The Hellenistic armies is a term that refers to the various armies of the successor kingdoms to the Hellenistic period, emerging soon after the death of Alexander the Great in 323 BC, when the Macedonian empire was split between his successors, known as the Diadochi ().
Initially, the Hellenistic armies were very similar to those commanded by Alexander the Great, but during the era of the Epigonoi (Ἐπίγονοι, "Successors") the differences became obvious, with the Diadochi growing to favor large masses of soldiers rather than smaller, well-trained ones, and weight was valued over maneuverability. The limited availability of Greek conscripts in the east led to an increasing dependence on mercenary forces, whereas the Hellenistic armies in the west were continuously involved in wars, which soon exhausted local manpower, paving the way for Roman supremacy in the region.
Three major Hellenistic states were the Seleucid Empire, the Ptolemaic kingdom and Macedon under the Antigonid dynasty. Other Hellenistic states were Epirus under Pyrrhus, the Kingdom of Lysimachus, the Kingdom of Pergamum, the Kingdom of Pontus, the Greco-Bactrian Kingdom and Indo-Greek Kingdom, the Achaean League and the Aetolian League, and the city states of Rhodes, Sparta, Syracuse, Athens, and others.
Numerical strength
The Diadochi were capable of deploying some of the largest armies of their day, and could easily outmatch the numerical strength of either Phillip's or Alexander's full strength contingents. However, the size of the armies participating in different campaigns could vary extremely, from a few thousand to over 70,000 soldiers. Of these armies, outside Greece, only a fraction would have been of Greek origin, the rest being allied contingents and conscripts from the local population.
Manpower and the state
Lack of manpower was a serious concern for many Hellenistic rulers. The disparity between the manpower reserves available to Rome and to any other Hellenistic monarch had a profound influence on the way in which the opponents made war.Sabin & van Wees & Whitby (eds.) (2007), The Cambridge History of Greek and Roman Warfare: Volume 1, p. 336 Roman generals could more easily risk defeat in battle, while for Hellenistic generals, a defeat might cripple their manpower base for nearly a generation. Many states had to rely on mercenaries to bulk up their citizen forces: For example, the army of the Achaean League under Aratus of Sicyon was re-organized to contain a permanent corps of mercenaries that numbered 8,000 foot soldiers and 500 on horseback, compared with the corps of picked Achaean troops, which numbered only 3,000 foot and 500 horse.F.W. Walbank (1933), Aratos of Sicyon
To take another example, by the mid-third century BC, the Spartan citizen population had decreased to a tiny fraction of what it had been at the time of the Persian Wars (Cleomenes' army could only field about 5,000 menG.T. Griffith (1935), The Mercenaries of the Hellenistic World). The inchoate reforms of Agis IV around 240 BC had failed after a reaction by those opposed to the reforms. The problem of the lack of man-at-arms was then taken up by Cleomenes III of Sparta, who attempted to address it by his radical reforms. Cleomenes III launched a coup against his rivals at home and used their demise to push forward a reform to increase Spartan manpower. In 227 BC, Cleomenes cancelled all debts, pooled and divided the large estates and increased the citizen body by enfranchising 5,000 Perioikoi and 'metics' (resident foreigners). Before long, he increased the citizen body further by allowing Helots to buy their freedom for five minae and therefore he "acquired 500 talents, some of which he used to arm 2,000 men in the Macedonian fashion as phalangites".N.G.L. Hammond & F.W. Walbank (1988), A History of Macedonia, Volume III, 336-167 BC, p. 356 However, the defeat at Sellasia in 222 BC and the attendant great loss of manpower forced a reliance on mercenary soldiers, who were the basis of power for Machanidas and Nabis, his successors.
The extreme losses affected Philip V of Macedon greatly, especially after his defeat at the Battle of Cynoscephalae in 197 BC. With such a small population, and such drastic losses in battle, the Antigonid king had to think radically as to how to improve his nation's performance in the next war. In between the Second and Third Macedonian Wars, Philip V embarked on a major reform and re-organization of the kingdom. Expansion could secure "the great reservoir of available man-power"F.W. Walbank (1940), Philip V of Macedon that lay north in Thrace. Philip then transported segments of the populations of the coastal cities to the northern frontiers and moved those Thracians south. This, combined with economic and political moves, re-built Macedonia and allowed for Perseus, Philip's successor, to be in a stronger position. Perseus had enough grain to last the army ten years - without drawing on harvests - enough money to hire 10,000 mercenaries for ten years, and field an army of 43,000 soldiers, a significant improvement compared to the situation of Philip V at Cynoscephalae in 197 BC, who fielded an army of 25,500 men.F.W. Walbank (1940), Philip V of Macedon, p. 256
The eastern kingdoms of the Ptolemaic, Seleucid, Graeco-Bactrian and Indo Greek kingdoms, had an even more problematic situation. The basis of their militaries relied on Greeks, which were not common to the areas that they ruled over. In order to overcome this, these kingdoms set up military colonies, known as Klerouchoi, to settle mercenaries and others from Greece. The system would allow for the colonists to be given a plot of land and in return they would provide military service when needed. In Ptolemaic Egypt, for example, soldiers and officers were given rewards "In exchange for military service, whenever needed."Angelos Chaniotis (2005), War in the Hellenistic World, p. 85 W.W. Tarn even suggests that the Greek (known to the Indians as "Yavanas") population in India may not have been as small as one would suppose, stating "There may well have been many more Yavanas...than we should suppose; we may have to reckon with a considerable number of men, adventurers or mercenaries from the west."W.W. Tarn (1980), The Greeks in Bactria and India, p. 251
Typical units and formations
Hellenistic infantry
The Phalanx
The Hellenistic armies based their strength on the pike-bearing phalanx, the legacy of Philip II and Alexander the Great. Throughout the age of the Diadochi and the Epigonoi, the phalanx, as the line of the pikemen was commonly referred to by ancient authors, remained the backbone of armies as diverse as those of Seleucus I Nicator, Pyrrhus of Epirus, Antiochos III and Philip V. The phalanx was an infantry formation, characterized by dense ranks and pikes (sarissas). Their soldiers (known as phalangites) ranged from professional warriors, drilled in tactics, weapon use and formation, typically of Greek origin; to trained, non-Greek villagers, as was the case in the army of Ptolemy Philopator, the victor of Raphia. Certain reforms in the weight of the phalangite equipment and the conscription methods used turned the phalanx from a maneuverable formation into a bulky, slow-moving steam roller, whose charge no enemy was able to withstand. Maneuvers like the fake retreat of Phillip II at Chaeronea or the oblique advance of Alexander at Arbela were never again attempted, but, as long as the phalanx remained on relatively level terrain and its flanks were kept secure, it was not conquered by any other formation. Although it has been argued that the role of the phalanx on the battlefield was to act as an anchor for the entire army, holding the enemy in place, pushing him back, exerting a heavy toll on enemy morale, while the cavalry struck the enemy flanks and delivered the fatal blow to cripple their opponents, in most battles it was used as the main weapon to achieve victory.
Equipment varied over the years, and was also dependent on the geographical region, the preference/wealth of the ruler, and the assets of the individual soldier.
Helmets ranged from simple, open-faced affairs to stylized Thracian models (complete with mask-like cheek protectors that often imitated a human face). Historians argue about how common body armor would have been among phalangites, especially those in the middle ranks, but when it was worn it ranged from a cuirass of hardened linen (the linothorax), that may or may not have been reinforced/decorated with metal scales to metallic (typically bronze) breastplates.
The phalangite's shield - long misconstrued thanks to its description as a "buckler" by several writers - was a -diameter affair and less concave than the hoplite's aspis. It was secured by both a shoulder harness and a forearm brace, allowing the off-hand to release the hand grip and make wielding the enormous sarissa pike possible. Metallic greaves were also worn to cover the shins of the soldiers as they stood their ground, especially by the front and rear-most ranks.
The primary weapon of the phalangite was the sarissa, a massive spear that ranged from 16 feet (mid-late 4th century BC) to as much as 22 feet (near the nadir of the phalanx's development). First made famous by Philip of Macedon, it allowed Macedonian infantry to "outrange" the opposition's existing spear formations by several feet. The sarissa would have been largely useless in single combat, but a compact, forward-facing infantry formation employing it would have been almost impossible to challenge. The first five ranks of the phalanx would have their sarissa projecting horizontally to face the enemy, with the remaining ranks angling theirs in a serried fashion, often leaning against their fellows' backs. If front-rankers were killed, those behind would lower their spears and step forward to maintain a solid frontline.
In the event of close combat, or in circumstances where the sarissa was impractical, a variety of swords were employed - the classic xiphos, the kopis and the makhaira, for example. Any sword-fighting in the vicinity of the phalanx's front was complicated by the sarissa projecting from the 2nd-5th ranks around the 1st rank combatants.
The primary drawback of the phalanx was its vulnerability to attacks from the rear and flanks. This is the reason why it depended on the units on its flanks to at least hold off the enemy until he would naturally break from the phalanx's irresistible pressure. It also had a tendency to fracture, when led across broken terrain for extended periods in close-ordered battle formation. The Romans would later be able to use this weakness against the phalanx as their more mobile maniples could withstand the pressure of the phalanx longer than more traditional formations, thus earning valuable time for their wings to outflank it, as at Cynoscephalae and Magnesia, or for the phalanx to lose its cohesion due to prolonged movement forward or advancement through unfavorable terrain, as at Pydna. Yet, regardless of the many Roman victories against the Hellenistic Kingdoms, the legion never won against a phalanx by frontal assault. Even at Pydna, it took the strange withdrawal of the Macedonian cavalry for the Romans to finally outflank the phalanx and claim a costly victory.
As the reign of the Diadochi persisted from the late 4th century to the mid-first century BC, they grew to rely more and more on an increasingly heavier and longer-speared phalanx to ensure victory. Complementary arms of the later Hellenistic armies were neglected, fell into disuse, or became the province of unreliable mercenaries and subject peoples. Sound and creative tactics became increasingly rare as a result.