Rome at War
1706581112 197 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.

1706581112 907 Rome at War

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.

1706581112 995 Rome at War

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.

1706581112 823 Rome at War

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.

1706581112 908 Rome at War

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.

1706581112 934 Rome at War

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.

1706581112 295 Rome at War

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.

1706581112 278 Rome at War

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.

1706581112 736 Rome at War

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.

1706581113 642 Rome at War

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.

1706581113 760 Rome at War
1706581113 225 Rome at War

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).

1706581113 56 Rome at War

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.

1706581113 317 Rome at War

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.

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