisfied Hannibal’s plans for the defeat of Rome, but once again the Roman Republic survived the deprivations of an enemy army in its midst. Without a siege train, Hannibal could not capitalize on his battlefield successes. Moreover, the strength of the Roman federation soon became apparent when none of the key allied cities in Italy betrayed their capital on the Tiber. They acted instead as islands of refuge for Roman armies between disasters. Although able to march almost at will throughout the Italian peninsula, Hannibal was incapable of bringing the Second Punic War to a decisive conclusion, and time was on the Romans’ side.

Hannibal’s luck began to change in 207, when the relief army from Spain of his younger brother Hasdrubal was intercepted and annihilated at the Metaurus River. When news of the defeat and death of Hasdrubal reached the Carthaginian army in southern Italy, many of Hannibal’s allies began to desert him. Unable to defeat Hannibal in Italy, the Romans focused on fighting other Carthaginian generals in Carthage’s sphere of influence. In 206 a Roman army under the command of Scipio the Younger (c.236–184 bce) defeated the Carthaginians in Spain, and two years later he landed at the head of a Roman expeditionary force aimed at north Africa. In 203 Hannibal was recalled from Italy in order to assemble a defence force for Carthage.

Hannibal and Scipio met at the decisive battle of Zama in 202, some 100 miles south-west of Carthage. For the first time, there was relative parity in numbers between the combatants, but the quality of Roman forces was superior to Hannibal’s army, and Scipio proved to be an experienced general who understood the full tactical capabilities of the legion on the battlefield. Scipio’s force was probably slightly inferior in infantry (he had 34,000 footmen against 36,000 Carthaginians), but was superior in cavalry after the defection of the Numidians to his side, with 6,000 cavalry against Hannibal’s 4,000 horse and 80 elephants.

Hannibal arranged his infantry in three lines. He placed his light troops and dead brother’s army in the front, hastily conscripted African levy in the middle, and his veteran army from Italy in the rear. In the very front of his infantry he placed his war elephants. Hannibal placed his cavalry on the wings, putting his heavy horse on the right and light horse on the left.

Scipio arrayed his infantry and cavalry with his legionaries in the centre and heavy cavalry on the left wing and light cavalry on the right wing. But instead of forming up his legions in the quincunx formation as was standard practice, Scipio arranged the maniples of hastati, principes and triarii directly behind and in front of one another, forming lanes through the ranks of soldiers. Scipio was careful to arrange his legions in this unorthodox manner under a screen of light infantry velites. The plan worked very well. When Hannibal initiated battle with a charge of elephants, most of them were confused by the yelling and trumpet blasts from the legions, and stampeded across the front of the armies and into their own cavalry. Those elephants that successfully reached the Roman line were goaded and herded down the lanes by velites, passing harmlessly to the rear of the legions.

Capitalizing on the confusion caused by rioting elephants pushing into the Carthaginian wings, Scipio ordered his cavalry to charge, pushing Hannibal’s horsemen from the field. Meanwhile, as the infantry closed, Hannibal’s first line was forced back by the pilum discharge and shock combat of the engaging hastati. But the African conscripts in the second line refused to admit the retreating first line, infuriating the allied Celts and Ligurians who forced their own centre or streamed around the flanks. The second line then cracked, pushing back into Hannibal’s veteran third line who, like the second line, refused to let any of their retreating comrades pass through their ranks. Perhaps fearing an overextension or outflanking, Scipio ordered a recall of his legions.

The break in the battle allowed both sides to reform. Hannibal brought his fresh veteran infantry forward in a single line, then extended their frontage. Scipio ordered his principes and triarii to the wings to counter this move, keeping his tired hastati in the centre. But Scipio, faced with a corps of veterans who had served with Hannibal in Italy for a decade and a half, did not hesitate in sending his army again into the fray. As the infantry clashed, the Roman and Numidian cavalry returned to the battlefield and charged the Carthaginian rear. Though Hannibal escaped, the Carthaginian losses exceeded 20,000 dead and perhaps 20,000 prisoners. Scipio lost 1,500 legionaries and perhaps 3,000 allied cavalry. Hannibal returned to Carthage and advised his government to sue for peace.

Carthage was never again a regional power after the Second Punic War, though Roman fears of a Carthaginian revival precipitated a Third Punic War (149–146 bce). The result of the conflict was the razing of Carthage and the division of its territories between Numidia and the Roman province of ‘Africa’. Scipio, dubbed ‘Africanus’ because of his victory at Zama, emerged as a leading statesman, while Hannibal found military appointments under various rulers in the Hellenistic East, committing suicide in 183 bce in order to avoid being betrayed into Roman hands.

Legion versus Phalanx: The Macedonian Wars

Rome’s war with Hannibal brought the Italian power into direct conflict with King Philip V of Macedon (238–179 bce), one of Alexander’s successors in the east, initiating a series of wars that eventually pulled Rome into the gravity of Hellenistic politics. The appeal of Rhodes and Pergamum for a Roman ally against the threat of an alliance between Philip V and Antiochus III of Syria piqued the Senate’s interest in the region, initiating a series of conflicts in Greece known as the Four Macedonian Wars (216–146 bce). Tactically, these wars demonstrated the superiority of the maniple legion over the fully evolved phalanx. Ever since the days of Camillus when the maniple formation was first introduced, the Roman legion, unlike the Macedonian-inspired phalanx, had developed consistently in the direction of flexibility. When these two tactical systems met on the battlefield, the result of the confrontation was usually catastrophic for the Greeks because of the vastly different capabilities of the weapon systems employed.

The historian Livy explained the psychological effects of Philip V’s first encountered with Roman infantry. In 200 bce, the Romans came to support their Athenian allies against the Macedonians. Philip’s cavalry engaged the Romans the day before and, normal to Greek warfare, the fallen were to be buried with full honours as a sort of pep rally for the coming engagement. Philip soon wished he had not agreed to the ceremony, for his soldiers were not prepared for what they saw: ‘When they had seen bodies chopped to pieces by the Spanish sword, arms torn away, shoulders and all, or heads separated from bodies … or vitals laid open … they realized in a general panic with what weapons and what men, they had to fight.’

The Greeks, used to the neat puncture wounds inflicted by javelins and pikes, were visibly shaken by the wound signature of the short Spanish sword or gladius. The gladius was slightly less than 2 feet long with a double-edged blade 3 inches in width, adopted from the short thrusting sword used on the Iberian peninsula. Slight modifications would transform this superior thrusting sword into a deadly cleaving instrument. The gladius was, according to one historian, ‘the most deadly of all weapons produced by ancient armies, and it killed more soldiers than any other weapon in history until the invention of the gun’. The gladius would be used to good effect by the Roman legionary against the sarissa-wielding phalanxes.

Three years later, at the battle of Cynoscephalae in 197 bce, Philip V was defeated by the Roman commander Titus Quinctius Flaminius in a confrontation that illustrated the superior tactical flexibility of the maniple legion. The opposing armies were almost equal in number. The Roman army consisting of 26,000 footmen (18,000 legionaries and 8,000 allied phalangeal infantry from the Athenian-led Aetolian League), 2,000 cavalry and 20 elephants. The Macedonians fielded an army of 25,500 infantry and 2,000 cavalry. The battle began as light infantry skirmishers met in the mists surrounding the Cynoscephalae hills in Thessaly. Initially, the Roman light infantry enjoyed the upper hand until Philip’s cavalry arrived, forcing the Romans to make an orderly retreat.

Seizing the high uneven ground along the ridge, the Macedonians deployed their heavy infantry phalanxes on the left wing and in the centre, then placed their cavalry on the more even ground on the right. Flaminius split his two heavy infantry legions between the centre and the right wing, with the right wing further reinforced with the Greek phalanx and a detachment of heavy cavalry and all twenty elephants. On the left wing, Flaminius placed the remainder of his heavy cavalry across from the Macedonian horse.

Philip began the battle with a downhill infantry and cavalry charge, forcing the Roman centre and left wing back. But his attack was probably premature, because it took place before his own left wing was fully deployed. Seeing this opportunity, Flaminius ordered his right plus his elephants to attack the echeloned Macedonian left, easily pushing back the still-forming phalanxes. On both sides the right wing was victorious, but an unnamed tribune tipped the scales in Rome’s favour when he peeled off twenty maniples from the Roman right and hit Philip’s centre in the rear, slaughtering the exposed phalangites. The Macedonians, in retreat, raised their sarissas in surrender, but the uncomprehending Romans cut them down. In all, Philip lost 8,000 men, while Flaminius’ losses were 700 dead.

The last great stand of the traditional phalangite army against the Romans occurred at the battle of Pydna in 168 bce against Philip V’s son Perseus. In the battle, despite being outnumbered, a Roman army inflicted a crushing defeat on the Macedonian army. By 130 bce, Rome had established hegemony over Greece, Macedon, and much of Asia Minor, and in the west, Rome conquered southern Gaul and most of north Africa before 100 bce. The reputation of Rome’s legions combined with adroit diplomacy was, at times, sufficient to win territory. Rome conquered the entire Hellenistic east virtually without fighting, relying instead on bluff and coercive diplomacy. But when diplomacy did not work, the Roman army was capable of enforcing the will of the Senate through organized violence, creating a new Mediterranean empire in the process.

The Marian Reforms

At the end of the second century bce a number of changes in the Roman army occurred that had great military, social and political implications, some of which are associated with the consulships of Gaius Marius (157–86 bce). On the military side, two of Marius’ reforms involved the conversion of the cohort from an administrative to a tactical unit by making the arms and equipment of the legion’s heavy infantry uniform, and by raising the number of legionaries in each legion from around 4,000 to 5,000 men, including support staff.

This modification in the legion’s equipment and formation was due to the increasingly large tactical array of Rome’s Germanic enemies during the second century bce. Consistent with Indo-European tradition, Germanic infantry was organized into hundreds, a group of perhaps 100 warriors who swore allegiance to a local chieftain. These formations often fought in what the Romans called a cuneus (‘wedge’), sometimes referred to as a ‘boar’s head’ wedge. This battle array placed the heaviest armoured and best-armed men in the front ranks, with lesser-armoured warriors filling in behind. This wedge formation had limited offensive articulation, but presented plenty of impact power on a small frontage. The boar’s head array was launched at an enemy in order to break up opposing formations in a single movement. If the initial attack miscarried before determined resistance, then the barbarians retreated in disorder, but if the boar’s head was successful in breaking up the opposing formation, then individual combat ensued, consistent with the Germanic fighting ethos and the reality of unarticulated heavy infantry. Furthermore, barbarian command capabilities were not sophisticated enough to be able to control more than a single body of warriors. And though they sometimes used a second line of troops, there is little evidence supporting the use of reserves.

Although the flexibility of the maniple proved adequate in battle against the civilized armies of the Mediterranean basin, its limited size of only two centuries did not allow it to meet the large Germanic battle square on equal footing. The cohortal legion would meet this need. Marrying the flexibility of the maniple to the mass of the phalanx, the cohortal legion could meet the large Germanic battle squares yet retain the tactical mobility that allowed it to deliver or meet an attack from any direction. Though it was probably used in battle before his consulships, Marius used his considerable political power to establish the cohortal legion as the standard legion. It would remain virtually unchanged for the next 300 years. Marius is also credited with making the eagle (aquila) the standard for the Roman legion.

The cohortal legion represented hundreds of years of tactical evolution. Over the course of the early and middle republic, the Roman legion was first provided with joints, then divided into echelons, then broken up into maniples only to be finally reorganized again into large, compact cohorts capable of great flexibility on the battlefield. This last evolution of the legion was attainable only by the extraordinary discipline of the Roman legionary, discipline that only increased as professionalism and length of enlistment increased. The cohort legion was organized as follows:

8 men to a contubernium – 8 men

10 contubernia to a century – 80 men

2 centuries to a maniple – 160 men

3 maniples to a cohort – 480 men

10 cohorts to a legion – 4,800 men

Under the Marian reforms the light infantry velites were abolished and became an allied responsibility fulfilled by auxiliaries. These were troops of non-Italian origin, recruited from local allied tribes and client kings. They employed the indigenous weapons of their nationality and served the Romans in the role of light infantry and light cavalry. Julius Caesar made extensive use of Gallic and, later, Germanic cavalry in his conquest of Gaul, and these same troops proved effective against Pompeii during the Civil War. Auxiliary units raised in the provinces by treaty obligations were usually led by their own commanders, with successful battle captains rewarded with Roman citizenship and titles. By the beginning of the Roman Empire (31 bce–476 ce), auxiliaries were an indispensable complement to the legion.

With the covering forces now the responsibility of allies, the Romans concentrated solely on heavy infantry. Marius replaced the thrusting spear of the third line triarii with the pilum and gladius carried by the hastati and principes, creating a standardization of arms throughout the legion. He also improved the pilum by replacing one of the two nails holding the metal head to the wooden shaft with a wooden dowel. The pilum would break on impact, ensuring that it could not be thrown back in combat. Defensively, legionaries wore articulated banded armour known as lorica segmentata, which gave them excellent protection and unprecedented mobility. The familiar rectangular scutum also reached its final form about 100 bce.

Marius also improved the mobility of the Roman army by allowing only one pack animal for every fifty men, requiring every legionary to carry his own arms, armour, entrenching tools, personal items and several days’ rations on the march. Though his load might be 80 or 90 pounds, each of ‘Marius’ mules’ was capable of travelling up to 20 miles a day over good roads and then fortifying the army camp as a precaution against nocturnal attack, a standard Roman practice when in hostile territory. Furthermore, the Romans, like the Persians, developed a very sophisticated highway system to support their armies in the field. The Romans built 50,000 miles of paved roads and 200,000 miles of dirt roads linking the provinces, giving the legionaries unprecedented strategic mobility.

The Jewish historian Flavius Josephus (b. 37 ce) tells us in his account of the Jewish revolt of 66–73 ce that when the Roman army was on the march, it usually conformed to a standard configuration, one which remained unchanged since the time of Polybius over 200 years before. Screening the column and acting as forward scouts were contingents of lightly armed infantry auxiliaries and cavalry, protecting the army from ambush. Next came the vanguard, comprising one legion plus a force of cavalry. Because the duty was dangerous, legions drew lots each day to determine which one should form the vanguard. Behind the vanguard came the camp surveyors, made of ten men from each century (or one man from each contubernium or tent). Their job was to quickly mark out the camp at the end of the day. Behind the surveyors marched the pioneer corps, engineers whose job it was to clear obstacles and bridge rivers. Next came the commanding general’s personal baggage laagers, protected by a strong mounted escort. In the middle of the column rode the general himself, surrounded by a personal bodyguard drawn from the ranks of auxiliary infantry and cavalry. Following the general were those cavalry alae organic to each legion (made up of Roman cavalry regiments consisting of 120 horsemen per legion). Next came the Roman siege train, men and mules pulling the dismantled towers, rams and siege engines necessary to attack an enemy city. Senior officers – legates, tribunes and auxiliary prefects with an escort of handpicked troops – came next, followed by the legionaries themselves marching six abreast. Each legion was headed by the aquilifer and followed by its own baggage train controlled by each legion’s servants. Behind the legions followed the rearguard, contingents of auxiliary heavy and light troops who fanned out to protect the column from rear attack. Finally, camp followers would have been found at the rear of the army, maintaining a close proximity for protection. These followers normally would have included common-law wives, children, prostitutes, merchants and slave dealers.

Frequently outnumbered on the battlefield and attacked from many angles, the legion depended for its survival on following the direct orders of the army commander. Battlefield victory and consistent performance brought great opportunity for the legionary who, over time, could look forward to promotion through the various ranks of centurion, which by the time of Marius represented a whole class of officers. Moreover, the senior centurion of a legion enjoyed considerable status, and the five senior centurions of each legion were included in councils of war held by commanders of field armies. But if the orders of a centurion were not followed and a century was judged disobedient or cowardly in battle, the entire unit was subject to decimation. One soldier in ten was selected by lot and beaten to death by his comrades, enforcing an age-old adage that the key to battlefield success is the fear of one’s own army over the fear of the enemy.

Finally, Marius dropped the property-owning qualifications for military service, opening the ranks of the legion to the lowest social class, the capite censi. Roman expansion in the third and second centuries bce created a large slave class, and consolidation of small farms into vast plantations or latifundia worked by foreign slaves eroded the class of farmer which had always been the backbone of the Roman army. These displaced rural Romans moved to the cities and became urban poor. Seeking a better life, many of these young men enlisted for longer periods of service. Under Marius, length of service was increased to six years, replacing the citizen-militia army of the earlier republic with a professional army. But, perhaps most significantly, in the unstable economic and political climate of the late republic, the allegiance of the legionaries shifted from the Roman state to individual generals, who provided their soldiers with status and booty during the territorial expansion and civil wars of the first century bce .

The professionalization of the Roman army after the Marian reforms led directly to the use and abuse of power by generals seeking to usurp the power of the Senate. Lucius Cornelius Sulla (138–78 bce), one of Marius’ generals, marched on Rome with his legions and forced the Senate to name him dictator in 82 bce. After conducting a reign of terror to wipe out all opposition, Sulla restored the constitution and retired in 79, but his use of military force against the government of Rome set a dangerous precedent. His example of how an army could be used to seize power would prove most attractive to ambitious men.

Roman Possessions in the Late Republic, 31 bce.

For the next fifty years, Roman history was characterized by two important features: the jostling for power by a number of powerful individuals and the civil wars generated by their conflicts. Not long after Sulla retired, the Senate made two extraordinary military appointments that raised to prominence two very strong personalities – Cnaeus Pompeius Magnus (106–48 bce) and Marcus Licinius Crassus (c.112–53 bce). Pompey fought for Sulla and was given military commands in Spain and the eastern Mediterranean, returning to Rome as an accomplished military hero. Crassus had also fought for Sulla, but, despite putting down Spartacus’ slave rebellion in 71 bce, he was considered more of a statesman and businessman than military commander. In 61 bce, Julius Caesar joined Pompey and Crassus in a power-sharing arrangement known as the First Triumvirate. Together, the combined wealth and political power of these three men enabled them to dominate the Roman political scene.

The elder statesman Pompey had already proved his worth as a military commander (earning a triumph while he was too young to even be a senator), and Caesar and Crassus felt compelled to win an equally impressive reputation on the battlefield. Caesar chose Gaul as his area of influence and brought the Celts under direct Roman influence between 59 and 49 bce. Crassus, hungry for military success to reinforce his political aspirations, set out for the east with plans to invade Parthia.

The Cohortal Legion at War: The Gallic Campaigns

The last major territorial expansion under the republic took place in Gaul between 59 and 49 bce. As proconsul (governor with imperium) of Gaul, Gaius Julius Caesar (100–44 bce) commanded at various times between six and eleven legions, and, counting auxiliaries (including Spanish, Gallic and German horse), the strength of his army varied between 40,000 and 70,000 men. Through many long and difficult military campaigns, Caesar used this army to bring Transalpine Gaul (the area of Gaul north of the Alps) under Roman hegemony.

Caesar’s military reputation as a great commander was made against the semi-barbaric Gauls and the more aggressive Germanic tribes who periodically invaded Roman Gaul. In his Gallic commentaries, a mostly propagandistic work on his campaigns north of the Alps, Caesar tells us of an unnamed battle in 58 bce in which perhaps 40,000 Roman soldiers and auxiliaries faced an invasion of Gaul by perhaps 150,000 Celtic Helvetii and their Germanic allies the Boii and Tulingi. Caesar intercepted the barbarian tribes as they were attempting to migrate west from their homeland east of Lake Geneva across central France. After a few successful ambushes of barbarian camps and the slaughter of thousands of migrants on the spot, the Helvetii sent an ambassador to sue for peace with the Roman general. When Caesar’s demand for damages and hostages was refused, a decisive engagement was all but assured. The two armies met at the southern edge of the rugged Morvan region in Burgundy.

According to Caesar’s account, on the day of the battle he sent his cavalry to delay the enemy’s approach and withdrew the remainder of his army to a nearby hill about 3 miles north-west of modern Toulon. He drew up the four veteran legions in his army in three lines of six ranks each halfway up the hill, and ordered his two recently levied legions and remaining auxiliaries troops to the summit, quickly converting the hilltop into an earthwork fortification and base camp. Caesar then ordered all of the officers’ horses taken to the summit so that no one could entertain the idea of retreat. The Helvetii were the first to arrive before the Roman position and, without waiting for reinforcements, attacked the Romans. The Romans used their advantage in elevation to rain pila down on the Germans, stopping the enemy advance in its tracks. Then the veteran legionaries drew their swords and advanced down the hill. Though the Helvetii resisted, they were finally forced to begin a slow fighting withdrawal toward a hill a mile away. Just as the Helvetii gained the safety of the hill, warriors from the Boii and Tulingi appeared on the right flank of the advancing Roman legions and threatened their rear. Seeing the arrival of their allied tribes, the Helvetii once again pressed forward.

Faced with a crisis, Caesar ordered his Romans to form a double front, the first and second lines to oppose the Helvetii counter-attack, and the third line to form a new front at an angle to the first in order to face the newly arrived enemy. The battle, fought in two directions, continued from early afternoon until evening, with Caesar recording in his commentaries that not a single Gaul was seen running away. But finally, after suffering perhaps 20,000 casualties, the Helvetii and their Germanic allies gave way before the Roman advance, abandoning their camp and baggage, and taking flight under the cover of night. Though Caesar gives no figures on Roman casualties in this unnamed battle, he does state that the Roman army remained on the battlefield for three days in order to bury their dead, treat the wounded and rest before pursuing the Germans. This victory forced most of the survivors back to their lands to act as a barrier against other barbarian tribes attempting to cross the Rhine.

Legion versus Cavalry: The Battle of Carrhae

In the second century bce the Parthians carved out a south-west Asian empire at the expense of the Seleucid kingdom, one of Alexander’s successor states. As horse nomads from the Eurasian steppe, the Parthians brought with them a strong equestrian tradition. The Parthian army was a cavalry force, consisting of light cavalry horse archers supplemented by noble lancers or cataphracts (from the Greek meaning ‘covered over’), chain- or scale-mailed heavy cavalry whose ancestors reached back to the well-armoured Persian cavalry of Cyrus the Great.

Parthian light cavalry wore little or no armour, instead relying on mobility and ‘hit and run’ tactics. The standard Parthian horse archer practice was to canter in loose order toward the infantry enemy. At 100 yards the formation broke into a gallop and fired arrows. At about 50 yards (still out of range of most light infantry javelins), the formation wheeled right and, still firing, rode along the front of the enemy formation. Alternately, they reined in and skid-turned, then fired more arrows over their shoulders as they retreated out of enemy archer range. This last manoeuvre became known as the ‘Parthian shot’, although all Eurasian horse archers practised it. These charges and volleys continued all day, with swarms of horse archers darting in and out of dust clouds, and were designed to wear down defending infantry squares. Moreover, the Parthians were masters of the ruse and adept in the feigned retreat, pulling enemy cavalry into pursuit, then ambushing them far from their camp.

Marcus Crassus was an experienced general, having served under Sulla in the 80s and gained notoriety as the commander who finally put down Spartacus’ revolt in 71 bce after it had defeated numerous Roman armies and pillaged the Italian countryside. But defeating a slave revolt did not earn him the most coveted reward in Rome – a triumphant parade. Instead, the Senate awarded Crassus the governorship of Syria, and he intended to use this position to push Roman hegemony east into Mesopotamia at the expense of the Parthians, despite a peace treaty between the two empires. At sixty years of age, he realized that this was his last chance to become the worthy heir of Pompey.

On his march toward the old Hellenistic capital at Seleucia in Mesopotamia, Crassus occupied numerous Parthian frontier towns, provoking an angry response from the Parthian king. The Roman army encountered the Parthian host near Carrhae. Although many of the Romans wanted to rest there, Crassus, urged by his son Publius, decided to march on. Publius was an aggressive commander in search of a military reputation of his own who had served with distinction under Julius Caesar in Gaul.

Unfortunately for the Romans, their slow moving, infantry-based army soon attracted a Parthian force consisting of 1,000 cataphracts and some 8,000 horse archers, led by the capable Parthian general Surena. Crassus, recognizing the unfavourable strategic situation evolving around his army, formed up his troops into a battle square, placing his seven legions (28,000 men), 4,000 light troops and 4,000 allied cavalry around his baggage train as the Parthian horse archers surrounded and attacked the defending Romans (Map 4.7(a)). According to Plutarch, the situation was dire:

The Parthians stood off from the Romans and began to discharge their arrows at them from every direction, but they did not aim for accuracy since the Roman formation was so continuous and dense that it was impossible to miss. The impact of the arrows was tremendous since their bows were large and powerful and the stiffness of the bow in drawing sent the missiles with great force. At that point the Roman situation became grave, for if they remained in formation they suffered wounds, and if they attempted to advance they still were unable to accomplish anything, although they continued to suffer. For the Parthians would flee while continuing to shoot at them and they are second to this style of fighting only to the Scythians. It is the wisest of practices for it allows you to defend yourself by fighting and removes the disgrace of flight.

The Parthians continued to harass the Romans with their ‘hit and run’ tactics, and were resupplied by camel with more arrows in order to keep the pressure on.

Crassus tried to subdue the Parthian light cavalry with his allied auxiliaries, but their numbers were insufficient to deal with the mounted archers, and they were eventually forced back to the legionaries’ lines. Understanding that his army was slowly losing the battle of attrition, Crassus sent forward his son Publius with eight cohorts, 500 archers and 1,300 cavalry, including a contingent of Gallic lancers (Map 4.7(b)). The Parthians yielded to the Roman sally and Publius gave chase. But Publius’ forces were surrounded by Parthian lancers and horse archers, and, separated from the Roman main body, annihilated. Publius’ head was taken back to the Roman camp to taunt Crassus. Night fell and the Parthians withdrew. Under cover of darkness, the Romans retreated back to Carrhae, leaving behind an estimated 4,000 wounded, who were butchered by the enemy the following morning. During the night, another four cohorts lost contact with the main force and were cut down by the Parthians.

Crassus and 500 of his cavalry made it back to Carrhae, while the remainder of Crassus’ forces retreated to nearby mountains. But the Romans in the mountains abandoned their strong position to aid Crassus. Realizing that the Roman leader might escape, the Parthian commander, Surena, invited Crassus to a parley, where he and his officers were killed. Total Roman losses were 20,000 killed and perhaps 10,000 captured. Ten thousand Roman troops did manage to escape to Roman territory. It was the worst Roman loss since Cannae.

Crassus’ defeat at Carrhae illustrated the danger of bringing a poorly balanced combined-arms system into a hostile environment. The Roman army entered the flat plain of Mesopotamia with insufficient cavalry and light infantry. Unable to punish the Parthian light cavalry with their own archers, the Roman legionaries were forced into defensive battle squares and picked off by the enemy horse archers. The Parthian victory clearly demonstrated the superiority of the light cavalry weapon system over heavy infantry when campaigning on terrain that favoured horses. Although heavy cavalry assisted the Parthian victory, the light cavalry horse archers could have won the battle against poorly supported Roman heavy infantry unaided.

The Augustan Reforms

Octavian’s victory at the battle of Actium in 31 bce ended nearly a century of turmoil and civil war. Taking the name Caesar Augustus (the ‘exalted one’), he understood that nothing had contributed more directly to the failure of the republic than the growth of client armies and the inability of the Senate to control their commanders. Augustus was determined that the same fate would not befall his own regime. In order to stop this dangerous trend, he set about designing a system under which the Roman army would be clearly subordinate to him alone. To do this, he combined the title of Imperator (originally reserved for commanders of victorious Roman armies) with the consular powers of commander-in-chief, from which evolved the title ‘emperor’. As both head of state and commander-in-chief, Augustus enjoyed a double hold over provincial governors. He took further precautions by transferring these governors at least once every four years, reserving the more sensitive commands for his relatives, and personally controlling all important promotion, rewards and pay rises in the army.

During Augustus’ reign, the Roman army was reduced from the sixty legions left after Actium to 300,000 men in total, consisting of 150,000 Roman citizens in twenty-five legions and 150,000 non-citizens in auxiliary infantry cohorts and cavalry regiments. For the next 200 years the number of legions varied between twenty-five and thirty, not a large army for an empire that contained nearly 60 million people. Under Augustus, the length of enlistment changed dramatically, increasing from six to twenty years, with a further five years required for veterans retained as officers. The reason for this increased service was probably financial, because the pressure of providing grants of land or money to discharged soldiers was very taxing to the empire, so an extended enlistment was required to ease the economic burden.

The Roman Empire under the Pax Romana.

Augustus did not modify the tactical organization instituted by the Marian reforms. The Augustan legion still consisted of ten cohorts, but some time in the middle of the first century ce, the strength of the first cohort was doubled to five centuries of 160 men. Perhaps this was done to provide the legion with a larger tactical formation when dealing with barbarians, or as a tactical reserve. Augustus did, however, make a regiment, or ala, of 120 cavalrymen organic to each legion. These men were drawn from the ranks and mounted as scouts (exploratores) and messengers. The early Roman cavalry was lightly armoured and capable of limited shock and missile action. But the role of Roman cavalry on the battlefield increased because of prolonged contacts with cavalry-based tactical systems in the east, and in the early second century the Roman emperor Trajan raised an ala intended purely for shock combat. Using the two-handed lance or kontos, these heavy cavalrymen could not make effective use of a shield, so heavier armour was worn, modelled after the Persian cataphracts. Called clibanarii, these lancers and mounts were protected by composite chain- and scale-mail armour. As the empire wore on, clibanarii formed an increasingly higher proportion of Roman cavalry and would become the dominant tactical system of the later Byzantine Empire.

The role of the auxiliary also increased in importance in the early imperial period, with the auxiliary’s organization and number becoming standardized under Augustus. During the Civil Wars auxiliary units varied in size and there was no set total of units authorized. Under Augustus, the number of auxiliary troops rose to a number roughly equal to that of legionary troops. Auxiliary cohorts and alae contained about 480–500 men, and were called quingenaria, or ‘500 strong’. It was not until after the emperor Nero (r. 54–68) that this number rose to 800–1,000 men, called cohortes milliariae and alae milliariae (‘thousand strong’). In addition, an auxiliary cohort made up of a mix of both infantry and cavalry units was created (cohortes equitatae), with the proportion of these mixed units probably close to four to one infantry to cavalry.

As the empire wore on, auxiliary units gained significant influence within the Roman war machine’s command structure. Initially commanded by their own chieftains, the Augustan reforms placed auxiliary troops under Roman commanders. Over time, the value of the auxiliary on the battlefield could be seen by the prestige associated with commanding these troops. The title of tribunus was granted to the commander of the auxiliary cohors milliaria, a title equal in seniority to that of a tribune of a legion.

Augustus also created a new imperial grand strategy, placing Roman legions in a forward position on the frontiers, far away from Rome itself. This grand strategy emphasized a fortified and guarded border or Limes, placing the legions in perpetual contact with the barbarians and ensuring that the Roman legionary was always in a high state of training and readiness. The Limes system also helped keep the legions far from the Roman capital and away from imperial politics.

To protect himself and ensure domestic tranquillity in Rome, Augustus created a personal bodyguard called the Praetorian Guard consisting of nine double-strength cohorts. The guardsmen were organized, trained and armed like the regular legionaries, but were handpicked men of Italian origin who were paid three times as much as normal Roman soldiers, and received benefits after only sixteen years of service. The Praetorian Guard was the only fighting force stationed in Italy. Augustus originally organized the guard so that only three cohorts would be in Rome; the other six were to police the hinterland, with rotation back to Rome each spring and autumn. But after Caesar Augustus’ death in 14 ce, this rotation fell apart and the majority of the guard stayed at home, where they often participated in the selection of future emperors. In fact, four of Rome’s emperors were elevated to the purple from the ranks of the Praetorian Guard.

Further Roman expansion was blocked in the Near East by Parthia, but Augustus used his legions to put down revolts in the Roman provinces of Iberia and Illyria, and launched expeditions into Dacia (modern Romania) and against German tribes east of the Rhine. Augustus’ campaign across the Rhine ended in disaster when a Roman army consisting of three legions ventured into northern Germany in 9 ce and was ambushed by a large force of German tribesmen in the Teutoburg Forest. In this battle, the Roman heavy infantry legionary would face a capable and determined Germanic foe utilizing light infantry tactics.

Legion versus Light Infantry: The Battle of Teutoburg Forest

In 6 ce Augustus sent Publius Quintilius Varus to keep the peace in the newly occupied region of Germania, an area east of the Rhine River in what is now modern Westphalia. Though it was pacified after nearly twenty years of occupation, the Romans maintained a strong base at Aliso (modern Haltern) defended by three legions, XVII, XVIII and XIX (18,000 infantry and 900 cavalry), and allied auxiliaries (3,500–4,000 allied infantry and 600 cavalry), perhaps 23,500 troops all together. The atmosphere in Germania was calm in the autumn of 9 ce, and the legions were used to Romanize the region, felling trees and building roads and bridges.

In September the calm was broken by a minor insurrection of Germanic tribesmen. Setting out for his winter quarters at Minden, Varus decided to pass through the troubled region. But unknown to him, the insurrection was orchestrated by one of his own military advisers, Arminius, a man of Germanic birth who had been granted Roman citizenship and held equestrian rank. Arminius engineered this uprising in order to draw Varus through what appeared to be friendly but difficult terrain, with the intent of annihilating the Roman forces. Although tipped off about the possible plot by a subordinate officer, Varus disregarded the threat and marched south-west with his army in column, followed by a long baggage train and the soldiers’ families.

On the second day out, Arminius and his Germanic contingent suddenly disappeared from the Roman column. Shortly thereafter, reports reached Varus that outlying detachments of soldiers, probably scouts and foragers, had been slaughtered. Fearing an ambush in hostile territory, Varus then turned his column and headed south toward the Roman fortress of Aliso. The march to Aliso would take the encumbered column through the Doren Pass in the Teutoburg Forest, between the Ems and Weser rivers. Here, the manoeuvrability of the column was severely limited by thick woods, marshes and gullies, exacerbated by seasonal rains and the presence of the heavy baggage train and camp followers.

The first attack on the Roman column took place as Roman engineers were cutting trees and building causeways in the difficult terrain. Despite the disappearance of Arminius and his men, Varus refused to take any special security precautions. Instead, the troops were thoroughly mixed in with the civilians. As the column slowed and piled up, the wind surged and the rain began.

In the midst of this confusion, Arminius suddenly struck the Roman column’s rearguard as his Germanic allies emerged from the woods on the Romans’ flanks, hurling javelins into the mass of the unformed Roman ranks. Varus ordered his own auxiliary light infantry to engage the barbarians, but these troops were Germanic to a man and, either seeing the futility of the situation or in a prearranged plot, deserted the Romans to join Arminius’ forces. Gradually, the legions formed, but not before taking significant casualties. As the Roman column’s vanguard prepared for a counter-attack, the German attackers disappeared as quickly as they had appeared. Roman engineers sallied out and found some flat, dry terrain and began to construct a field camp. As the Roman column made its way to the safety of the camp, Varus ordered his supply wagons burned and nonessential supplies abandoned.

At dawn Varus set out again, this time with his army in field marching formation (Map 5.2(d)). His objective was Aliso, now less than 20 miles away through the Doren Pass. As the Roman column marched out of the forest and into open terrain, Arminius’ troops shadowed the invaders, skirmishing with the Romans at every opportunity, but refusing to engage in force. The barbarians hurled their javelins into the Roman ranks to good effect, but without their own light infantry they could not return fire. The situation became worse when the column entered the woods. The barbarians attacked again as they had the day before, hurling javelins from the woods and engaging in small-unit attacks when the terrain and numbers favoured them.

At day’s end, the Romans built a second field camp about a mile from the opening of the Doren Pass and tended their wounded. Unfortunately, Varus did not fully understand the magnitude of his strategic situation. Every major Roman outpost east of the Rhine had been attacked, and most were overrun. Aliso, his objective, was besieged by Germanic tribesmen and was barely holding on. Meanwhile, Arminius’ forces were swelling, and soon he had enough troops to successfully overrun the Roman camp.

Arminius spent the night felling trees to obstruct the floor of the ravine, forcing the Romans to slow their march and fight for every foot of passage through the pass. The Germans then took up positions on the hillside and prepared for the Romans. The following morning, Varus pushed toward the Doren Pass. As the Romans pressed up the pathway, they began to meet heavy resistance from Germanic light infantry hailing down missiles from the hillside. The Romans gradually gained ground, but when a heavy rain began, the slick surface slowed the Romans’ ascent.

Finally, unable to secure passage through the pass in the face of inclement weather and a determined foe, the Romans in the van began a controlled retreat down the ravine. At this moment, Arminius ordered a general attack, sending his infantry into the ravine to meet the Romans in hand-to-hand fighting. Germanic swords and javelins struck at Roman cavalry, forcing the horses back into the Roman infantry. In the midst of the mounting confusion, Varus ordered a retreat to the base camp. The Roman retreat, which began in good order, turned into a general rout. Some Roman cavalry broke away from the column and rode into open terrain, only to be run down by Germanic cavalry. Back in the ravine, the barbarians cut the column in several places, isolating and then overwhelming the Roman units. A contemporary historian of the battle notes that the Roman army ‘hemmed in by forests and marshes and ambuscades was annihilated by the very enemy that it had formerly butchered like cattle’.

At Teutoburg Forest, three Roman legions and 10,000 camp followers were killed during two days of intensive fighting. Like the battle of Carrhae half a century earlier, the Romans lost because they were unable to compel their enemy to meet them in close-quarter combat. The Germanic light infantry used terrain to good effect, ambushing the Romans and attacking at a distance with javelins, then disappearing back into the forest. This form of ‘hit and run’ tactic wore down the Romans, forcing the legions, in the words of recent authorities on the battle, to ‘die a death of a thousand cuts’. When close battle was finally offered, the Roman heavy infantry was in full retreat, discouraged, disorganized and overwhelmed by a numerically superior foe. But even under these dire circumstances, the Romans fought in small units for hours, meeting and beating wave after wave of barbarian attackers. One small troop of legionaries fought on throughout the day and into the next, being overcome by the barbarians the following morning and killed on the spot.

As a consequence of this defeat, the Romans never occupied more than the fringe areas of Germania, instead relying on the Rhine and Danube rivers as a natural barrier demarcating the Roman Empire’s northern border. Territorial expansion did take place under the successors of Augustus, but with the exception of the annexation of Britain by Claudius (r. 41–54 ce) in 43 ce, the expansion remained within the natural frontiers of the empire – the ocean to the west, the rivers to the north and the desert in the east and south. Still, three areas prompted special concern. In the east, the Romans used a system of client states to serve as a buffer against the Parthians. In the north, the Rhine–Danube frontier became the most heavily fortified frontier area because of the threat from Germanic and Asiatic tribes, while in the north-west, Britain served as a safe harbour for Celtic tribes, prompting the Romans to cross the English Channel and challenge the barbarians for mastery of the island.

Legion versus Chariots: The Roman Campaigns in Britain

Rome’s first foray into Britain took place in August 55 bce when Julius Caesar led two legions in a reconnaissance expedition against the Celtic tribes. By then three years into a very successful Gallic campaign, Caesar set his sights on the relatively unknown island on the edge of the known world, perhaps wishing to secure a piece of the tin trade or possibly to gain more political fame in Rome by subduing yet another foe. Caesar returned to Britain in the following summer with five legions, landing north-east of Dover in modern Kent. Pushing through weak resistance on the beachhead, Caesar marched inland and crossed the Thames River near Brentford. The British chief Cassivellaunus avoided a large battle against the Romans, instead harassing the invaders with war chariots and cavalry raids.

This meeting between Roman legion and Celtic chariots was in essence an encounter between the finest Iron Age army of the classical period and a battlefield anachronism whose origins dated back to the Bronze Age. Yet, despite never meeting the Britons in a pitched battle, Caesar was impressed with the barbarians’ chariots, describing their harassing tactics in his Gallic Wars:

They begin by driving all over the field, hurling javelins; and the terror inspired by the horses and the noise of the wheels is usually enough to throw the enemy ranks into disorder. Then they work their way between their own cavalry units, where the warriors jump down and fight on foot. Meanwhile the drivers retire a short distance from the fighting and station the cars in such a way that their masters, if outnumbered, have an easy means of retreat to their own lines. In action therefore, they combine the mobility of cavalry with the staying power of foot soldiers. Their skill, which is derived from ceaseless training and practice, may be judged by the fact that they can control their horses at full gallop on the steepest incline, check and turn them in a moment, run along the pole, stand on the yoke, and get back again into the chariot as quick as lightning.

Perhaps recognizing the capabilities of Caesar and his veteran legions, Cassivellaunus finally agreed to peace terms at Verulamium (modern St Albans, 20 miles north-west of London), surrendering hostages and agreeing to pay tribute to Rome. Satisfied, Caesar retraced his route to the coast and re-embarked for Gaul. The expedition achieved no permanent gain for Caesar (no tribute was paid or significant plunder gained) and Britain remained outside of Roman imperium for another ninety-seven years.

Emperor Claudius’ invasion of Britain in 43 ce marked the beginning of a four-century period of occupation and Romanization. The British Celts, politically divided, offered only temporary resistance to the four legions sent by the emperor to pacify the island. In the years following the Roman invasion, these legions repeatedly breached the Celtic defences, storming hilltop fortresses and occupying first the south-eastern lowland zone and finally, after some difficulty, the highlands in northern England and westward through Wales to the Irish Sea. The greatest challenge to Roman occupation took place in 61 ce when several Celtic tribes rebelled against harsh and humiliating treatment by the Romans in East Anglia, initiating a killing spree of all foreigners in their wake. Led by the red-headed Boudicca, the widowed warrior queen of the Iceni tribe, the Celts first attacked the undefended town of Camulodunum (near modern Colchester), slaughtering the Roman settlers and those Britons collaborating with the enemy.

Rushing from its barracks in Lindum (modern Lincoln) to put down the revolt, the IX Legion was overcome by the sheer numbers of the Celtic tribesmen and annihilated. At Glevum (modern Gloucester), the commander of the II Legion, Poenius Postumus, refused to leave the protection of his encampment, while the other two legions in Britain, the XIV and XX under provincial governor Suetonius Paulinus, were in Wales. Before the Welsh legions could intervene, Boudicca’s rebels attacked Londinium (London), murdering its inhabitants and burning the small Roman city to the ground. The rebels then turned to the north-west and destroyed the city of Verulamium. As many as 70,000 people are estimated to have been killed in the three massacres.

In a forced march from Wales, governor Paulinus’ two legions arrived outside Verulamium and took up position in a strong defensive position in a large defile. With his flank and rear secured by heavily wooded hills, the Roman commander arrayed his infantry (6,000 legionaries and 4,000 auxiliaries) in the centre in a slightly concave formation, with cavalry alae (500 men each) on the wings, and light infantry on the flanks. The Romans, drawn up in their defile, watched as masses of Celtic chariots, cavalry and infantry filled the plain before them, followed by wagons and carts filled with booty from the sacked towns. Assured of victory, the Britons also brought with them their women and children so that they might witness the destruction of their Roman overlords. A modern estimate places the total British force at between 40,000 and 60,000 men, with perhaps another 40,000 spectators. Tacitus tells us that on the British side, ‘cavalry and infantry bands seethed over a wide area in unprecedented numbers’. Whatever the actual figure, the Romans were outnumbered at least four to one, and probably by a larger ratio.

Classical writers tell us very little about the progress of the battle of Verulamium, leaving modern historians to speculate on its course and the veracity of casualty figures. According to custom, the Britons placed their war chariots in the front of their army, where they drove up and down their adversary’s ranks, hurling insults and javelins into their enemy’s lines in a hope of taunting their opponents into breaking their formation. Whether this was tried at Verulamium is unknown, but contemporary accounts tell us that the Romans did not break ranks, staying safe behind their own shield walls and returning fire with their own light and heavy pila as the huge barbarian host neared.

When the Romans finally counter-attacked, they adopted a series of wedge formations and, with auxiliary archers in support, pushed forward from the defile. As the legionaries advanced, hacking and thrusting their way through the unarticulated masses of barbarians, their wedge formations quickly consumed the precious ground between them and their enemy, pressing the Celtic chariots, cavalry and infantry into one another. The British lines broke and a rout ensued. Any hope of retreat was thwarted by the enormous crowd gathered to watch the battle. Caught between the Roman killing machine and their own wagon laager, the Britons were slaughtered by the tens of thousands. No quarter was given to man, woman or child. Roman sources claim 80,000 Britons were killed, while Roman casualties were just over 400 dead and a similar number wounded.

Having escaped the massacre at Verulamium, Boudicca took her own life with poison, while the Roman commander at Glevum, Poenius Postumus, fell on his sword in disgrace. Over the next few centuries, Roman Britain would enjoy unbroken peace and prosperity, with Roman institutions gradually penetrating Celtic and pre-Celtic cultures. The Roman army pushed the frontiers northward to the borders of Scotland, building first Hadrian’s Wall, a defensive structure 80 miles long across northern England, and later Antonine’s Wall in the second century to keep the Picts in Scotland at bay. But the expense of keeping 10 per cent of the Roman army garrisoned in this far-off province proved too costly for the empire. After the barbarian penetrations of 410 ce, the British legions were recalled to the continent, leaving the heirs of four centuries of Romanization to fend for themselves. Attacked from the west and north by the Irish and Celts, and from the east by the Angles and Saxons, the Romano-British would finally succumb to the invaders. By the early medieval period, Roman Britain would be quickly transformed into Anglo-Saxon England.

The Roman Limes Threatened: The Return of Civil War and Invasion

At the beginning of the second century, Emperor Trajan (r. 98–117) broke with Augustus’ policy of defensive imperialism by extending Roman rule into Dacia, Mesopotamia and the Sinai peninsula. Trajan’s conquests represent the high-water mark of Roman expansion. His successors recognized that the empire was overextended and pursued a policy of retrenchment. Hadrian (r. 117–138) withdrew Roman forces from much of Mesopotamia and, though he retained Dacia and Arabia, went on the defensive in his frontier policy, reinforcing the Limes along the Rhine–Danube frontier and building the wall in England that bears his name. By the reign of Marcus Aurelius (r. 161–180), the vulnerability of the empire had become apparent. Frontiers were stabilized, and the Roman forces were established in permanent fortresses behind the frontiers.

Although the Limes system was strengthened in the second century, the Roman army remained the primary instrument for the defence of the frontiers. In 14 ce it numbered twenty-five legions, but increased to thirty by the time of Trajan at the beginning of the second century ce. The auxiliaries were increased correspondingly, making the imperial army a force of about 400,000 soldiers in total (legionaries and auxiliaries) by the end of the second century. Since legionaries were required to be Roman citizens, most recruits in Augustus’ time were from Italy. But in the course of the first century, the reluctance of Italians to enlist in the military led to the recruitment of citizens from the provinces. By the middle of the first century, 50 per cent of the legionaries were non-Italian, and by 100 ce, only one in five was Italian. In the second and third centuries, more and more recruits came from the frontier provinces than from the more Romanized ones.

The death of Marcus Aurelius in 180 ce marked the end of the Pax Romana and the beginning of more than a century of militarism and civil war. Decline was temporarily halted under the reign of Publius Septimius Severus (r. 193–211) and his heirs. Severus created a military monarchy, viewing his legions as his ultimate source of authority. He abolished most of the remaining class distinctions in the army, raised its pay by a third and broke with tradition by stationing a legion in Italy in order to have a strategic reserve. Moreover, the army itself was expanded to thirty-three legions, and military officers were appointed to important government positions.

Military monarchy was followed by military anarchy. For a period of almost fifty years (235–284), the Roman Empire was mired in almost continuous civil war. Adding to the effects of the growing chaos within the Roman government was the increasing threat of barbarian invasion into Roman territory. In 250 the Goths penetrated the Roman Limes and raided as far south as Greece, annihilating a Roman army in Thrace led by the emperor Decius. The Franks advanced into Gaul and Spain, and the Alemanni even invaded Italy itself (the city of Rome was fortified for the first time since the Punic Wars). Moreover, military commanders took advantage of the chaotic conditions and seized areas in Gaul, Syria, Egypt and Anatolia. It was not until the reign of Emperor Aurelian (r. 270–275) that most of the boundaries were restored. Although he abandoned the Danubian province of Dacia, he reconquered Gaul and re-established order in the east and along the Limes.

Invasions, civil wars and plague brought back from the east by legions led to a considerable loss of population and a shortage of military manpower in the third century. Also, financial strains made it difficult to enlist and pay the necessary soldiers. Whereas in the second century the Roman army was recruited from citizens in the provinces, by the mid-third century, the state was relying on hiring barbarians to fight under Roman commanders. These soldiers had no understanding of Roman traditions and no real attachment to either the empire or the emperors. The ‘barbarization’ of the Roman army had begun.

The Late Empire: The ‘Barbarization’ of the Roman Army

By Aurelian’s reign, Roman units on the frontiers were undergoing a profound transformation, one that fundamentally changed the character and appearance of the Roman imperial army. Mobile elements of the army were increasingly mounted in order to meet and defeat the barbarian incursions. The increased presence of non-Romans within the ranks of the army led to the inclusion of eastern and Germanic arms, armour and fighting methods within the Roman army. In the eastern provinces, a new Roman heavy cavalry was introduced, modelled after the Persian cataphracts. By the late imperial period there is evidence that in the eastern provinces the Romans sometimes armed their shock cavalry with bows or used auxiliary light cavalry (equites sagittarii) armed with the Asian composite bow to supplement their tactical mix.

In the course of the third century, the Roman Empire came close to collapse. At the end of the third and beginning of the fourth centuries, it gained a new lease of life through the efforts of two strong emperors, Diocletian (r. 284–305) and Constantine the Great (r. 324–337), who restored order and stability. The late empire’s ‘Indian summer’ began when Diocletian split the state into eastern and western zones (Map 5.4) and appointed a fellow augustus (co-emperor) and two caesars (deputy emperors) to govern in a tetrarchy (rule by four). Diocletian also returned to a preclusive strategy that advocated stopping invasions along the frontiers. To do this, he divided the empire into military districts administered by a vicar. Each district was somewhat self-contained, with its own pay, supply and militia structure. Diocletian then increased the size of the army to between 400,000 and 500,000 men, and added specialized infantry units to the legion, including the Ioviani and Herculiani and heavy cavalry lancers (lanciari). These arrangements made governing the empire easier, but they also set the stage for a permanent political and cultural split, one that would ultimately create the Byzantine Empire centred on Greece in the east, and a weakened Western Roman Empire centred on Italy in the west. Diocletian’s abdication in 305 precipitated another civil war, and complete order was not restored until Constantine united east and west in 324.

Under Constantine a switch in emphasis in Roman grand strategy was finally completed, a change that compromised the integrity of the Roman tactical system and opened the door for a full-scale ‘barbarization’ of the Roman imperial army and the final demise of the legion. During this period, Roman grand strategy moved away from its traditional static frontier defence toward a defence-in-depth. Since the reign of Augustus, imperial grand strategy placed Roman legions in a forward position on the frontiers, far away from Rome itself. Because of perpetual contact with the barbarians, the Roman legionary was always in a high state of training and readiness, a fact that helped ensure peace and prosperity in the empire for centuries. But plague and endemic political chaos in the third century eroded the Roman Empire’s ability to defend itself against the barbarian tribes massing on its borders. In response to this increased threat, Constantine implemented a change in grand strategy when he unified the empire. His solution to barbarian penetrations was a change from a linear defence to a defence-in-depth posture. This grand strategy favoured a central reserve of troops with great mobility, with cavalry preferred to infantry. Strong points on the border would serve as pockets of resistance to slow, pin and harass the enemy while the mobile reserve moved in and counter-attacked. The mobile army was a large force of perhaps 100,000 men commanded by two field marshals, a commander of the infantry (magister peditum) and the commander of the cavalry (magister equitum).

Diocletian’s Reorganization of the Empire.

Since the defence in depth required greater mobility to be effective, the cavalry’s position in the Roman army was raised. Emperor Gallienus (r. 253–268) probably initiated the mobile field army in the mid-third century, raising the stature of cavalry in the Roman army and stationing the cavalry force in Milan. Gallienus also increased the legion’s organic regiment from 120 horsemen to over 700, paving the way for the demise of the traditional infantry-based Roman army. But this cavalry reserve was probably not a permanent force. It would be during the reign of Constantine (r. 324–337) that a permanent mobile army was formed. He went so far as to disband the Praetorian Guard, replacing it with elite cavalry palatini regiments, recruited mainly from the Germanic tribes. With the emergence of cavalry the position of Roman infantry began to erode, and traditional Roman infantry tactics, driven by harsh discipline and constant training, simply disappeared. The Romans even adopted the Germanic war cry, the baritus, when in battle. The deterioration of the emperor’s army would have ominous results when Roman infantry proved unable to beat barbarian infantry on the battlefield at Adrianople in 378, Pollentia in 402 and Rome in 410.

By the beginning of the fourth century the legion completely disappeared, replaced by the palatini, comitatenses and limitanei in order of importance. The palatini were the emperor’s guard, cavalry regiments chosen by merit and replacing the Praetorian Guard. The comitatenses made up the field army, comprising mixed regular and barbarian regiments, while the limitanei were a militia, retired legionaries mustered to defend their homeland. In times of emergency, limitanei could be promoted into the field army, receiving the title pseudocomitatenses. The complement of these new units was about one-third of a first-century legion. While Septimius Severus commanded 33 legions in the early third century, by the end of the fourth century there were 175 of these smaller formations.

Further evidence of the ‘barbarization’ of the Roman military can be seen in changes in weapons and armour. The Roman soldier’s offensive arms of heavy and light pila and gladius were replaced by the Germanic thrusting spear and a longer slashing sword or spatha, a straight two-edged sword used by both infantry and cavalry. Though the spatha was pointed for thrusting, it was usually utilized for cut-and-slash strikes, emulating the favoured tactics of the Germanic tribes. ‘Barbarization’ also affected the defensive characteristics of the Roman soldier. By the early fourth century, body armour was almost completely abandoned by Roman infantry. The Roman soldier’s protection came from his shield, a Germanic-inspired round or oval shield that replaced the rectangular scutum of the early empire. Consistent with Germanic practices, heavy cavalry continued to wear mail shirts and metal helmets. By the end of the fourth century, both weapon quality and weapon training had deteriorated drastically from earlier standards.

Constantine’s conscious adoption of a defence-in-depth strategy in the early fourth century increased the importance of cavalry, giving Germanic equestrians greater leadership opportunities in the Roman army. With this increased influence came the natural adoption and adaptation of Germanic arms and armour at the expense of the traditional Roman panoply, leading to greater ‘barbarization’ of the Roman army. Two significant examples of the ramifications of this ‘barbarization’ of the Roman military machine came in the late imperial period with the battles of Adrianople in 378 and Châlons in 451.

Roman Infantry in Decline: The Battles of Adrianople and Châlons

After Constantine’s reign the Roman Empire continued to be divided into western and eastern parts, with the Western Roman Empire coming under increasing pressure from invading barbarian forces, while the Eastern Roman Empire faced the emerging power of the Sassanid Persians. Emperor Julian the Apostate (r. 361–363), so named because of his refusal to adopt the rising religion of Christianity, faced a difficult strategic situation with Persia. Though Julian’s army was tactically proficient, he misused its capabilities, losing his life in a battle a few miles from Maranga on the Tigris in 363. His successor, Jovian (r. 363–364), negotiated a humiliating peace with Persia, ceding northern Mesopotamia to the Sassanid rulers. The loss of an emperor on the battlefield would have deep psychological effects, and unfortunately for the Romans, he would not be the last Roman ruler killed in action. Fifteen years later, the emperor Valens (r. 364–378) would face a similar fate at the battle of Adrianople.

At about the same time as the Romans were battling the Persians in Mesopotamia, another threat was emerging in the east. Nomads from the Eurasian steppe known as Huns moved into eastern Europe, putting pressure on the semi-nomadic Germanic tribes massing against the Roman Limes (Map 5.5). One of these tribes, the Visigoths (western Goths), sought Valens’ permission to cross the Danube and settle in Roman territory. The emperor agreed to the migration if the Visigoths gave up their arms and settled in Thrace as farmers. In late 376 the Visigoths crossed the Danube (perhaps 200,000 strong, including men, women and children) but were exploited by Roman officials. By 378 impending starvation forced the Visigoths to ravage Thrace and besiege the city of Adrianople (modern Edirne, Turkey), where they had been resisted and denied food by local authorities.

To meet this threat, Emperor Valens assembled an army and marched north from Constantinople to meet the barbarians. At Adrianople, Valens waited for the arrival of the Western Roman emperor, Gratian. But, believing the Goths only had 10,000 men under arms, Valens decided to attack immediately and seize all of the glory for himself. On 9 August the Roman emperor left the city at the head of an army of between 15,000 and 20,000 troops.

Eight miles out of Adrianople, Valens’ column surprised a Gothic wagon laager formed in a defensive circle on a low hill, containing an army comparable in size to the Roman host (the proportion of infantry to cavalry is unknown for either army). Valens deployed his infantry behind a screen provided by his right wing cavalry and light infantry archers. As the Romans were deploying from column, the Visigothic leader Fridigern ordered the grasslands set on fire. In response, Valens ordered his skirmishers to attack in order to buy time as his column deployed.

The Barbarian Invasions.

But the Roman skirmishers, light infantry archers (sagittarii) and elite cavalry (scutarii) from the emperor’s bodyguard, committed themselves too strongly to the effort. Instead of performing the traditional role of light troops (harassing enemy formations, then retiring behind their own infantry), the Roman skirmishers engaged with the Visigoths. The Visigothic counter-attack threw the Roman skirmishers into their own infantry lines, disrupting the Roman centre. At that moment, the Gothic cavalry returned from foraging and attacked the Roman right flank and drove off the Roman cavalry. The Roman line finally gave way, but not without spirited fighting. Seeing the Roman centre in disarray, the Goths sallied out of their wagon circle and attacked the Roman centre as additional Gothic cavalry struck the Roman left, driving off the Roman cavalry. Outflanked by barbarian cavalry and encircled by enemy infantry, the Roman foot soldiers were pushed into a mass of bodies so compacted that they were unable to wield their swords properly. Perhaps two-thirds of the trapped Roman army was killed, including Emperor Valens; his body was never recovered. The contemporary historian Ammianus tells us that it was the worst Roman defeat since Cannae.

Though cavalry was present on both sides, the Gothic victory over the Romans at Adrianople was essentially one of infantry over infantry. This fact is significant in itself in that the Roman army was unable to defeat a barbarian army only slightly larger, when in centuries past it had regularly defeated enemy hosts many times its own size. No doubt the Roman army’s abandonment of the close-order drill utilizing gladius, rectangular scutum and body protection which had served them so well during the Pax Romana contributed to this debacle, depriving the soldiers of a significant advantage over their enemies. And though Gothic infantry carried the day, the barbarians’ use of cavalry as a part of a combined-arms attack also was a harbinger for the role cavalry would play in later Byzantine warfare in a way reminiscent of Alexander or Hannibal. The superior Gothic horse, by defeating their Roman counterparts, turned the tide of the battle by hemming in the Roman foot soldiers, allowing for the massacre of over 10,000 Roman veterans.

After the battle of Adrianople, Rome agreed to allow the victorious Visigoths to settle in the Roman Empire. In return, the Visigoths promised to fight for the empire as allies or foederati. As such they retained their Germanic commanders and were allowed to roam within the boundaries of the empire. But by virtue of their strength they soon capitalized on the weakness of their Roman hosts, and began marauding throughout the Balkan peninsula. The very same Visigothic tribe that crossed the Danube in 376 seeking refuge from the Huns sacked Rome in 410, something that had not been done since the Celts took the city some 800 years before. Even with the assistance of foederati, the Roman military was unable to hold back the invading Germanic and central Asian tribes. By the first decades of the fifth century, the barbarians were regularly crossing the frontiers into Roman territory.

Perhaps the most infamous of these tribes, the Huns, were united under a charismatic and brutal chieftain named Attila (d. 452), who regularly terrorized the Danubian frontier and the Eastern Roman Empire, exacting a large tribute from the emperor Theodosius II. When Theodosius’ successor refused to pay tribute in 450, Attila suddenly shifted his attention to the west, leading his Hunnic confederation across the Rhine and into Roman Gaul. But the army of the Huns had changed since the nomads first appeared from the Eurasian steppes in the mid-fourth century. The Hunnic army then was predominately cavalry, relying on a mix of light cavalry horse archers and heavy cavalry lancers reminiscent of the Parthians. When the Huns moved out of the Eurasian steppes and entered the Hungarian plain, they lost the ability to support their large mounted army logistically.

To adapt to the forests of central and western Europe, the Huns adopted the panoplies and infantry tactics of the Germanic tribes they assimilated into their confederation. The army Attila the Hun commanded would have more in common with the Visigoths and Romans than with the steppe nomads. Like the Germans and ‘barbarized’ Romans, the Hunnic infantryman wore no armour, at least no breastplate or helmet. Hunnic and Germanic nobles probably wore helmets, but mail armour was very uncommon. Unencumbered by heavy armour, barbarian infantry was light and mobile. When the Huns crossed the Rhine in 451, they faced a Roman army with similar characteristics.

The commander of the western Roman army in Gaul, Flavius Aetius (c.395–454), was a product of the new barbarization of the imperial army. Born of a Scythian father and Italian mother, Aetius rose through the ranks of the Roman army as a cavalry commander, becoming the most capable general the late Western Roman Empire produced and the de facto ruler of Gaul. Aetius’ relationship with the Huns was not always antagonistic. The Roman general persuaded the Huns to attack the Burgundian foederati marauding along the lower Rhine, wiping out 20,000 of the invaders. But Aetius’ influence over Attila had waned by the late 440s, and the ‘Scourge of God’, as Attila was known to Christianized Europe, turned his attention toward the Western Roman Empire. Early in 451 Attila invaded the Rhine, supported by a large army of Huns and associated allies such as the Ostrogoths, Burgundians and Alans. This Hunnic confederation crossed the Rhine on a broad front stretching from Belgium to Metz and brought the city of Orleans in central Gaul under siege.

To meet this Hunnic confederation, Aetius allied himself with the Visigothic king, Theodoric I – son of the infamous Germanic ruler Alaric II, who sacked Rome in 410. The combined armies marched to the relief of Orleans. The Huns, unwilling to be caught between the walls of Orleans and a relieving army, abandoned the siege and withdrew northward. Here, a large battle developed near the city of Châlons on the Catalaunian plain in what is now the Champagne district of France. Known to history as either the battle of Châlons or the Catalaunian Plains, the engagement ‘was one of the decisive encounters in the history of the western world’.

On 20 June, the day of the battle, Attila was uncertain of victory. He maintained his forces behind a wagon laager until late in the day, presumably to delay the battle in order to use the cover of darkness for escape in case the battle went poorly. When Attila finally offered battle, he placed himself in command of his most reliable troops, the Huns, arraying them in the centre of the line in order to push through the enemy’s centre. The Hun commander then placed the Ostrogoths on his left wing, and his other allies on the right.

Aetius decided on an opposite strategy. The Roman commander placed his least reliable troops, the Alans, in the centre to take whatever attack Attila might launch, then arrayed his Visigoths on his right and his Romans and Franks on the left wings to execute a double envelopment on the flanks of the enemy. Like Adrianople seven decades earlier, the battle that would take place would be primarily an infantry rather than a cavalry engagement. Contemporary sources do not give us a reliable estimate of the belligerents’ troop strengths, but an estimate of perhaps 25,000 to 30,000 troops on each side is not out of the question.

The initial skirmish took place on Aetius’ left, where the Romans seized the high ground, giving them the advantage for a planned flanking manoeuvre. When battle was finally joined, the Huns struck hard against the Alans in Aetius’ centre, pushing the foederati back. Attila then wheeled to hit the Visigoths in the flank. In heavy fighting, King Theodoric was killed, but his Visigoths rallied and counter-attacked. Meanwhile, the Romans and Franks threatened Attila’s weak right flank from their superior position on high ground. Witnessing a counter-attack on his left and the threat of envelopment on his right side, Attila called for a retreat to the wagon laager as Hunnic archers kept the Romans and Germans at bay (Map 5.7(b)). Under the cover of darkness, the Huns slipped away from the battlefield. Casualties on both sides were horrific, but in the end, the victory was Aetius’. Attila was forced to retreat beyond the Rhine.

The Roman victory at Châlons was a near-run thing, and the narrow margin of victory suggests parity in forces, both quantitatively and qualitatively. Aetius and Attila met on the battlefield with relative equality in numbers. It is not known for certain what role cavalry played in this engagement, but one can surmise that horsemen were present on the battlefield, though not in large numbers. The Hunnic confederation suffered great losses, enough to abandon the fight and withdrawal from Gaul. And while Aetius won the day, his forces suffered heavy casualties, including the loss of King Theodoric.

By the middle of the fifth century, the equipment and tactics of the Huns, Germans and Romans were very similar. Aetius’ confederation of Romans and barbarians was essentially a mirror image of Attila’s forces: poorly armed and armoured unarticulated infantry fighting with limited cavalry support. The battles of Adrianople and Châlons illustrated the decline of the Roman heavy infantry. Gone were the days of a Roman legion meeting and defeating a barbarian army three times its size.

Aetius’ victory over Attila at Châlons did not end the Huns’ threat to the Western Roman Empire. In 452 Attila crossed the Alps and pushed into Italy with a vengeance. The city of Aquileia was utterly destroyed, while Milan, Verona and Pavia were either bankrupted bribing the Huns or depopulated. The city of Rome was saved only by papal intervention. But western civilization was spared further deprivations when Attila asphyxiated on his wedding night, and the Hunnic confederation, without a strong personality to lead it, dissolved.

With the Huns gone, the power vacuum in western Europe was filled by a combination of foederati already present within the borders of the Western Roman Empire or new tribes crossing the frontiers. No longer willing to live under the pretence of Roman hegemony, these barbarians carved up the Western Roman Empire into their own Germanic kingdoms. By 476 the last Roman emperor in the west, Romulus Augustulus, would simply be removed by a Germanic army commander, Odovacer, ending a millennium of Roman control in central Italy.

With the fall of the Western Roman Empire came the disintegration of the political and economic infrastructure needed to field a professional army. By the time the end came, centuries of ‘barbarization’ had eroded the combat efficiency of the Roman legion, and with the end of the professional army came the end of well-articulated heavy infantry, replaced by the Germanic militia system and its unarticulated battle squares. Though articulated heavy infantry would continue to exist in the Byzantine east with a greater reliance on cavalry, in western Europe the tactical dark ages had arrived.