An In-Depth Guide to the Army of the Seleucid Empire

At its height in 281 BCE, the Seleucid Empire spanned from the western coast of modern-day Turkey to the borders of the Mauryan Empire in India. Although these armies would have been led by Macedonian kings and generals, the Seleucids, more so than their contemporaries, utilized native contingents and military traditions to bolster the Greco-Macedonian phalanx.

The three most detailed accounts of the Seleucid army are found in the ancient accounts of the battle of Raphia, the battle of Magnesia, and Antiochus IV’s military procession at Daphne. In each case, a great deal of focus is placed upon the non-Macedonian elements: mercenaries from the eastern provinces, elephants, chariots, cataphracts, as well as soldiers armed “in the Roman style”.

The Greco-Macedonian contingents played an extensive role within the Seleucid army. The Seleucid Monarchs considered themselves successors of Alexander the Great and wished to emulate him. This emulation was expressed, among others, with campaigns led from the front by the king leading to the violent ends of several Seleucid monarchs, such as Seleucus VII Sidetes, who died while leading his army at Ecbatana in 129 BCE. To further the connection with Alexander, the Seleucid monarchs maintained or revitalized regiments from Alexander’s conquests. Polybius (31.3) details that among the regiments present at Antiochus IV’s military procession at Daphne were the “companion cavalry” — the elite Macedonian cavalry — as well as “Macedonians” (ie units equipped and trained to fight in the Macedonian phalanx formation). Another group mentioned by Polybius was the “armed with silver shields,” which is used by scholars such as Bezalel Bar-Kochva to suggest that the “infantry guard” of the Seleucid Empire would have been the Argyraspides (literally translating to Silver Shields). It is important to note that both the Companions and Argyraspides appeared within the army of Alexander the Great, which indicates a desire for continuity between the Seleucids and their descendants. However, the Argyraspides were disbanded during the Wars of the Diadochi, with Plutarch stating:

“Antigonus himself, detesting the Argyraspides as impious and savage wretches, ordered Sibyrtius, governor of Arachosia, under whose direction he put them, to use every method to destroy them; so that not one of them might return to Macedonia, or set his eyes upon the Greek sea”
(Plutarch, Life of Eumenes, 19.2)

The fact that these previously discarded regiments of Alexander the Great’s army had been revived by the time of Antigonus IV indicates that the Seleucid rulers perceived their army as a continuation of Alexander’s.

The “Template of the Seleucid Army

A typical Seleucid army consisted of Macedonian-styled “Phalangite” infantry, each wielding a 15ft sarissa pike, with cavalry on either flank to act as a flank guard and to maneuver around enemy formations and attack them from behind. This formation is best recorded by Polybius in the Battle of Raphia:

“The two sides formed up in very similar formations, with the phalanx in the center flanked by the lighter troops and cavalry. Ptolemy took up position on his left flank, Antiochus opposite him on the Seleucid right”
(Polybius V.65)

It should be noted that the right flank was often seen as a place of honor in the Hellenistic period, as a result of Alexander often appearing on this flank, further connecting the Seleucid’s identity to Alexander. Although reminiscent of Alexander’s, these formations would sometimes hinder the military success of the Seleucid Empire. If one looks at battles between the Seleucids (or any other Hellenistic Kingdom) and the Romans, one will see that the rigidity of the Macedonian Phalanx was exploited by the much more maneuverable maniple.

The maintenance of this tactic throughout the Hellenistic period must therefore be seen as a cultural decision on the part of the Greco-Macedonian elite. The reason is that even though more flexible tactics were developed in the Seleucid Empire, the phalanx-based tactics remained. To the phalanx, a series of settlements were constructed across the Seleucid Empibolster re. These settlements (some of which developed into cities) were populated by Greeks and Macedonians, known as the Katoikoi, who received land and settled status in these settlements in return for their military service.

The importance of Greco-Macedonian culture within the Seleucid Empire can therefore not be overstated. From the overall structure of the battle line to the mindset of the monarchs that led these armies, Alexander the Great’s legacy remained imprinted upon the Seleucid army and military culture.

Local, non-Greek military culture played a key role in the armies of the Seleucids throughout the Hellenistic period. In a similar manner to all the Hellenistic Kingdoms, the Seleucids would have made use of mercenaries fighting in their own traditional styles. These native, non-Greek regiments also saw regular use in the regular army. In many cases, they were used to further increase the effectiveness of the phalanx and the Macedonian way of war.

One such example would be the use of Cataphracts, a type of cavalry that had both horse and rider covered in heavy armor. This style of cavalry, which may have developed by Iranic peoples hundreds of years prior to the Hellenistic Period, was widely used by the Seleucid army in battles such as Magnesia, where the Seleucid king Antiochus III battled against the Roman Republic:

“and with them were linked up 3000 cavalry, clad in mail armour and known as cataphracti.”
(Livy 37.40)

Although these cataphracts were largely ineffectual during this battle, the entire Seleucid line had already been disrupted by the abysmal performance of Antiochus’ scythed chariots.  The way in which the Seleucids may have used cataphracts more efficiently against the Romans can become evident from other battles. An example of the devastating impact of cataphracts comes from the battle of Carrhae (53 BCE), when the Roman army under Crassus was attacked by Parthian cataphracts:

“many died from fright at the very charge of the pikemen, and many perished hemmed in by  the horsemen. Others were knocked over by the pikes or were carried off transfixed”
(Cassius Dio 40.22)

The Seleucid King’s Cavalry Guard: Companion and Median Cavalry

The effect these horsemen would have on the battlefield could be immense, especially when considering that cavalry was often used as the “hammer” to the phalanx’s “anvil”, charging into the rear of the enemy while they were being held back by the phalanx. This need for effective cavalry can also be seen in the second aspect of the king’s cavalry guard, the Companions and the Agema.

The Seleucid monarch would have been guarded by the Companions as well as the Agema, who, according to Livy, were picked men who specifically originated from Media, a region of Iran. The Median Cavalry was utilized by the Seleucids since the very beginning of the Hellenistic Period. Diodorus Siculus details that Seleucus I brought 12,000 cavalry from the eastern satrapies to the Battle of Ipsus (Diodorus 20, 113). Scholars believe that a certain type of Seleucid coinage from a hoard at Bactria, depicting eastern symbols such as the star, crescent, and horse, was used specifically to pay Median horsemen. Once again, the skill of these horsemen would have been used to provide to guard the phalanx’s sides and maneuver around the enemy for an efficient “hammer and anvil” tactic.

Another non-Greek regiment used by the Seleucids was the elephants. Elephants were used extensively by Hellenistic monarchs throughout the Hellenistic Periods. However, the Seleucids used elephants more than every other Hellenistic Kingdom.

After his failed invasion of India, Seleucus I was gifted five hundred war elephants by the Mauryan king Chandragupta. This earned Seleucus the nickname “Elephantarkos” or “Elephant Lord”. These elephants would be used at the Battle of Ipsus to block Demetrius’ cavalry from returning to the battlefield and attacking the rear of his own phalanx. After this, the Seleucids made heavy use of elephants to break the spirit of their enemies who were faced with the gigantic animals’ thunderous charge.

Even after the Treaty of Apamea in 188 BCE, where the Romans forced Antiochus III to kill all of his elephants and never make use of them again, it only took twenty years for Antiochus IV to break this clause of the treaty, as seen in the Daphne procession:

“a chariot drawn by four elephants and another by two; and then thirty-six elephants in single file with all their furniture on”
(Polybius 31.3)

Roman-Style Infantry

According to Polybius’ description of the Daphne procession, among the soldiers present there were some “armed in the Roman fashion.” Archaeological evidence to back up this claim exists in a funerary stele in Sidon which depicts two Seleucid soldiers (Salmamodes and Dioskourides) wielding weapons like their Roman contemporaries (short swords, oval shields, short spears, etc.). Bar-Kochva concluded that these men, who were “in the prime of their life,” would have been members of the Argyraspides, the infantry guard of the Seleucid monarch. This is important when placed in context alongside the fact that, as the royal guard, the Argyraspides would have been placed on the right flank of the battle line. This would place the tactically flexible Argyraspides on the vulnerable flank of the phalanx and, being able to be armed as both a phalangite and a more tactically flexible Romanesque soldier, could guard the weakest point of the battle line.

Overall, the Seleucids made tactically intelligent use of the military traditions of the native cultures that lived under their empire while maintaining an overall Greco-Macedonian template on which they based their army. The phalanx remained the core infantry formation throughout the Hellenistic period, with more flexible heavy infantry used to guard the vulnerable flanks of the phalanx. The cavalry still acted as a “hammer” for the traditional Macedonian “hammer and anvil”. However, this tactic was enhanced with skilled Iranian-styled horsemen. More “exotic” tactics featured the use of elephants and chariots used to disrupt infantry lines and further increase the efficiency of the phalanx and cavalry. Non-Greek regiments were therefore, mostly used by the Macedonian rulers of the Seleucid empire as tools to increase the effectiveness of the Macedonian way of war that was ultimately passed down to them by Alexander the Great.