(This is the first part in a series on the militaries of the Macedonian Successor states; which grew out of the Wars of the Diadochi that followed the death of Alexander the Great. For the next century after his death, these kingdoms were defended by armies that represented the greatest fighting forces in the Hellenistic World. Each differed from the other in fascinating ways, as will be shown.)

Of the empires created from out of the Wars of the Diadochi, none started on firmer military footing than that founded by Seleucus Nicator (“the Victorious”; or, alternately, “the Conqueror”).

1375374.jpgAt the time of his murder in 281 BC, Seleucus command (arguably) mightiest army the world had yet seen. He had defeated, and then combined with own, the armies of his erstwhile rivals Antigonus Monophthalmus (“One Eyed”) and Lysimachos. Put another way, of the four great Macedonian Successor armies fighting at Ipsus in 301 BC (twenty years earlier), all of the some 160,000 combatants now served Seleucus.

Within were men that had been junior rankers under Philip and Alexander; who had first conquered Greece and then laid “the whole of Asia” (for that is how they thought of the Persian Empire they had subdued) beneath their spears . These were hard men who had marched across the Middle East and back; veterans of the greatest campaigns and most titanic battles of the age. This force represented the combined experience and victorious tradition that was the Macedonian military machine founded by Philip and perfected by Alexander.

1375376.jpg Seleucus I Nicator

Seleucus was assassinated by an estranged son of Ptolemy Soter, King of Egypt. A portion of his “Grande Armee” chose to serve the assassin, the freebooting prince Ptolemy Keraunos. Presumably these were the veterans of Lysimachus’ army, only newly enlisted in Seleucus’ service after their master’s death at the Battle of Corupedion, and with scant loyalty to the House of Seleucus. Ptolemy Keraunos used them to seize the throne of Macedonia for himself. The rest of Seleucus’ army either dispersed or returned east; to be settled by his son, Antiochus Soter across the empire as “kleroi”, military colonists. These formed the nucleus of the future army of the Seleucid Empire.

Thus perhaps more than any of the other Successor Kingdoms the Seleucid Royal Army traced its lineage and maintained the traditions of the army of Alexander and his immediate Successors (many of which were great military leaders in their own rights). This, combined with the vast financial resources of what had been the Persian Empire at their disposal, made the Seleucid army the largest, the most lavishly equipped, and (arguably) the most effective of the armies of the Successor kingdoms.

Our most complete information on the composition of the Seleucid Royal Army comes to us from Polybius, who chronicled events beginning with the accession of the Antiochus III (“The Great”), in 223 BC. Accounts of events prior to this are fragmentary, with large gaps in our record. But it is reasonable to suppose that the army that existed at the start of the reign of the sixth Seleucid King evolved from the army that had marched with Nicator and his rival Diadochii. Perhaps the best author on the subject of the Seleucid Army is B. Bar-Kochva. His work, the “The Seleucid Army: Organisation and Tactics in the Great Campaigns” (Cambridge Classical Studies), provides an in-depth analysis and a good working thesis. However, some of his conclusions are controversial and not accepted by all scholars as the final word on the subject.

Bar-Kochva argues that the Seleucid army was composed of three rough branches: The Royal Guard, which was the standing army; the “reservists” called up in time of emergency, drawn from the various military settlements dotting the empire, and comprising the largest of the three branches; and the various units of mercenaries.

Starting with the second and largest of the three branches, the reservists, helps to explain the other two.



Seleucus’s son and successor, Antiochus I Soter (“the Savior”) settled most of old and aging Royal Army he inherited from his father in various military colonies, or “kleroi”, scattered throughout the new empire. These soldier-settlers, called “kleruchs” (in Greek, klerouchos, meaning “lot holders”) or alternately “katakoi”, were Macedonians , Greeks and Thracians. These veterans were settled together in their regiments, maintaining their unit’s military traditions and legacy; something they managed to effectively pass down to their children and later generations of Seleucid soldiers.

They were granted farm plots within the colonies, in return for their and their descendants continuing military services when required. In practice, this meant that these settlements provided regiments for the Royal Army in time of war; each fighting in their traditional styles. The Macedonian settlers provided the manpower for the phalanx and some of the cavalry units. The Greeks and Thracians provided both light and heavy infantry and cavalry units.

Keeping to their military traditions, the Seleucid kleroi could provide units of “Cretan” archers; “Thracian” peltasts; “Macedonian” and “Greek” phalangites; “Macedonian” Companions and “Thessalian” cavalry. Of course, these soldiers were seldom of purely Hellenic heritage, but were instead of mixed-blood.

1375384 Marriage at Susa

Alexander had encouraged intermarriage between Hellenes and Asians; dramatically symbolized by the mass Marriage at Susa in which he and hundreds of his friends and officers took Persian brides in 324BC. Though many Macedonians put off these Persian wives after Alexander’s death, Seleucus himself honored his marriage to the noble Persian lady, Apama (daughter of Spitamenes, Alexander’s brave and effective opponent in Sogdiana); and she became the mother of his heir, Antiochus I. Thus even the Seleucid royal family was of mixed Macedonian and Iranian blood. However, the sons of such marriages were still considered “Macedonians” by the Seleucid sources.

As with all of the Successor states, the “Phalanx” was the heart-and-soul of the Seleucid army. From the kleruchs came the three divisions of the phalanx; named for their Diadochi-antecedents: the Argyraspides (“Silvershields”), Chalkaspides (“Brazenshields”), and the Chryaspides (“Goldenshields”). The first was the core of the Royal Guard, and will be discussed below; while the latter two were reserve formations only called up in time of emergency. Each of the two reserve divisions of the phalanx, the Chalkaspides and the Chryaspides were 8,000 – 10,000 strong.

1375389.jpgThe original phalanx of Philip and Alexander fought in a sixteen-rank deep formation; armed with a two-handed, 18 foot long pike called a sarissa. Originally made of cornel wood (according to Theophrastus; author Nicholas Sekunda makes a strong though not entirely convincing argument for Ash wood) and consisting of two equal pieces fitted together and joined by an iron tubular sleeve 61/2″ long. The phalanxes of later Successor State experimented on using longer sarissa; in the 3rd century some at least reaching an unwieldy 24′. However, 21′ became the norm by the end of that century, remaining so throughout the Hellenistic period.

Likewise, the depth of the phalanx grew in the Successor armies; with the Seleucid phalanx at the Battle of Magnesia, for example, deploying in 32 ranks. This was perhaps an attempt to put more weight behind the “push of pikes” when two opposing (Successor State) phalanxes met in battle. However, 16 ranks remained the norm. Phalanxes were also drilled so that they could change depth in battle; from 8 ranks to 16, and from 16 to 32. They could also form square when attacked from the flanks or rear.


The hard-charging horsemen who had leant Alexander’s army its striking power were likewise represented within the Seleucid kleroi.

The kleroi cavalry of the earlier Seleucid kings fought as lightly armored lancers or javelineers; in the traditions of Greece and Macedonia. These were drawn from men of the Macedonian and Greek (particularly Thessalian) settlements. Lydians and Medes, who had a heavy cavalry tradition of their own, were also recruited and fought in their native styles. However, by the middle of the reign of Antiochus III these “line” heavy cavalry were rearmed and armored as cataphracts. Heavily armored horsemen, riding fully or partially armored horses, were common among the nomadic hordes of the Eurasian steppes, and had been seen in the later Achaemenid Persian cavalry from the Upper Satrapies. As the Cappadocian and Lydian horse already fought in this style, at least some of the early Seleucid “line” cavalry from these regions may already have been cataphracts. Antiochus III had direct experience with these during his campaign to reestablish Seleucid rule over the Upper Satrapies (209-205 BC); and was impressed enough to make this the standard troop type for all Seleucid kleroi and native heavy horse regiments.

1375392.jpg Early Seleucid Anatolian armored cavalry, precursors to the Cataphracts.

The total number of “line” heavy/cataphract cavalry was about 6,000. These rode fully armored horses and the riders were armored in a combination of Iranian and Greek armor from head to toe. Their main weapon was the kontos, a heavy 12′ lance. These were shock cavalry, and their role in battle was to shatter opposing formations of horse and to menace the flank and rear of opposing phalanxes. They performed this mission brilliantly in their first engagement at Panium against the Ptolemies in 200 BC.

Light cavalry regiments, drawn from Thracian or Paionian settlers, were also seen in small number. The majority of light cavalry, though, were provided by the native tribes of Anatolia, Arabia, Iran and the Upper Satrapies of central Asia (more on these later).

The kleroi provided the Seleucid state with a true reserve army component. At little cost to the monarch, a large pool of trained and organized men could be maintained; and called up with little notice to “flesh-out” any field force. The number of such kleruch-soldiers available to the Seleucid state is speculative. But not less than 25,000 men could and were called up at various times from the ranks of the kleruchs; with another 12,000 of the settlers serving at any given time in the “standing army”, the Royal Guards.



The Seleucid kings maintained a standing body of troops in various regiments, collectively referred to in the sources as the Royal Guard.

The core unit of the Guard was the Argyraspides (“Silvershields”) division of the phalanx. Also referred to in the sources as “The Seleucid Royal Guard”, this phalanx was lavishly (and expensively) equipped from the royal arsenal at Apamea, in Syria; and numbered 10,000. Interestingly, this number is identical to that of the Persian Immortals, which played the same role in Achaemenid Persia.

This regiment traced its lineage to the famed Hypaspists of Philip and Alexander. In India, Alexander had granted this regiment ( then 3,000 strong) silver-faced shields. This elite foot guard regiment fought in the Wars of the Diadochi; first under Eumenes against Antigonas One-Eye, and then switched sides after the Battle of Gabiene. Antigonas posted them to the far eastern satrapy of Arachosia (western Afghanistan). It has been suggested that Seleucus revived the unit after taking control of Babylon and the eastern (“Upper”) satrapies (modern Afghanistan and Turkmenistan); using them as the cadre for his Foot Guard.

1375405.jpgThe Seleucid Argyraspides were phalangites, drawn from the mass of kleuch settlers. Bar-Kochva suggests that this was a kind of national service; that every kleroi had to send a young male family member to serve a term of service of several years in the Royal Guard. This would serve to bond them personally to their king and country and to give them regular military training and experience. They returned to the ranks of the reservists after their term in the Guard expired; to be reactivated in time of need as a member of one of the reserve divisions of the phalanx (the Chalkaspides or Chryaspides).

Within the organizational structure of the Argyraspides, Bar-Kochva argues, there existed a “special operations” battalion. These could be detached for special assignments (such as the nighttime escalade of Sardis in 214 BC); or, if needed, fight in the manner of the original Alexandrian “hypaspists”(elite, fast-moving armored spearmen) or “thorakitai” (armored peltasts). Within the original Hypaspists of Philip and Alexander there was an elite Guard battalion 1,000 strong called the Agema. It is possible that this special battalion within the Seleucid Argyraspides was the counterpart to the earlier Macedonian Agema of the hypaspists.


After their defeat by the Romans at Magnesia in 190 BC, a portion of the Royal Guard may have been reequipped and trained as “imitation Romans”. These presumably would have fought with large oval scutum, throwing spear (perhaps a version of the pilum) and short sword. In his depiction of the Parade at Daphne in 166 BC Polybius describes this unit, which he claims numbered 5,000. Bar Kochva suggests that after Magnesia and the rough handling the phalanx  received at the hands of the Romans, that half of the Argyraspides were so re-equipped and trained to fight in the Roman style. Bar Kochva suggests that the remainder of the Royal Guard retained their sarissa, fighting as phalangites.

The Royal Guard cavalry were organized into three elite regiments, two of which can be considered as true bodyguard units, who accompanied and guarded the king wherever he traveled and fought around him in battle. Each of these was 1,000 strong. Senior was the Agema (“Guards”). Dating back to when Seleucus Nicator ruled only the Eastern Iranian satrapies, these were recruited from the finest of the Medes, a race renowned for their skillful horsemanship. They were very heavily armored, fighting in battle as lance-armed semi-cataphracts; with at least the front-portion of their horses armored as well.

1375411.jpgThe second unit of the Horse Guards were the Hetairoi (“Companions”). Without doubt, this regiment traced its lineage to men who rode behind Alexander; and was recruited from amongst the Macedonian and Greek settlers of the empire. They were armed and fought in the same fashion as the Agema, though a bit lighter (one theory is that they wore cuirass, arm protection, and helmet, but no leg armor).

Finally, from the kleroi-town of Larissa in the trans-Jordan region, where had been settled men of the famed Thessalian horsemen who had ridden behind Alexander’s general, Parmenio, came the third regiment of the Seleucid elite cavalry: the Epilektoi (“Picked” or “Elite”). From at least the 6th century BC onward, the riders of the broad Thessalian plain were esteemed as the finest cavalry in Greece. In Alexander’s army, the Thessalian squadrons were second only to the Macedonian Companions. In the Seleucid army these fought as heavy, lance-armed cavalry (though lighter than either of the two guard cavalry units, or of the line cataphract regiments). When in the 2nd century BC Media had been lost to the Parthians this unit was collapsed into and became the Agema of the Guard. Like the other two regular units of the Guard, it was 1,000 strong.

The type horses used by the Seleucid heavy cavalry are unknown, but it can be assumed they were among the largest available to the Seleucid Empire. We know that in Media there was a royal herd of Nisean horse, the first great warhorse of world history. These horses were in great demand, used by the earlier Achaemenid Persian kings and by Alexander’s horsemen in the Indian Campaign. Is seems very likely that the Seleucids mounted their Agema and Hetairoi regiments on these large, swift chargers. There is also a 1,000 strong regiment called the Nisaioi in Polybius’ description of the Parade at Daphne in 166 BC. This may be a special unit of Medes mounted on Nisaian horses, or could be a mistake; referring to line cataphracts mounted on Nisaian chargers. As according to Diodorus (17.110.6) the Nisaian herd was as large as 60,000 horses it is entirely possible that all of the 9,000 Seleucid heavily armored cavalry (2,000 Guards, 6,000 Cataphracts and 1,000 of the mysterious Nisaioi) were mounted on Nisaian chargers.

The record of the Seleucid cavalry is very good. At Panium in 200 BC, the Seleucid cataphracts shattered their Ptolemaic opponents; then swung into the rear of the Ptolemaic phalanx, winning the battle. At Magnesia in 190 BC Antiochus III charged the Roman (or Allied) legion on the Roman left, at the head of the Agema, supported by another 3,000 Cataphracts. Bar-Kochva, working off of a passage from Justin, suggests that they shattered and broke through the Roman infantry, pursing them to the Roman camp. If true, this is one of the rare occasions in ancient history where cavalry were able to break through well-disciplined infantry.



The Royal Guard and reserve troops aside, the Seleucid monarchy made use of “specialty troops” and select mercenaries when necessary.

Most emblematic of all was the corps of war Elephants and the troops trained to support them.

Seleucus Nicator ceded the Macedonian territories in India (modern Pakistan) to the Indian ruler, Chandragupta the Maurya, in exchange for 500 elephants. In truth the number 500 is unlikely, but Seleucus did come west in 302 BC with an army whose main feature was a very large number of Elephants (Bar-Kochva thinks the number to be 150, as this was the size maintained by the later Seleucids in their Royal Herd).

At Ipsus the following year, these elephants played a key role in the defeat of Antigonas Monopthalmus (“One Eye”); by foiling the Antigonid cavalry under Demetrius from reentering the battle after breaking and pursuing Lysimachus’ horsemen.

1375537 Seleucid war elephant with guard, circa 165BC

Early in his reign the second Seleucid king Antiochus I Soter faced the invading Galatians in Phrygia. Most of the elephants of his father’s army had died or been taken by the usurper, Ptolemy Keraunos, to Macedonia. With only 16 beasts, Antiochus routed these Celtic invaders at the famous “Elephant Victory” in 273 BC. Thereafter the Seleucids attempted to maintain a breeding herd at Apamea, their military headquarters in central Syria. Antiochus III, who had just over 100 at the start of his reign, brought back an additional 150 beasts from his Eastern Campaigns.

By the end of his reign (if not earlier) Antiochus III’s  elephants were heavily armored, and mounted a howdah which carried a three-man crew: a pikeman, archer, and javelineer. He also attached small groups of archers and javelineers to support the elephants. But this was an ad hoc brigading of man and beast, and was found to be inadequate. Perhaps as a response to the disaster at Magnesia, where Roman javelineers and legionaries were able to get to close-quarters and wound the beasts, later Seleucid elephants were accompanied by a 50-60 man unit of “elephant guards”; attached directly to each beast and trained to fight around them. These were likely the troop-type called thureophoroi, spear-and-javelin armed medium-infantry equipped with helmet and a light oval shield, known as a thereos; or thorakitai, similar troops equipped with cuirass and greaves as well as helmet.

Seleucid elephants were of the Indian variety, unlike those used by both Ptolemaic Egypt and the Carthaginians, which were the smaller (now extinct) North African Forest species. The larger Indian elephants were capable of carrying a bigger howdah (three-man crew as opposed to two for the Ptolemaic elephants) and being heavily armored (which neither of their rival’s elephants were). At the Battle of Raphia (217 BC) the larger Seleucid elephants were able to push back and roughly handle their Ptolemaic opposites.

1375542 Excellent illustration of a duel between Seleucid (R) and Ptolemaic (L) elephants. Note the two-man crew of the Ptolemaic elephant, as opposed to the three-man crew of the larger Seleucid Indian elephant. (This illustration seems to depict the Ptolemaic elephant as one of the larger African Bush Elephants instead of the small, now extinct North African Forrest Elephant; used by Ptolemaic and Carthaginian armies.

The elephants had a mixed history of success and failure; though the reliance placed upon them by many ancient armies (including the Seleucids) suggests they were considered an successful and much-prized weapon. The fear in which the Romans held them is demonstrated by their demands that the Seleucids destroy their herd after Magnesia; a term of the Treaty of Apamea observed in the breach! The Roman Senate even sent a special envoy, Gnaeus Octavius, in 162 BC to destroy the elephant herd at Apamea, following the death of Antiochus IV Epiphanes. However, even after this event elephants are found in Seleucid armies on campaign, most notably during the wars in Judea against the Maccabees.

Another “specialty” troop type was the scythe chariot corps. How many such chariots were maintained is unknown; but they were a small force and of questionable value. Their use at Magnesia was disastrous, and contributed to the Seleucid defeat in that battle.

1375544.jpgMercenaries were a common feature of all Hellenistic armies, and the Seleucids were no exception. Mercenaries provided the static garrisons for vital fortresses, towns, and cities. They were, however, a tiny proportion of Seleucid field forces (unlike in the Ptolemaic armies).

The exception to this was the ferocious Galatians of central Anatolia, hired by Antiochus Hierax in great numbers during The Brother’s War in the mid-3rd century. They were, in fact, the bulk of the forces he used against his brother, Seleucus II. Galatians fought both as heavy and light infantry and cavalry, and were known for their furious courage in battle.

Cretan mercenaries were highly prized by the Seleucid kings (as they were in the army of Alexander the Great), and were considered the best archers in the Mediterranean world. Unlike the native archers of Syria or Persia available to the Seleucids, Cretans were more than ready to fight at close quarters with small axe, sword or knife when required.

1375545.jpgDuring the early years of the reign of Demetrius II (circa 147 BC) the king was dominated by (and a virtual puppet of) the captain of his Cretan mercenaries, the former pirate Lasthenes. For five years the mercenaries terrorized and looted the country (“The Cretan Terror”). The citizens of Antioch rose in a doomed attempt to throw out the foreigners. In bloody street fighting thousands of Antiochenes were killed by the Cretan (and Jewish) mercenaries. Much of the city was destroyed, and the Cretans took reprisals against all who had resisted them.

However, Lasthenes overreached in the end : He attempted to disband the regular and reserve troops of the army. This led to a revolt by the general Diodotus Tryphon; who, with the support of many units, raised the infant son of a former king, Alexander Balas, to the throne. Demetrius and his Cretans were thrown-out of Antioch; Demetrius going east to fight the Parthians, the mercenaries departing the country.

The Cretan Terror showed the Seleucids what others were to learn throughout history: mercenaries in small numbers make good servants; but when in the majority make a bad and dangerous master!

As noted above, Judean mercenaries were also used and much prized, by both the Ptolemies and the Seleucids. This was at least in part due to the notable lack of love the Jews had for the local (Gentile) populations of these kingdoms. Their loyalty was strictly to their paymaster, and they had no compunction in using brutal force against the civilian population if called upon to crush dissent. Judeans fought as slingers and thureophoroi, and had a doughty reputation as fierce fighters.

Following the rising of the citizens of Antioch against the Cretans, and the subsequent sack of the city by the mercenaries, the Judean mercenaries carried a vast fortune in loot back to Judea. When the Maccabee revolt broke out a few years later, it may well have been (in part) inspired by the weakness these returned Judean mercenaries related concerning the decayed state of their Seleucid masters. Their service as mercenaries in Ptolemaic and Seleucid service gave many Jews the necessary military experience and knowledge of Hellenistic methods to fight and, at times, defeat the forces the Seleucid government sent against them.

1375546.jpgLight infantry and cavalry were often recruited from the frontiers of the Empire. Arab dromedary troops, Saka horse archers, fierce javelineers from the southern mountains of Anatolia (Psidians and Lycians), and many other wild tribesmen from the untamed regions of the vast Empire were employed for various campaigns by the Seleucid kings in their long history.


The Seleucid army was (arguably) the best and certainly the largest of the Successor Kingdoms. But it had defensive commitments spanning the Near East: from the Aegean Sea to the banks of the Jaxartes River, in modern Turkmenistan. They were surrounded by powerful neighbors and rivals, and the first call of every Seleucid king was to lead the army in the defense of the vast Seleucid patrimony. The doom that eventually overcame their Empire was largely due to the vast sprawling geography of their realm; and the failure of the Seleucid dynasty to fully mobilize the military potential of their native subjects. Their rule and their army was based solidly upon the Macedonian and Greek settlers of their Empire.

In battle, the Seleucids knew success and failure. The army evolved over time in response both to these defeats and the lessons learned; and in response to evolving threats. Its record, on the balance, is quite impressive.

Ultimately, it was the Romans and the Parthians who divided-up the Seleucid kingdom between them; then fought each other for centuries over the disputed border regions.




Some of the artwork in this article has been reproduced with the permission of Osprey Publishing, and is © Osprey Publishing, part of Bloomsbury Publishing Plc.

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  1. ritaroberts says:

    What a fascinating post, I enjoyed every minute of it. !!!

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  6. Paul says:

    This is a wonderfully written and highly accessible article, thank you so much!

    I was curious if you know of any Indians serving in any of the Successor armies (particularly in roles of the Elephant ‘corps’)?

    I have seen depictions through several media (modern art, modelling etc) of distintively Indian ‘looking’ mahouts, for example.

    Thanks agin for a brilliant article!

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