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PROOF
Historia
Zeitschrift für Alte Geschichte
Revue d’Histoire Ancienne
Journal of Ancient History
Rivista di Storia Antica
Historia Band xx • Heft x • 201x
© Franz Steiner Verlag, Stuttgart
ROMAN INFANTRY TACTICS IN THE MID-REPUBLIC:
A REASSESSMENT
Abstract: This article explores two questions about the tactical mechanics of the Roman manipular
legion. First, what frontages did the Roman legion field in set-piece battle? Given that Hellenistic
forces deployed in standardized formations, the length of Hellenistic infantry lines can be used to
calculate the opposing Roman formation. This in turn permits consideration of the nature and tactical
function of the gaps between the maniples. The paper deduces that Roman legions presented fronts
between 320 and 570 meters in five set-piece battles. The range of frontages suggests that modest
inter-manipular gaps were maintained even as the heavy infantry lines clashed.
This article offers a reassessment of an old topic: legionary infantry tactics during the age
of Roman expansion, in particular the manipular tactics that predominated between the
3rd and 1st centuries BC.1 Despite a keen scholarly interest in Republican tactics dating
back to the age of Machiavelli, basic questions still remain concerning Roman tactical
dispositions. Students of the Roman army are familiar with one of the most famous (and
traditionally fruitless) tactical controversies concerning the manipular legion: did the
Romans leave gaps between the maniples in combat, or were they closed by some obscure
mechanism?2 A still more fundamental question has never been answered satisfactorily:
what was the frontage, or possible frontages, of a legion, and to what extent was that
1
2
I would like to thank Carlos Noreña, Tom Hendrickson and Laura Pfuntner for reading and commenting on early versions of this article. Thanks also to Timothy Winters and Christos Kollias, who took
an American School bus on a long detour to allow me to inspect the battlefield at Cynoscephalae.
The anonymous readers at Historia provided valuable feedback and criticism that led to a vastly
improved article. Most of all, my gratitude to my wife Kelsey Mayo and to our little Caroline, for
their love and support.
A clunky mechanism of laterally counter-marching the rear century to plug the gap is favored by Connolly, 1998: 141–142 followed by Daly, 2002: 61–62 et alii, but such a maneuver seems excessively
difficult to execute under combat conditions. Soltau, 1885: 265–267 and Quesada-Sanz, 2005:7–8
propose having maniples expand laterally into the gaps, with soldiers in the process expanding their
frontage from three feet to six feet. This maneuver might be feasible during a lull in combat, but
still seems clumsy and time consuming. Delbrück, 1920 {1975}: 273 argues that the intervals were
extremely small (more joints than gaps), and were closed automatically as men in the rear ranks
pressed forward into them once enemy contact was made. Any large gap was sealed by the timely
advance of a century from the principes or triarii.
2
Michael J. Taylor
frontage potentially extended by inter-manipular gaps?3 Answering these questions will
greatly illuminate the dynamics of the mid-Republican legion in battle.
Tactical analysis is one facet of ancient military history that has been out of fashion for well over a century, after significant interest in German scholarly circles prior
to World War I.4 When Frank Adcock delivered his Martins’ Lectures on The Roman
Art of War in 1939, the influence of German scholarship on manipular tactics had been
waning for nearly a generation, and Adcock did not dwell on the question of Manipulartaktik. Since the 1960s, military history, both ancient and otherwise, has fallen mostly
into two schools. The first school, sometimes known as the “New Military History,”
focuses on the social, political, demographic and economic factors related to warfare,
tackling everything from the social makeup of armies and officer corps to the cultural
impacts of military violence.5 While New Military History has provided many insights,
it has one primary drawback: it generally ignores or downplays acts of combat, the
very reason why societies muster military forces in the first place. Beginning with the
late John Keegan’s 1978 book, Face of Battle, a military-historical school of thought
bearing the same name has arisen, focusing on the mechanics of combat at the level
of front-line soldiers. Philip Sabin has applied this approach to the Republican Roman
legion in his 2000 article “The Face of Roman Battle.”6 The two schools of thought
have some overlap. Victor Davis Hanson strongly linked the hoplite “face of battle” to
the social and cultural world of the Archaic and Classical polis, while Jon Lendon has
recently discussed ancient combat in relation to cultural dynamics, stressing that classical soldiers were motivated by an aggressive and heroic ethos, which was reflected
in their tactical dispositions.7
3
4
5
6
7
Lendon, 2005: 181–182. Frontages for reconstructed legions vary wildly. Bar Kochba, 1979: 166
suggests each legion at Magnesia had a frontage of 450 meters. Sekunda, 1996: 19 puts the standard
frontage of a 4200-man mid-Republican legion at 800 yards (720 meters). Goldsworthy, 1996: 140
suggests that a cohort-based legion could have a frontage of over 1125 meters. Bahmanyar, 2009:
54 estimates legionary frontages of 800–1200 m. I have earlier suggested in a popular publication
(Taylor, 2011:12) a range of frontages from 400–850 yards (360–765 meters), although the uncertainty led me to reevaluate the problem more closely.
The primary benchmarks of late 19th-early 20th century German tradition are Delbrück, 1883, Soltau,
1885, and Schneider, 1893 and the immense corpus of Kromayer and Veith (e. g. Kroymayer, 1905;
Kromayer and Veith, 1907). By the time Delbrück published his magisterial Geschichte der Kriegskunst in Rahmen der politischen Geschichte, intractable controversies remained over the frontage
of each soldier (three feet vs. six feet), and the size and purpose of intervals. The diminishing returns
in resolving these controversies caused the topic of manipular tactics to be largely abandoned by
serious scholarship ever since.
For an overview of “New Military History,” see Paret, 1991 and Morillo and Pavkovic, 2006: 37–43.
Webster, 1969 and Keppie, 1981 represent the application of New Military History to the Roman
army. For a rollicking critique of the current state of ancient military history, see Wheeler, 2011:
54–104.
Wheeler, 2001: 169–174 offers a critique of the “Face of Battle” methodology as applied to ancient
military studies.
Hanson, 1989: passim, Lendon, 2005: 163–211.
Roman Infantry Tactics in the Mid-Republic: A Reassessment
3
Both schools of military history either ignore or minimize the role of tactics. The
topic of mid-Republican tactics, however, is not merely an obscure technical question,
but rather one that lies at the heart of one of the great problems in Roman history: the
need to explain Rome’s rise to pan-Mediterranean dominance in the 3rd and 2nd centuries
BC. Unlike European colonial empires from the 16th century onward, which were established on the basis of overwhelming technological, economic and military superiority,
Rome’s Hellenistic opponents (Carthage included) possessed well-organized military
institutions, backed by sophisticated state economies. Perhaps most importantly, all
Roman warfare was conducted on the basis of basic technological parity, with all sides
fielding an iron-age arsenal of spears, swords and shields, albeit with varying designs.
Despite this organizational, economic and technological symmetry, the Roman army
was able to triumph repeatedly over formidable rivals in a series of critical wars that
would reshape the international dynamic of the Mediterranean basin. While the warfare
of the period was often characterized by long and grinding campaigns, as well as plenty
of Roman setbacks, it was punctuated by a set of unusually decisive Roman victories
in set-piece battles (e. g. Ilipa, Zama, Cynoscephalae, Magnesia and Pydna), where the
outcome of entire war hinged upon a single day of fighting. The Roman army’s ability
to defeat and substantially destroy opposing forces ultimately proved the indispensable
prerequisite of Roman expansionism. An examination of the Roman army in its tactical
array is therefore central to understanding how this ancient institution shaped the arc of
Mediterranean political history.
In exploring mid-Republican tactics, this essay will build conclusions progressing
in scope from the level of the individual soldier to the entire legion. First, I propose a
hypothesis concerning the space required by Roman soldiers in formation, based on a
reassessment of Polybius 18.30, and offer a model for the transition of Roman infantry
formations between a defensive close order formation and an offensive open order.
Next, I examine five battles fought between Roman and Hellenistic armies. Given that
Hellenistic armies utilized doctrinal tactics that are well documented by Polybius and
later Hellenistic tactical writers, it is possible to reconstruct Hellenistic battle lines,
and in turn to re-imagine opposing Roman infantry frontages. By calculating a range
of potential maniple frontages, I note how much of the legionary frontage potentially
consisted of the space devoted to inter-manipular gaps. I conclude with a brief discussion
of the importance of inter-manipular gaps to the success of the legion on the battlefield.
Literary Sources and Roman Tactical Practice
The most reliable source for the mid-Republican army is the contemporary eyewitness
Polybius, present in Rome from 167 BC onwards.8 Polybius saw the Roman army in
action on multiple occasions; he collaborated with the Roman campaign against Perseus
8
The literature on Polybius is extensive; I have been largely informed by Walbank, 1990, Eckstein,
1995, Champion, 2004, consulting throughout the commentary in Walbank, 1957.
4
Michael J. Taylor
and was present as an observer at the siege of Carthage in 146 BC.9 In addition, Polybius interviewed veterans of major pitched battles, in particular Gaius Laelius (Scipio
Africanus’ chief lieutenant during numerous battles of the 2nd Punic War) and his friend
and patron Scipio Aemilianus, who fought as a young man at Pydna.10 Polybius also
consulted contemporary military literature: Elizabeth Rawson has argued that he utilized
a sort of “field manual” for military tribunes in his composition of Book 6.11
Livy, writing over a century later, was entirely dependent on earlier sources, including many now-lost passages of Polybius as well as other late-annalistic historians
of mixed value.12 Nonetheless, while doubts will always persist about the accuracy of
Livy and his even more chronologically removed imperial successors, we do know
that these later historians had access to a number of now-lost high quality sources on
military affairs from the mid-Republic, including Cato the Elder’s de re militari, Scipio
Africanus’ letter to Philip V which described
his actions during the 2nd Punic War, and Scipio Nasica’s eyewitness account of the
battle of Pydna.13
The Tactical Space of Roman Soldiers
Scholarly work in the last decade has produced a new model of combat mechanics within
the Roman Republican legion. While the individual scholars who have made important
contributions to the problem (most notably Adrian Goldsworthy, Philip Sabin, Michael
Zhmodikov, Jon Lendon and Fernando Quesada-Sanz) do not agree on all details, a
basic consensus has developed. The Roman maniple was not a closely packed, rigid
18th century-style formation, but rather a looser formation that gave individual soldiers
significant leeway to break ranks in order to, in the words of the mid-Republican military
oath, “retrieve a missile, to pursue and strike an enemy or save a fellow citizen” teli
sumendi aut petendi et aut hostis feriendi aut ciuis seruandi causa.14
Nonetheless, it is safe to assume that before the Roman legion engaged in its fluid
style of combat, men were arranged in orderly, roughly rectangular formations. A maniple was not a mob. For example, Polybius reports the Romans arrayed for battle against
the Gauls in 222 BC with “the tribunes demonstrating to each and all how they should
enter battle, both as units and as individual fighters”
9 Polybius as a collaborator in the 3rd Macedonian War: 28.13. Eyewitness to the 3rd Punic War: 38.19;
Ammianus Marcellinus 24.2.16. Eckstein, 1995: 280.
10 Gaius Laelius as an informant: Polybius 10.31. Polybius’ close friendship with Scipio Aemilianus:
31.23–25. Aemilianus at Pydna: Plutarch, Life of Aemilius, 22.3–8.
11 Rawson, 1971: 15, 20. Note also the centrality of the tribunes at Pol. 2.33.1.
12 On the formulaic battle narratives in late annalistic historians, see Erdkamp, 2006.
13 Scipio Africanus’ letter to Philip: Polybius 10.9.3; Cato’s de re militari: Vegetius 1.8, 1.13, 1.15,
2.3, Frontinus Strat. 3.1.16. Scipio Nasica’s account of Pydna: Polybius 29.14.3, Plutarch Aemilius
18.5. On mid-Republican military memoirs: Canadu, 2011: 122–133.
14 Livy 22.38.4; Lendon, 2005: 179, Quesada-Sanz, 2005: 7. Phang, 2008: 49–60.
5
Roman Infantry Tactics in the Mid-Republic: A Reassessment
›
.15 Thus, while maniples in
combat might subsequently bunch up or stretch out in the inevitable chaos of combat,
it is possible to consider the pre-combat arrangement of soldiers, and the depths and
frontages of their maniples.
Polybius describes the Roman infantry dispositions as follows (18.30.6–8):
·
›
›
,
,
›
,
›
,
.
Each Roman with his equipment also occupies three feet. But in their manner of
fighting each man undertakes movement on his own, protecting his body with his
long shield, parrying a blow, and fighting hand to hand with the cut and thrust of his
sword. They therefore clearly require a space and flexibility between each other, so
that each soldier must have three feet from the man to their flank and rear, if they
are to be effective.
Here it is important to differentiate between “tactical space,” the total amount of space
a soldier has before bumping into his comrades on the left and right, and “file width,”
the amount of space a soldier has from the right shoulder of the man on his left to his
own right shoulder. This passage is usually interpreted to suggest that the file width
of each Roman soldier was six feet (1.8 meters): the three feet the soldier physically
occupies plus the three-foot gap to the man on his right and another three feet to the
left.16 This would give the Roman soldier a tactical space of nine feet. Such spacing is
undeniably too generous, as it would leave the Roman infantryman painfully exposed
while dramatically reducing the weapons density of the front line.17 However, this does
not mean the passage should be ignored in favor of the spacing indicated by Vegetius
(3.14), who assigns a mere three feet to each Roman soldier. From a source criticism
perspective, to prefer the Late Imperial Vegetius over the contemporary Polybius is a
dubious choice.18 More materially, Vegetius’ spacing simply does not provide sufficient
room to fight.
15
16
17
18
Polybius 2.33.1.
E. g. Walbank, 1957: 588–589.
Delbrück, 1975 {1920}: 406–410, Daly, 2002: 160, Goldsworthy, 1996: 171.
It should also be noted that while Vegetius 3.14–15 makes reference to hastati and principes, none
of the formations he describes bears any resemblance to mid-Republican tactics: he reports formations of up to 10,000 men arrayed into huge blocks, and makes no mention of maniples, the triplex
acies or legions and alae. I do not believe it is correct to assume that this section utilizes a Republican source (pace, Goldsworthy, 1996: 179). More likely this passage represents a typical Vegetian
amalgam of sources and historic periods, a hypothetical exercise that is unrelated to any historical
tactical disposition.
6
Michael J. Taylor
The Roman soldier required significant space to wield his sword, if only to prevent
him from accidentally slicing the comrade next to him. Archaeological developments in
Spain over the last fifteen years have identified the gladius hispaniensis, and revealed
that it was in fact quite long for an ancient infantry sword.19 Average blade length, not
counting the tang, was 65 centimeters (25 inches), substantially longer than Greek and
Macedonian blades.20 The length of blade confirms testimony in both Polybius and Livy
that indicates the essential slashing function of the sword.21 Slashing motions with a
62–69 cm blade would have required an open spacing, whereas Vegetius’s spacing of
three feet would facilitate only cramped and ineffective stabbing motions.22
It seems that the correct reading of Polybius refers to a tactical space of six feet,
rather than a file width, with the former defined as the space between a soldier’s comrades
on the right and left, and the latter being the space each soldier occupied calculated
from right shoulder to right shoulder.23 Polybius does not distinguish between the two,
partly because in his discussion of Macedonian soldiers in close order, file width and
tactical space are identical. The Macedonian only has the space he physically occupies
along with his arms and equipment, and brushes up against the men on either side.24
The Roman soldier has double the tactical space of a Macedonian soldier, some six feet
to operate in compared to three feet, but the actual “file width,” from right shoulder to
right shoulder, would in fact be four and a half feet per soldier, given that some of the
six feet of frontage is shared between adjacent soldiers.25 This is a plausible space in
which to engage in vigorous swordplay, but not so wide as to make individual Roman
soldiers excessively spaced and isolated on the battlefield.
A 4.5 foot file width would have been quite easy for soldiers themselves to measure. Modern soldiers in the US Army conducting drill and ceremony obtain a “Normal
Interval” of just under 4.5 feet simply by holding out their right arm until they touch
the left shoulder of the soldier next to them, and this expedient was available to their
ancient counterparts.26 Indeed, this sort of measurement may be exactly what Polybius
19 Quesada-Sanz, 1997: 256; 2005: 6. Bishop and Coulston, 2006: 55–56.
20 Snodgrass, 1967: 84–85, 119, illustrations no. 50–52. Greek swords generally have a total length of
just under 55 cm, with blades of around 45 cm, reflecting their use as secondary weapons in compact
formations.
21 Bishop and Coulston, 2006: 56. The Pydna monument at the Delphi museum (c. 160) depicts a Roman soldier making a broad overhead slashing movement with his sword.
22 Gladius hispaniensis: Quesada-Sanz, 2005: 6. Kromayer, 1905: 11–13 vigorously argues that three
feet was insufficient spacing, part of an ongoing, and often testy, exchange with Hans Delbrück.
23 Sage, 2008: 85–86 argues that Polybius’ six feet should be read from the left shoulder of the soldier
on his right to the right shoulder of the soldier on his left, and suggests a roughly two foot interval
between soldiers.
24 Polybius 18.29.1–5.
25 Polybius states that the Roman soldier occupies a physical three feet of space (for shield, and the
part of the body not covered by the shield), in the center of his six feet of frontage. This implies 1.5
feet of empty space on either side, for a file width of 4.5 feet. Throughout I will convert a foot to .3
meters, admitting that it is unclear which ancient foot Polybius is using.
26 US Army Training Circular (TC) 3.21.5 (Drill and Ceremonies), Figure 6.2.
Roman Infantry Tactics in the Mid-Republic: A Reassessment
7
has in mind when he describes
…
, as a Greek would
measure three feet (a half orguia) from the fingertips of his outstretched arm to his nose,
so that Polybius’ “three feet on either side” (six feet, a full orguia) would include the
space the soldier himself physically occupies.27
A Roman soldier’s shield ultimately defined the dimensions of his tactical space,
and here it is perhaps no coincidence that a Roman scutum was just over two feet wide,
or approximately half a file-width. Polybius (6.23.4) reports that the Roman scutum was
2.5 feet (.75 m) lengthwise, although this likely refers to the span of the convex face of
the shield, making the actual width c. 65–70cm.28 Our only surviving Republican-era
shield, found in the Fayum at Kasr el-Harit, and dating to the Late Republic, has a width
of .635m.29 Roman shield widths would have varied, given that Roman militiamen supplied their own equipment. Nonetheless, the Romans did seem to have a general sense
of a “standard” shield, so that Scipio Aemilianus could admonish a soldier for having
amplius eum scutum iusto ferre.30
We therefore have a simple mechanism by which Roman soldiers measured their
own frontage: in the early phases of battle, characterized by missile exchange, soldiers
adopted a close order formation with shields touching or nearly touching. As the battle
moved into a phase of hand-to-hand combat, the formation opened by flexing forward,
so that every legionary had a file width roughly double a shield-width, approximately
4.5 feet (1.35m), the figure used in my calculations.
Close Order and Open Order Formations
Several passages describe the transition from close order formations to open ones: Livy
(28.2.7–9) describes a shower of Celtiberian javelins during the 2nd Punic War which
“the Romans, closing together according to custom, received with their shield wall”
romani conferti, ut solent, densatis excepissent scutis. Once they had received the missile
barrage and began to advance over rough terrain, the Romans flexed into a more open
formation, so that “they opened their ranks and clashed singly or in pairs, resembling
matched gladiators” ordines dirimebant et singuli binique uelut cum paribus conserere
pugnam cogebantur.
27 An orguia is prominently featured on the Salamis Metrological Relief, on display in the Piraeus
Archaeological Museum; Dekoulakou-Sideris, 1990: 446–447.
28 Treloar, 1971: 5.
29 Kimmig, 1940, although the shield is identified incorrectly as Celtic. This shield may be a Roman
model used by Ptolemaic soldiers (or Roman mercenaries in Ptolemaic service). An early imperial
auxiliary shield from Doncaster, while differing in construction from a Republican scutum, also has
a width of .64 m (Buckland, 1978: 256), almost identical to the Fayum scutum. Both Polybius and
the Fayum scutum are similar to the images of Republican scuta on the Pydna monument and the
Louvre “Ahenobarbus” Relief. See also Sekunda, 2006: 80–83, who emphasizes the Fayum shield
is of Roman design.
30 Livy Per. 57.
8
Michael J. Taylor
Surrounded by Macedonian skirmishers during the 3rd Macedonian War, the commanding tribune of a Roman foraging party “formed the soldiers into a circle, so that
they might defend themselves with a shield wall from the hail of arrows and darts” in
orbem milites coegisset, ut densatis scutis ab ictu sagittarum et iaculorum sese tuerentur – note the repetition of the phrase densatis scutis. In this initial defensive formation,
the soldiers lacked sufficient space to effectively wield their weapons. They eventually
attempted to open their ranks by flexing forward: ordines procursando soluissent.31 We
see a similar trend in an urban environment: during the siege of Sparta in 195 BC, Roman soldiers formed a close order testudo in response to missile fire.32 However, they
soon sought tactical space to wield their weapons, taking advantage of a patentiorem
uiam to transition to the offensive.33
The need for Roman soldiers to lock shields when on the defensive, particularly
in response to missile threats, may also explain one of the most puzzling passages in
Polybius, one commonly bracketed as corrupt. Polybius (15.13.1) reports that the Roman hastati fought at Zama “using neither spears nor swords”
.34 What Polybius may in fact describe is the Romans’ close order formation
in response to the missile threat coming from Hannibal’s Balearic slingers and other
light infantry in the Carthaginian first line. However, the hastati then struggled to flex
forward out of their defensive formation to obtain the space they needed to effectively
wield their swords in an open order, and so the fighting for a while involved Romans in
close order shoving forward with their shoulders against interlocked shields.35
Transition to an open order formation may have been as simple as every other man
in the front ranks stepping forward until they achieved appropriate intervals. (Likewise,
closing the ranks might involve soldiers in alternating rear ranks stepping forward
between the two men in front).36 If this maneuver were conducted by files, the entire
formation would double its depth as it transitioned into open order, although in the press
of combat it is possible that only the first few ranks would do so. A fluid open order
31 Livy 42.65.7–9, Zhmodikov, 2000: 74.
32 Livy 34.39.6–8.
33 Cf. Caesar, BG 2.25.2 for a transition into the offensive: manipulos laxare iussit, quo facilius gladiis
uti possent and Tacitus, Hist. 3.17 for a defensive formation densis ordinibus.
34 For an overview of criticism of the passage and various interpretations, see Walbank, 1957: 459. Livy
seems to have read the passage and interpreted that the Romans fought “striking with shoulders and
shield bosses” ala deinde et umbonibus pulsantes. Polybius is no doubt in error if he characterizes
all hand-to-hand fighting during the battle in this manner. The heavy casualties the Romans inflicted
on the first two lines of Carthaginians suggests that they did indeed find sufficient tactical space to
wield their weapons with deadly effect.
35 For a similar case of close order othismos with locked shields, see Livy 34.46.10–11, as Roman
soldiers struggled to egress out of a narrow gate, and were for a while unable to open their formation.
36 Sabin, 2001: 10, Daly, 2002: 61 and Judson, 1888: 43, although all suggest movement from a three
foot spacing to a six foot spacing. Cf. US Army TC 3.21.5, (Drill and Ceremonies) Paragraph 7–7,
“Opening and Closing Ranks,” for a similar maneuver used by modern troops on parade.
Roman Infantry Tactics in the Mid-Republic: A Reassessment
9
could also be achieved in melee combat with the most daring soldiers dashing forward
to form a loose skirmish line, still the preferred technique of Pompeian troops in Spain
during the Late Republic.37 In both cases, the frontage of the maniple remained the
width of the original close order shield wall.
Number of Ranks in Roman Formations
Cato the Elder writes in his de re militari (Jordan 9.1) that pedites quattuor agminibus
equites duobus antibus ducas. The quattuor agmines may well be the four columns of
velites, hastati, principes and triarii, although the pairing with the term antes (a word
also applied to rows of vines) implies ranks of soldiers within a formation. If so, Cato
may envision a tactical system based on files of 4/8 in close/open order.38 Livy (44.9.6)
reports a testudo four-men deep in 169 BC. It is not impossible that the four man guard
details (
o ) described by Polybius (6.33.7) correspond to a close-order file.
Looking beyond the mid-Republic, data concerning the depth of Roman soldiers in formation in is rare, scattered chronologically, and from sources of varying quality. Table 1
collects references spanning from the mid-Republic into the Late Empire:
Table 1: Depth of Roman Soldiers in Formation
Source
Depth
Formation Type
Republican Period
Cato, de re militari
4
Unknown
Livy 44.9.6
4
Testudo
Frontinus 2.3.22
10
Combat
Plutarch, Antony 45.2
3
Testudo
Imperial Period
Josephus BJ 2.172
3
Riot Control Cordon
Josephus BJ 5.131
3
Defensive perimeter
Josephus BJ 3.124
6
Marching column
Trajan’s Column
4
Testudo
Arrian Ectaxis, 16–17
8
phalanx
Column of M. Aurelius
3
Testudo
Vegetius 1.26
4
Training drill
Vegetius 3.14–15
3,6,9
Combat
Date of Action
n/a
169 BC
48 BC
36 BC
26–36 AD
70 AD
60s AD
100s AD39
135 AD
170s AD40
n/a
n/a
37 Caesar, BC, 1.44.1–2: Genus erat pugnae militum illorum, ut magno impetu primo procurrerent, audacter locum caperent, ordines suos non magno opere servarent, rari dispersique pugnarent. Kromayer,
1905: 15–17 proposes a similar method of developing a battle line out of a close order formation.
38 Wheeler, 2004: 160. Wheeler suggests that Cato himself may be reliant on a Greek tactica, possibly
by none other than Polybius.
39 Photo in Settis et al., 1988: 376.
40 Photo in Coarelli, 2008: 220–221.
10
Michael J. Taylor
While the evidence is hardly conclusive, close order formations three or four men deep
appear with the greatest frequency, which would then presumably transition into open
order formations six or eight deep. The deepest attested (open order?) formation is
Pompey’s ten ranks at Pharsalus (Frontinus 2.3.22), although Polybius reports unusually
deep mid-Republican formations at Tunis and particularly at Cannae, where the depth
of maniples is said to be many times the width of their front.41
In the next section I will attempt to ascertain the size of legionary frontages, and
from this deduce the width of inter-manipular gaps necessary to maintain those formations. Given the uncertainty regarding the exact depth of maniples in any engagement,
I will calculate maniple frontage based on a range of possibilities, namely formations
in close/open order 3/6 deep, 4/8 deep, 5/10 deep, and so on (see Table 2). Fortunately,
it will not be necessary to plug in endless variables, as a point will quickly arrive where
the maniples could not be made deeper without making the inter-manipular gaps larger
than the frontage of the maniple itself. I will, however, exclude formation depths of
one and two ranks deep in close order, which are not attested in any historical source.42
Such formations would be too shallow to be tactically effective, as the death of a few
soldiers would quickly dissolve the integrity of the entire line.
Case Studies
To determine the overall frontage of a Roman legion, I will examine Roman dispositions
in battle against Hellenistic enemies whose strength and tactical disposition are relatively
well attested in ancient sources. This project supposes that Roman commanders actively
attempted to match the frontage of the opposing force.43 All ancient armies had reason
to be concerned that the opposing infantry line would extend its wings and turn one
or both flanks. The Athenians and their allies at Nemea in 394 BC engaged in lengthy
counsels to determine the appropriate depth of their forces to ensure that their line was
of sufficient length to prevent a Spartan envelopment.44 Caesar, badly outnumbered
while fighting in Africa, was forced to extend his line into a simplex acies when faced
41 Polybius reports that the legions at Tunis in 255 BC were formed
,
(1.33.10), while at Cannae in 216 the maniples were
,
(1.113.3–4).
42 The only reference to ancient formations two men deep come from a fantastic passage in Xenophon,
describing a battle between Persians arrayed two deep, and Egyptians arrayed 100 deep, which
should not be taken for evidence of a historical formation (Xenophon, Cyropaedia, 6.3.21–7.1.34;
see Wheeler in Sabin et al., 2007: 210).
43 On the symmetry between opposing armies in the ancient world, see Sabin et al., 2007: 405. N.B.
Onasander 29.3, that good commanders should base their deployment off the initial deployment of
opposing forces.
44 Xenophon, Hellenica 4.2.13:
. Cf. Pritchett, 1985: 74.
Roman Infantry Tactics in the Mid-Republic: A Reassessment
11
with a Pompeian assault.45 Fighting against a numerically superior Parthian army in the
3rd century AD, Herodian (4.15.1) reports “the Romans no longer deployed their battle line in depth, but continuously extended it lengthwise to avoid encirclement”
,
›
. Perhaps the best example of mutual extension of battle
lines from the mid-Republic comes from the battle of Zama, where both Scipio and
Hannibal simultaneously lengthened their lines before the final infantry clash.46 While
mid-Republican commanders would have felt obliged to extend their line to match that
of their enemy for the sake of flank security, they seldom sought to extend their own
lines past that of their opponents. This stemmed from a cautious impulse also common
to many ancient commanders, given that overextended wings were difficult to control,
and excessively thin lines were at risk for breakthrough by the enemy.47 Roman generals
on the whole preferred to initiate flanking maneuvers either with a picked force stationed
outside of the battle line (as at Corinth and Aquae Sextiae), or through the deployment
of one of the reserve lines (as at Cynoscephalae).48
According to Polybius, each Macedonian soldier required three feet (.9m), for
himself and his weapons.49 Despite various attempts to suggest a narrower frontage for
a phalangite, I believe that .9m is indeed the correct estimate for phalangite file-width/
frontage.50 Representational evidence, particularly the Shield Monument at Veria, suggests that the Macedonian shield was approximately .70–.75 meters wide.51 The five
sarissai projecting from each file would need room as well, as each sarissa shaft had a
diameter of circa .04 meters.52 Therefore, .9 m for the file width of a phalanx is in fact
45 Caesar, African War 13, 17. interim Caesar aciem derigit simplicem ut poterat propter paucitatem
(13)….Caesar interim consilio hostium cognito iubet aciem in longitudinem quam maximam porrigi
et alternis conversis cohortibus ut una post, altera ante signa tenderet (17).
46 Hannibal lengthens lines by forcing retreating Carthaginian levies to take positions on the flanks:
Polybius 15.13.10. Scipio lengthens his line: Polybius 15.14.3. Cf. Lazerby, 1978: 224–225, Scullard
1930: 248.
47 Sabin et al., 2007: 405.
48 Corinth: Pausanias, 7.16.3; Aquae Sextiae: Plutarch, Marius 20.4, 21.1; Cynoscephalae: Polybius
18.26.1–4.
49 Polybius 18.29.2, cf. Asclepiodotus 4.1–3.
50 Delbrück, 1975{1920}: 404 suspected that .9m was actually too generous a space for a phalangite,
and that their spacing in closed order was perhaps 1.5–2 feet, based in part on an experiment conducted in a Berlin gymnasium. His students, however, while equipped with long shafts, did not have
shields. Pritchett (1971, 152–154) more cautiously suggests lowering the estimate to .8 meters, based
on the width of the Getty Museum shield, although this gives no room for the sarissa shafts!
51 Veria Monument: Markle, 1999: 246–250; The Getty Museum Shield (80.AC.60) has a width of
81.4 cm, at the upper end of the spectrum of Macedonian shield diameter. A shield monument in the
Athenian Agora, unearthed in 2010, depicts the life-sized equipment taken from a defeated enemy,
spoils which the excavator identifies as Macedonian (Camp, 2010). The shield here is .69 m in diameter, similar to those of the Veria Monument. My thanks to John Camp for allowing me to view
the monument in situ while a student at the American School in Athens.
52 Sarissa shaft diameter: Markle, 1977: 324.
12
Michael J. Taylor
somewhat conservative. File widths of .9 meters would produce a tight formation in
which shields, elbows and sarissa shafts pressed together, warranting the terms pyknosis
and synaspismos used to describe it.53 A smaller Macedonian shield, circa .6–.66m was
also in use, and is generally identified as the target used by elite peltasts.54 As such, the
frontage estimate of Hellenistic peltasts (caetri, argyaspides, etc.) should be reduced
by 10 cm to account for their smaller shields, to .8m.
Polybius assumes that a Macedonian phalanx has a standard depth of 16, but notes
the existence of double or even quadruple phalanxes, 32 to 64 men deep (12.20.10).55
Asclepiodotus (2.7) likewise places the ideal phalanx depth at sixteen men, which can
be doubled to 32. Asclepiodotus states that light troops were generally disposed in a
depth of eight (6.2), which seems to have been standard (based on the hoplite tradition),
and I will generally use this in my calculations for Hellenistic light troops.56 Based on
the tactical doctrine provided by Polybius and Asclepiodotus, it is possible to turn references to troop strength in battle narratives into frontages.57
In the attempt to tease out Roman frontages from surviving battle narratives, it is
necessary to offer my own reconstruction of various battles for which sufficient evidence
survives. In each instance, I will offer hypotheses to fill in the gray areas of the textual
evidence. There is substantial margin of error in the reconstruction of any single battle,
based on either the ambiguities in the texts or inevitable errors in my own historical
judgment. However, the case studies taken in aggregate suggest a plausible range in
the frontage of Roman legions as well as a discernable pattern in the size of implied
inter-manipular gaps.
Heraclea (280 BC): Pyrrhus landed in Italy with a heavy phalanx of 20,000, as
well as 3000 elite troops in his vanguard, likely hypaspists/peltasts.58 He subsequently
added troops from the Tarentine muster, and confronted the Roman consular army under
Valerius Laevinus at the Siris River in 280 BC. Pyrrhus deployed his Tarentine infantry
in a vanguard to secure the riverbank. After a sharp cavalry action, the legions forced
a crossing, easily disrupting the Tarentine screen. Pyrrhus deployed his main phalanx
(presumably with his 3000 “hypaspists”) and elephants, and succeeded in breaking the
legions after a prolonged clash of the main infantry lines.59
53 Asclepiodotus uses the term synaspismos to describe a specific spacing of .45 meters. Polybius
and those following him use the term more casually, usually in reference to the .9 m spacing. See
Pritchett, 1971: 151–153.
54 Hammond, 1996: 365–367; Sekunda, 2011: 461–462.
55 Arrian reports Alexander the Great deployed a phalanx 120 men deep, when pinned in extremely
narrow terrain (Anabasis 1.6.1).
56 For eight as a standard depth of Greek hoplite troops, see Pritchett, 1971: 135 (Table 4).
57 I acknowledge here that most references to strength in ancient sources presumably refer to “paper”
strength, and that most military units are inevitably understrength during operations. I will assume,
however, that both sides were understrength in roughly equal proportion.
58 Plutarch Pyrrhus, 15.1. While Pyrrhus’ force was badly battered by storms, most of his troops eventually landed in Tarentum.
59 Battle of Heraclea: Plutarch Pyrrhus, 16–17, using Hieronymus of Cardia as a source, among others.
Roman Infantry Tactics in the Mid-Republic: A Reassessment
13
If the 23,000 heavy infantry maintained a depth of 16 in close order, it would have
presented a front of 1275 meters. We must assume that Laevinus commanded a standard
consular army with two standard-strength legions (4200) and accompanying alae.60 This
would put the frontage of each of Laevinus’ legions and alae at c. 320 meters. With a
depth of 3/6 in close/open order, his maniples would require only small gaps of around
five meters apart. At a depth of 4/8 in close/open order, gaps of roughly 12 meters would
be necessary to maintain such a front. At a depth of 5/10 in close/open order, gaps of
roughly 15 meters would be necessary, although any depth beyond that would not be
feasible, as the gaps would be larger than the maniples themselves.
Cynoscephalae (197 BC): At Cynoscephalae, both armies were roughly equal in
size, at c. 26,000 troops. Philip V deployed a phalanx of 16,000, in addition to 2000
peltasts, 2000 Thracians, 2000 Illyrians and 1500 mercenaries.61 Flamininus’ two legions were c. 4200 strong, a fact that is nowhere explicitly stated, but readily deduced.
Firstly, Plutarch reports Flamininus had c. 26,000 troops, from which 6400 Aitolians,
1200 Athamanians and 800 Cretans/Apollonians must be subtracted.62 This gives a
rough estimate of 17,500 Roman troops, or 4,400 a legion/ala, counting cavalry. The
detachment previously reported by Livy (32.11.7) at the Aous Pass consisted of 4000
infantry and 300 cavalry, and is surely a single legion. Thus Flamininus’ legions were
standard strength of 4000–4200 infantry.63
Polybius reports that after sharp initial skirmishing, Flamininus drew up his legions
while Philip V hastily deployed an attack against the legion and ala on the Roman left.
Polybius claims that Philip had the right wing of his phalanx (8000 men) and 2000
peltasts.64
60 Pyrrhus had 23,000 infantry, 3000 cavalry, 2500 lights, and an unknown number of Tarentine militia.
Justin (18.1.5) reports that Pyrrhus was numerically inferior. I suspect this is only true if one counts
the second Roman army then operating in Southern Italy under the pro-consul Aemilius Barbula,
giving the Romans strategic, if not tactical superiority over Pyrrhus.
61 Livy 33.4.3–6
62 Aitolian strength: Plutarch, Flamininus 7.3. Remaining allies: Livy 33.3.9–10 (Livy is certainly
wrong on Aitolian strength, placing it at 600 infantry, rather than 6000).
63 The hastati legionis in Livy 33.1.2 are numbered at 2000 men, leading various scholars (Walbank,
1957: ii. 585; Sekunda, 1996: 36) to conclude that Flamininus’ legions were super-strength, with
200 hastati per maniple. However, the hastati legionis may instead refer to both Roman and allied
hastati combined from the legion and its allied wing, c. 2400 if each contained 4000–4200 men.
64 Polybius subsequently says that he committed to battle “with the greater part of the phalanx still on
the way” (
), although it is unclear
exactly what he means by this phrase. Polybius elsewhere uses the term pleiston meros quite casually
(e. g. 15.13.6), and as Arthur Eckstein notes, Polybius structures his entire narrative to emphasize
Philip’s haste and impetuousness (Eckstein, 1995:187–190). It should be noted that while Philip
likely began deploying his phalanx while the rear files of his right wing were still catching up, a
lull seems to have taken place that allowed Philip to organize his troops, and on the Roman side
permitted a substantial force of light infantry to withdraw through the inter-manipular gaps to the
rear. Presumably by the time the right wing of the phalanx charged, it had fully formed.
14
Michael J. Taylor
Polybius subsequently reports that Philip doubled the depth of the peltasts and
phalanx as he rushed them into position. Some have taken this to mean he assigned a
depth of 32, given that the standard depth of a phalanx was 16. I am inclined to believe
that Philip in fact merely transitioned his phalanx from a marching formation eight deep
to a standard fighting formation 16 deep, one no different from the phalanx Polybius
describes in his digression on the merits of the phalanx versus the legion which follows
immediately after his narrative of the battle.65
Philip’s light troops in his right wing consisted of 2000 Illyrians and 1500 Greek
mercenaries. His Thracians, explicitly excluded by Polybius from the light troops involved in the initial skirmish, likely comprised the Macedonian rearguard, and never
seem to have been involved in the battle, although they are listed amongst the survivors
rallied by Philip.66 In my calculations I will assume the mercenaries and Illyrians were
grouped in a “hoplite” formation with an average depth of 8 and a spacing of .9m.67
From the disposition of Philip’s right, we can roughly calculate the frontage of
Flamininus’ left, which consisted of a single legion, its paired ala and an unspecified
number of light troops.
Illyrians:
Mercenaries:
Phalanx (8000):
Peltasts
Total:
225 m
170 m
450 m
100 m
945 m
How many allied light infantry did Flamininus have on his left? We know that he had
8000 altogether, not counting his velites. Roughly 3000 auxiliary light infantry had been
part of the skirmishers, and had been received through Flamininus’ line and into his
rear.68 The remaining Aitolians did not play a major part in the battle, and according to
Polybius’ uncharitable but not necessarily inaccurate report, many slipped away to pillage the Macedonian camp.69 Most of the Aitolians were possibly among the otherwise
unattested Roman camp guard, a chore that would require roughly 2000 troops, and one
which was often tasked to non-Italian auxiliary infantry.70 The eight hundred archers
65 Hammond, 1984 initially supports the idea that the Macedonians phalanx had a depth of 32 men.
Hammond and Walbank, 1988: 441, however, place the depth at 16, representing the triumph of
Walbank’s view over Hammond’s. Cf. Walbank, 1957: ii 583, Barnes, 2005: 357, Sage, 2008: 173.
66 Thracians excluded from Philip’s right: Polybius 18.22.2. Rallied by Philip after battle: Polybius
18.26.9.
67 Illyrians as a rule fought in a phalanx-style formation in the manner of Greek hoplites (Vegetius 2.2).
68 Polybius 18.21.5, Livy 33.7.9. 2000 of these are identified as mostly Aitolians. The first 1000 of
the light infantry were not Roman, given that Polybius identifies them as
, rather than
, his usual terms for Roman velites. It certainly made more sense to detach Greek
infantry rather than velites, to maintain the unit integrity of the legions. Also, in sending forth Apollonians or Aitolians, he would have been dispatching men more likely to be familiar with the terrain.
69 Polybius 18.27.4 cf. Eckstein, 1987: 288, n.79.
70 2000 strong camp guard (at Magnesia): Livy 37.39.12.
Roman Infantry Tactics in the Mid-Republic: A Reassessment
15
were likely interspersed among the infantry, rather than fighting as a single battalion.
The number of light troops deployed in Flamininus’ left wing was therefore roughly
2000. These would have a front of approximately 225 meters. This meant that the Roman legionary line on the left wing, one ala and one legion, covered approximately 720
meters, or 360 for a single legion. If the maniples maintained a depth of 3/6 in close/
open order, they would require gaps of roughly nine meters. If they maintained a depth
of 4/8 in close/open order, the gaps would need to be 16 meters to maintain this front.
A close/ open order depth of 5/10 or more would not be possible, given that the gaps
would by necessity be larger than the maniple frontages.
Magnesia (190 BC):
The battle of Magnesia was one of the great lopsided
victories in ancient history, as nearly 30,000 Roman and Attalid troops crushed the
72,000-strong army of Antiochus III. The Seleucid infantry line was anchored by its
main phalanx, 16,000 men strong, 32 men deep, divided into ten divisions. There were
two elephants in each interval, with supporting light troops. I will place the total frontage of the phalanx and elephants at 550 meters (450 for the phalangites themselves,
with 100 meters estimated for the elephants and supporting light troops).71 On either
side of the phalanx were two divisions of Gallic infantry, 1500 men each. While I have
generally assigned light infantry a depth of eight, Antiochus III arrayed his forces with
increased depth, and it makes sense he would compliment his double-deep phalanx
with extra-deep ranks of supporting light infantry. I will therefore hypothesize a depth
of 12 to the Galatian infantry. A depth of 12 provides a neat coincidence, as it would
suggest that the remaining 4700 infantry (2000 Cappadocians and 2700 mixti) between
the Galatians and the left division of Seleucid cavalry had a front of 350 meters, almost
equal to the frontage of the 3000 Achaean and Attalid light infantry opposite them, if
these maintained a standard depth of eight.
Antiochus’ right wing presents a puzzle. Livy suggests that to the left of the main
phalanx and its screen of 1500 Galatians was posted first 3000 cataphracts, then 1000
cavalrymen of the Agema, and then in the infantry of the Silver Shields, which if correct
would provide a rare instance of a heavy infantry unit being placed on the extreme flank
of a cavalry unit. It would also be a major deviation from Hellenistic tactics, as since
Alexander the elite infantry guard unit had traditionally been posted to the immediate
right of the main phalanx.72
However, Polybius’ fierce derision of Zeno’s account of the Battle of Panion (c. 200
BC) provides some insight into what Antiochus may have been doing with his right wing.
Polybius’ criticism is profoundly confused in its own right, but he rails against Zeno for
claiming that Antiochus here placed a brigade of Tarantine cavalry, along with his own
“companion” cavalry in front of the main phalanx.73 Despite Polybius’ uncharitable cri71 Bar Kochba, 1979: 167 gives each elephant ten meters; five meters per elephant seems more than
sufficient to me.
72 On the conservatism of Hellenistic tactics: Lendon, 2005: 143–145.
73 Polybius 16.18.7–10:
›
,
16
Michael J. Taylor
tique, it is likely Zeno was correct, and that Antiochus was experimenting with cavalry
charges followed up by infantry assaults.
It is quite possible that Antiochus effected a similar arrangement at Magnesia, but
Livy (or his source, most likely Polybius himself) has simply become confused, placing the Silver Shields on the flank of the cavalry. Rather, I suspect Antiochus stretched
out the unit (Livy claims it deployed cornu producto) to provide a tactical base for his
heavy cavalry deployed to its front. This way, the king could focus his cavalry charge
against the legions without worrying about opening a gap in his own front, while the
Silver Shields could also be used as a mopping up force after the cavalry charge had
shattered the legions.
The cornu productum did not have to be deep, given that it stood behind over 4000
heavy cavalry. In fact, it is plausible to assume that for this purpose a depth of eight men
would have been entirely adequate, producing a frontage of approximately 1000 meters
assuming the Silver Shields maintained a strength of 10,000.74 If the 16 elephants on
the left wing were placed in support in a manner similar to those in the main phalanx,
this would extend the line another 80 meters, for a total of 1080 meters. This correlates
approximately with the c. 900 m frontage of 4000 cavalrymen in Thracian/Macedonian
wedges (in which, following a fragment of one of Polybius’ lost tactical writings, each
wedge contains 64 men, with a base of 16, and a file width of .9 per horseman), although
we have no evidence for the specific formation used by Antiochus’ cavalry.75 On this
hypothesis, the entire Seleucid line facing the legions would have been:
Phalanx and elephants:
Silver Shields and cavalry:
Galatians:
Total:
550 m
1080 m
225 m
1855 m
This would imply that each legion and ala at Magnesia had a front of c. 465 m. Livy
reports each legion had a strength of 5400 infantry, with equal numbers in the allied
ranks. This implies 1600 hastati per legion and ala. If they maintained a close/open
depth of 3/6 ranks, the hastati would physically occupy 360 meters, implying an average gap of c. 10 meters. With a close/open depth of 4/8, the physical front of the hastati
would be 270 meters, requiring the gaps cover c. 20 meters apiece. A close/open depth
of 5/10 or more would not be possible, given that the gaps would by necessity be larger
than the maniple frontages.
,
. See Xenophon, Hell. 6.4.10 for similar deployment of cavalry in the van of a Greek
heavy infantry formation.
74 Bar Kochba, 1979: 8–9, 168 argues staunchly, and in my opinion correctly, that the unlisted strength
of the Silver Shields must be 10,000, based on the unit’s listed strength at Raphia, and the fact that a
strength of 10,000 helps make Livy’s various contingents add up to his stated total of 60,000 infantry
fighting for Antiochus III.
75 Aelian, Tactica, 19.5–10. They would have a similar frontage if deployed in the manner described
in Polybius 12.18.
Roman Infantry Tactics in the Mid-Republic: A Reassessment
17
Pydna (168 BC): Pydna was by all accounts a confused engagement, as both sides
hastily formed battle lines after a brawl over a runaway horse escalated into a setpiece battle, on a broad plain roughly 4 km long.76 Perseus’ heavy infantry consisted
of phalangites divided into two divisions of roughly 10,000 each, the leukaspides and
chalkaspides (White Shields and Bronze Shields), along with a brigade of 5000 peltasts
(Livy’s caetri). The king had in addition an enormous force of c.13,000 light infantry.
Many of the details of the battle are swallowed up in an unfortunate lacuna in Livy.
Nonetheless, if Perseus managed to eventually deploy roughly 11,000 light infantry
(subtracting a modest camp guard), his total battle line would consist of:77
Main phalanx (20,480):
Peltasts (5000):
Light infantry (11,000):
Total:
1152 m
281 m
1237 m
2670 m
The exact number of Greek light infantry fighting on the Roman side at Pydna is not
stated, but earlier the Romans had been joined by 4000 Attalid infantry, 1500 Achaeans
and 100 Apollonians.78 Subtracting 2000 for a camp guard, the remaining Greek infantry
would take up c. 400 meters, leaving 2270 meters for the legions and alae, or a frontage
of c. 570 meters apiece. This frontage is confirmed by Livy’s report (perhaps following the eyewitness account of Scipio Nasica) that Paullus’ I Legio directly engaged the
chalkaspides and that II Legio deployed against the leukaspides.79 Each phalanx had a
paper-strength of 10,240 men, giving the two opposing legions a frontage of c. 575 m
apiece – almost identical to the figure adduced above.80
Each legion consisted of 6000 infantry, and this would imply 1800 hastati.81 If a
close/open depth of 3/6 was maintained, the hastati themselves would occupy 405 meters. To maintain a total front of c. 570, gaps of c. 17 meters would be necessary. If each
maniple maintained a close/open depth of 4/8 men, the hastati would occupy 300 meters,
76 For the physical setting of the battle, see Hammond, 1984: 39–40.
77 Infantry survivors include 500 Cretans (Livy 44.43.7) and probably the 1000 Thracians associated
with Cotys (who led the retreat, Livy 44.42.2). These perhaps comprised the bulk of the Macedonian
camp guard (Perseus also seems to have been surrounded by a large force of cavalry which was not
deployed in the battle).
78 Livy 42.55.7–10. This does not count 2000 Attalid troops used to garrison Chalcis.
79 Erdkamp, 2006 argues that Plutarch’s account of Pydna derives in part from a Late Annalistic source,
which frequently featured numbered legions. While he is quite correct, this need not negate the
veracity of the account. Outside late annalistic sources, numbered legions are attested in a fragment
of Cato, see Agnew 1939.
80 Livy implies the strength of the two phalanxes was roughly 21,000 at the start of the war (42.51,
subtracting 18,000 enumerated auxiliaries and peltasts from the total infantry strength of 39,000).
Perhaps the “paper strength” here was 10,240, or 10 chiliarchies. The suggestion in Haztopoulos,
2001: 75 that each phalanx division had a strength of 12,000, or 24,000 total, is dubiously based on
the number of wagons displaying captured shields at Aemilius’ triumph.
81 Livy 44.21.8.
18
Michael J. Taylor
requiring large gaps of roughly 27 meters. A close/open depth of 5/10 or greater would
not be feasible, given that the gaps would need to be larger than the maniple frontages.
Corinth (146 BC): Mummius fielded a total of 23,000 Roman and Italian infantry.82
Subtract his picked detachment of 1000 infantry which was designated as a flanking
force, along with a modest camp guard and some Italian soldiers deployed to a forward
outpost, and it is a reasonable assumption that his main infantry line consisted of 20,000
troops, with each legion and ala having an average strength of c. 5000.83 The Romans
faced a numerically inferior force of 14,000 Achaean infantry. These were presumably
drawn up in standard hoplite form, eight deep, producing a line 1575 meters long.84 This
would give each legion and ala a front of around 395 meters. If Mummius wished, he
could deploy his troops 3/6 deep in close/open order and maintain his maniples seven
meters apart. With a close/open depth of 4/8 ranks, gaps of roughly 15 meters would
be required to maintain this frontage. A close/open depth of 5/10 or more would not
be possible, as this would require the gaps to be larger than the maniples themselves.
Table 2: Induced Frontage of Roman Legions
Battle
Induced
Legion
Gaps
Front
Strength (depth 3/6)
Heraclea
c. 320 m
4200
5m
Cynoscephalae: c. 360 m
4200
9m
Magnesia
c. 465 m
5400
10 m
Pydna
c. 570 m
6000
17 m
Corinth
c. 395 m
5000
7m
Mean
10 m
Gaps
(depth 4/8)
12 m
16 m
20 m
27 m
15 m
18 m
Gaps
(depth 5/10)
15 m
x
x
x
x
15 m
Conclusion: Minding the Gaps
Constructing the Roman acies with reference to Macedonian battle lines suggests a
range of frontages for a mid-Republican legion between 320 and 570 meters, with larger legions having longer frontages. This analysis suggests that the Romans did indeed
maintain gaps in their formations during combat (see Table 2 for a summation). The
gaps varied substantially based on tactical circumstances, but gaps of c. 10–20 meters
82 Presumably the allied wings were somewhat stronger than the legions, say 5200 apiece in the legions
and 6200 for the alae.
83 These were joined by some Cretan archers who were most likely interspersed through the ranks, and
some Attalid light troops, who were stationed in a forward outpost that was subsequently overrun
by the Achaeans.
84 Battle of Corinth: Pausanias 7.15.7–16.3 While Plutarch reports that Philopoemen had equipped
the Achaeans to fight as a Macedonian-style phalanx, which might imply a depth of 16, Pausanias
(8.50.1) suggests that the Achaeans in the 200s in fact retooled from fighting as thureophoroi light
infantry into relatively standard Greek hoplites, fighting with Argive shields, and presumably in an
8 man hoplite formation. See Anderson, 1967.
Roman Infantry Tactics in the Mid-Republic: A Reassessment
19
may have been relatively standard. It is notable that this evidence does not suggest that
the gaps were usually equal to the width of an entire maniple, but rather were generally
25–75 % the width of a maniple front.
The accordion nature of the Roman legion was perhaps one of its major tactical
strengths. A commander and his subordinates could easily expand or shrink his front
based on the nature of the terrain, the character of his troops, or the strength and disposition of the enemy. For example, the legion spearheading Flamininus’ drive through the
Aous pass would need to contract or expand from 200 to 400 meters, as the restricted
terrain narrowed or widened.85 Acilius Glabrio, assaulting the gate at Thermophylae,
likewise arranged his legions in a narrow front to fit the topography: ad naturam et angustias loci.86 Empty space between the maniples provided much of the tactical flexibility
enjoyed by the legion, as frontages could easily be expanded or compacted simply by
altering the size of the gaps, without compressing or dispersing the soldiers within the
maniples themselves. These flexible frontages allowed invading Romans to fix large
numbers of enemy troops with elongated fronts, negating any numerical advantages
possessed by opposing forces, so that at Pydna 6000 men in a legion could match over
10,000 drawn up in a Macedonian phalanx.
Gaps would provide sufficient space for light forces to be expeditiously received
through the hastati, and facilitate exchange and relief between the lines of the tres acies.
Infiltration by enemy soldiers would be discouraged by the fact that the gap could be
completely covered by missile crossfire from the Romans stationed on the flank of the
surrounding maniples. The stationing of the principes immediately behind allowed for
immediate reinforcement in the event that the hastati buckled at these weak points.87
It is unlikely that these gaps were completely “empty” during combat. The gaps
would also be ideal for the employment of auxiliary light troops such as archers and
slingers, as when Sallust reports that Caecilius Metellus “dispersed slingers and archers in
between the maniples” inter manipulos funditores et sagittarios dispertit.88 While velites
in theory withdrew to the rear, a number of ambitious young men may have lingered in
the gaps for the opportunity to score an extra kill. The gaps thus helped integrate light
troops into the matrix of heavy infantry. When the Roman army deployed elephants,
as it did at Cynoscephalae and Pydna, these were likely initially stationed in the gaps,
while Scipio famously used his gaps to channel Hannibal’s elephants at Zama.89 Finally,
85 Hammond, 1966: 50. With a 4200 strong legion and a depth of 8, this would involve gaps transitioning between 0–20 meters.
86 Livy, 36.18.2.
87 Adcock, 1940: 9–10; Sabin, et al., 2007: 429. Polybius 15.13.3 suggests that the principes at Zama
were stationed quite close behind the hastati, in contrast to Hannibal, who had over a stadion (180
meters) between his first and last battle lines (15.11.2).
88 Sallust, Jugurthine War, 49.6. This is also the last textual notice of maniples serving a tactical role
in combat. Cf. Herodian 4.15.1, for a similar use of inter-unit gaps in AD 217.
89 Polybius 15.9.7.
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Michael J. Taylor
if any enemy ventured into this lethal funnel, Roman soldiers on either side of the three
surrounding maniples might peel off to engage them.
In addition to providing flexibility to the commander, gaps in the maniples contributed to the maintenance of the basic tactical integrity of the entire legion. Gaps
prevented bewildered soldiers, whose training and experience might vary substantially,
from becoming intermingled with other units, and allowed haphazardly maneuvering
maniples to avoid entanglement. Indeed, Rome’s greatest disasters occurred when the
gaps were narrowed or eliminated, most notably at Cannae.90 Without the presence of
moderate gaps, the Roman legion risked becoming a chaotic and unfocused mass.
The relatively shallow line of legionary infantry, punctuated by gaps, was not without
its weaknesses. In particular, it was highly vulnerable to shock charges, evidenced by the
retreat of legionary elements before Philip V’s right wing at Cynoscephalae, Antiochus
III’s cataphracts at Magnesia and Perseus’ dazzling phalanx at Pydna. In each instance,
however, the legions were able to reorganize and counterattack. It is possible that the
inter-manipular gaps helped prevent the outbreak of mass panics or mob retreats, by
insulating adjacent units from the communal psychological stresses generated within a
hard-pressed maniple.91 Ultimately, the flexible frontage and tactical modularity inherent in the manipular legion must remain a significant factor in explaining the relative
success of the mid-Republican army on the battlefield.
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Department of History
University of California, Berkeley
3229 Dwinelle Hall
Berkeley, CA 94720-2550
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Michael J. Taylor