Legions and Phalanxes: Examining Roman Success During the Hellenistic Era
The period following the death of Alexander the Great is known as the Hellenistic Era, a point in history which witnessed the fracturing of Alexander’s empire into multiple Hellenistic states. The latter stages of the Hellenistic Era saw the rapid ascendance of Rome from a regional power to a dominant force in the Mediterranean. This paper aims to explore the tactical nuances and organizational structures of the Roman military system and compare it to that of the Hellenistic successor kingdoms. The distinct military structures and tactical approaches of the Roman legions and the Hellenistic phalanxes were pivotal in determining the outcomes of their encounters during the Hellenistic period. Rome’s more flexible formations and adaptive tactics often proved decisive against the more rigid formations of the Hellenistic armies, playing a crucial role in Rome's rise to dominance in the Mediterranean world.
To understand the Roman Army during this period, it is critical to examine what can be described as the functional unit of the Roman Military: the Legion. As described by Greek Historian Polybius in his Histories, each Roman Legion usually comprised about 4,200 infantry and about 300 cavalrymen, usually deployed at either flank of the legion.[1] In battle, legions were divided into three distinct lines, based on how long these soldiers had served. The first line of a Roman Legion in battle was called the Hastati, which was composed of the youngest soldiers, with the least experience in battle.[2] The second line was the Princepes, and the third the Triarii. The Princepes were soldiers considered to be “in the prime of their lives,” and the Triarii older veterans who had likely been on multiple campaigns.[3] In battle, the Hastati would be positioned at the very front, with the Princepes behind them, and the Triarii at the back of the legion.
The armaments of a Roman legion were also divided according to line. The Hastati were equipped with heavy javelins for throwing at enemy lines and punching through shields (known as a pila) as well as a short sword, known as a gladius.[4] Accompanying these weapons was the scutum, a large curved rectangular shield which provided protection against both enemy missiles and in hand-to-hand combat. The Princepes were equipped similarly to the Hastati, with pila and gladii. However, they were more heavily armored; their role was to engage after the Hastati, using their experience and heavier armor to press the attack and exploit any weaknesses opened by the Hastati. The Triarii were intended to be a final reserve, or last line of defense for the legion, and were the most heavily armed, carrying the gladii and scutum alongside long spears called hastae.
Alongside these three lines of a Roman Legion were soldiers known as the Velites, numbering about 1200 in each legion.[5] These soldiers were lightly armored, carrying a short sword, a smaller, round shield, and a bundle of javelins. Polybius writes that these javelins had their points sharpened such that they would bend upon first impact, rendering them unusable by the enemy.[6] Their role in battle was essentially that of light infantry, or skirmishers. They would be used to disrupt enemy formations prior to the engagement of the heavier infantry, and to protect the rest of the legion from enemy skirmishers. As they had no set battlefield position, they could quickly transition from skirmishing to retreating into the heavier infantry's lines.
These lines of the Roman Legion were further subdivided into groups called “maniples” during combat. These maniples consisted of two “centuries” of 60 men, each with its own commanding centurion. These units of men would stand in a checkered formation, with the more experienced maniples standing behind the gaps formed by the staggering of the lines ahead of themselves.[7] This Manipular system allowed the flexibility of the Roman Legion in a variety of ways. First, the arrangement of the legion due to this staggering of maniples essentially allowed for the function of the Velites; these structural gaps allowed for a quick method of retreat after the deployment of their javelins. In addition to this, the manipular system also allowed for a level of command decentralization; the two centurions in each maniple could make tactical decisions at a unit level, allowing for a maniple’s rapid response to changing battlefield conditions. This meant more situational maneuverability and adaptability for individual maniples.
The manipular system was ultimately phased out at around 108 BC during the Marian Reforms in favor of the Cohort system, a similar system dividing the Roman Legion, but with 480 men in a cohort rather than the maniple’s 120.[8] However, as the manipular system defined the Roman approach to battle for most of the Hellenistic Era, this paper uses it as a basis for comparison to the armies of Hellenistic successor kingdoms.
In comparison to the legions of the Roman Army, the armies of Hellenistic succesor Kingdoms usually more closely resembled the armies of Alexander the Great. Therefore, for most such Hellenistic armies, the Phalanx, or slight variations on the phalanx was the infantry formation of choice. Supporting the phalanx would be the Cavalry, and various other ancillary troops.
Central to the phalanx was the sarissa, a pike of such length that it demanded both hands to wield effectively. Arranged in rows, the phalanx's sarissas presented multiple layers of deadly points to the enemy, with the front ranks holding their pikes at thigh level, those behind raising their pikes overhead.[9] Shields in these phalanxes would typically be smaller and suspended from the neck to allow better handling of the spear.
However, the phalanx’s compact structure came with several significant drawbacks. One of the primary limitations of phalanx formation was its lack of lateral mobility. The phalanx’s tight formation was not especially maneuverable, and thus vulnerable to flanking maneuvers.[10] If an enemy force could get to the side of the phalanx, the formation's effectiveness was significantly diminished, as the soldiers could not easily turn to face the new threat without breaking formation. Terrain also posed significant challenges to the phalanx. While highly effective on flat, open terrain where its compact structure could be easily maintained, more difficult terrain such as hills, forests, or uneven fields, the formation's cohesion could be compromised, reducing its combat effectiveness.[11]
However, the phalanx was not the only aspect of Hellenistic armies. The cavalry was commonly deployed on the flanks of the phalanx in battle.[12] This deployment attempted to minimize the weakness of the phalanx ‘s limited options for response to flank attacks. Light cavalry would often carry light javelins and bows, serving as reconnaissance units. During battle, they would engage in skirmishes, and harass the enemy’s flank with long-range weapons. Heavy cavalry carried longer lances and wore armor. Heavy cavalry would be employed to exploit gaps, or other breaches in the enemy’s ranks created by the phalanx, charging in to break through and sow chaos through the enemy lines.[13]
Beyond the phalanx and cavalry, the armies of Hellenistic Kingdoms also commonly employed auxiliary troops. These were often non-native troops and varied from conflict to conflict. However, they usually softened up enemy formations prior to the phalanx's advance and provided additional support for the flank or rear of the phalanx. Such ancillary troops might include slingers, archers, or peltasts. These troops were valuable as they increased the tactical versatility of these Hellenistic Kingdom’s armies, shoring up areas of natural weakness.
Another aspect of some Hellenistic armies, particularly that of the Seleucid Empire, was the usage of war elephants. These massive animals, often clad in protective armor, were introduced into Hellenistic warfare following Alexander the Great's campaigns in India, where he encountered them. Primarily, war elephants functioned as a form of psychological warfare; their sheer size and strength were very intimidating. Elephants were also used to charge enemy lines, their power and momentum capable of breaking through infantry formation and causing disarray.[14] They also played a defensive role, being placed on flanks or other important positions to deter enemy cavalry charges.
This contrast in tactical approaches and military composition between the Roman legions and the Hellenistic armies, particularly those of the Seleucid Empire, was illustrated during the Battle of Magnesia in 190 BC. During this period, Antiochus III, the Seleucid king, embarked on military campaigns to expand his empire's territory. His efforts to extend Seleucid power into Asia Minor directly challenged Rome's sphere of influence, particularly in territories that Rome had placed under its protection. This expansionist policy by Antiochus III inevitably led to escalating tension, culminating in open warfare between the Roman Republic and the Seleucid Empire. The ensuing battle at Magnesia stands as a critical case study, highlighting the Roman military's adaptability and tactical flexibility in the face of the forces of a Hellenistic army.
The main source this paper uses for its examination of the Battle of Magnesia is Appian’s “Syrian Wars.” It must be recognized that Appian is a Roman historian, and quite obviously biased in favor of the Roman side, calling Antiochus III “Light-minded” within the first few lines of his description of Magnesia.[15] He also seems to like to dramatize the actions of the people he describes.
As described by Appian, the Battle of Magnesia began with the deployment of both armies. The Seleucids deployed a phalanx in the center, with cavalry and 22 elephants fanning out on the phalanx’s either flank. Ancillary troops, including archers, peltasts, and slingers were also deployed in the front and rear.[16] The Roman legions, led by Lucius Cornelius Scipio Asiaticus and his brother Scipio Africanus and allied armies were deployed side-by side, the cavalry also deployed on either flank. The Seleucids numbered about 70,000, while the Romans numbered about 30,000.[17]
As the battle commenced, the initial engagement was marked by a series of maneuvers and skirmishes carried out by the Roman Velites, as the legion did not want to face the phalanx headon. Later in the battle, the Seleucid war elephants were made to charge towards the Roman lines with the intention of causing chaos and breaking the cohesion of the legions. However, when this occurred, instead of holding their ground against the charging elephants, the Roman soldiers created gaps in their lines, allowing the elephants to pass through with minimal disruption, and attacking the elephants from behind with spears.[18] In contrast, when the Roman Velites used their light javelins to harass the Seleucid war elephants back into the lines of the phalanx, it sowed havoc among the ranks of the phalanx. The Roman Army quickly took advantage, striking at the phalanx’s weak, exposed flanks. This maneuver completely neutralized the phalanx’s frontal assault capabilities, and ultimately led to the Seleucid Army’s overwhelming defeat, despite their advantage in sheer numbers.
The Roman victory at Magnesia highlights the effectiveness of the manipular legion system, and the adaptability on the battlefield associated with it. In contrast, the phalanx formation was shown to be vulnerable in the face of this more versatile opponent, which took advantage of the phalanx’s inflexibility. It was these dynamic and adaptable military strategies that allowed Rome to come to prominence over Hellenistic successor kingdoms militarily throughout the Hellenistic period.
Notes
[1] Polybius, Histories, 6.20
[2] Hastati, Princepes and Triarii all refer to both the line, and the individual soldier.
[3] Polybius, Histories, 6.20
[4] Goldsworthy, The Complete Roman Army, pg. 28
[5] Polybius, Histories, 6.21
[6] Ibid, 6.22
[7] Taylor, Michael J. “ROMAN INFANTRY TACTICS IN THE MID-REPUBLIC: A REASSESSMENT.” Historia: Zeitschrift Für Alte Geschichte 63, no. 3 (2014): 301–313.
[8] Goldsworthy, p28
[9] Warry, Warfare in the Classical World, p73
[10] Ibid, 68-69
[11] Ibid, 96-97
[12] Most diagrams of battles in the Hellenistic Era display cavalry at the flanks, and other lighter auxillary troops at the flank or rear of the phalanx.
[13] Warry, 73
[14] Ibid, 93
[15] Appian, The Syrian Wars 6
[16] Appian, 7
[17] Throughout the texts I’ve read, this number varies a lot. Some estimate their forces to be about the same. This estimate is on the higher ranges in terms of how many soldiers the Seleucids had.
[18] Ibid, 7