The phalanx was a large, dense formation of men armed with small shields and a long pike called the sarissa.
This form of fighting had been developed by the Macedonian army in the reign of Philip II of Macedon and his son Alexander the Great.
The distance from Greece put a strain on the Seleucid military system, as it was primarily based around the recruitment of Greeks as the key segment of the army.
[4] These Greek settlers would be used to form the Seleucid phalanx and cavalry units, with picked men put into the kingdom's guards regiments.
[13] Secondly, the future wars that the Seleucids might be fighting would probably be in the eastern satrapies against mobile enemies and other large areas of land.
[14] Thirdly, the defeat of the Antigonids at the Battle of Pydna in 168 BC was a great culture shock, showing the complete destruction of the Macedonian military system at the hands of the Roman legion.
[14] The true extent of the adoption of Roman techniques is unknown, some have suggested that the infantry are in fact more likely to be Thureophoroi or Thorakitai, troops armed with an oval shield of the Celtic type, a thrusting spear and javelins.
Polybius's account of the Daphne parade is again the main source, but unfortunately the suriving fragment is only in a single manuscript and bears signs of a miscopying or lacuna.
The best guess at what the original sentence was by Georg Kaibel was that there were 20,000 Macedonians, divided into 10,000 chrysaspides (Greek: Χρυσάσπιδες 'Golden-Shields'), 5,000 chalkaspides, and the rest (the other 5,000) agryaspides.
We do not find the militias involved in the great campaigns before the general decline of the kingdom, which occurred in the latter half of the second century BC.
Demetrius, having taken the throne, decided to disband the majority of the regular army and reduce its pay by a large amount.
[17] Due to the lack of Greeks in the lands of the Seleucid kingdom, the use of allied, vassal and mercenary troops was great.
For example, Thracian mercenaries along with Mysian, Cilician, Lycian, and Vassal troops from the mountainous areas of the empire were used by Antiochus III in conjunction with Thorakitai in his storming of the Elburz range in 210 BC.
For example, the arms and equipment of the Thracian troops allowed the individual soldier greater mobility and freer action in hand-to-hand combat than a phalangite could adopt.
[25] Unlike the more westerly powers, like the Romans and other Greek states, where infantry dominated the battlefield, in the 'vast spaces to the east, the horse cultures were more influential'.
The eastern style of horse warfare would have a deep impact in the reign of Antiochus III, when he armed his heavy cavalry along Parthian lines.
However, unfortunately for the Seleucids, their main rivals, the Romans and Ptolemies, used armies that were centered around a core of good infantry.
The lancers, who performed the job of heavy cavalry before the Cataphract, were known by numerous names, for example dorataphoroi, sarissaphoroi, kontophoroi, xystophoroi and lonchophoroi.
[29] The light cavalry was used to skirmish, so troops such as those that fought in the Tarentine style were common within this category, although there were numerous native contingents too.
The Hetairoi were recruited from the younger generation of military settlers and acted as the standing guard cavalry unit of the army, serving in peace and in war.
The desire to meet the phalanx head on and the need for protection was remedied after the anabasis of Antiochus III to the eastern satrapies in 210-206 BC.
At this time, Antiochus came into contact with the Parthian cavalry, of which some were heavily armed with scale armour for both the rider and horse and longer lances known as a kontos.
[30] Camels are attested in use in the Seleucid army at the battle of Magnesia, but their small number (500) suggests they were not a regular addition.
The Roman senate supported the young and weak Antiochus V over the stronger and more capable Demetrius, who was a hostage in Rome at the time.
There was a moment of success and strength with the Parthian campaign of Antiochus VII, but his death in battle led to further defeat and decline.
The loss of manpower and political instability may well have ensured that the Seleucid army was dependent on mercenaries and citizen militias and unable to maintain a phalanx of the size seen at Raphia and Magnesia.