Seleucid army The Seleucid army was the army of the Seleucid Empire , one of the numerous Hellenistic states that emerged after the death of Alexander the Great . As with the other major Hellenistic armies , the Seleucid army fought primarily in the Graeco - Macedonian style , with its main body being the phalanx . The phalanx was a large , dense formation of men armed with small shields and a long pike called " 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 . Alongside the phalanx , the Seleucid armies used a great deal of native and mercenary troops to supplement their Greek forces , which were limited due to the distance from the Seleucid rulers ' Macedonian homeland . Manpower . 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 . In order to increase the population of Greeks in their kingdom the Seleucid rulers created military settlements . There were two main periods in the establishment of settlements , firstly under Seleucus I and Antiochus I and then under Antiochus IV . The military settlers were given land , " varying in size according to rank and arm of service ' . They were settled in ' colonies of an urban character , which at some point could acquire the status of a polis " . Unlike the Ptolemaic military settlers , who were known as " Kleruchoi " , the Seleucid settlers were called " Katoikoi " . The settlers would maintain the land as their own and in return they would serve in the Seleucid army when called . The majority of settlements were concentrated in Lydia , northern Syria , the upper Euphrates and Media . The Greeks were dominant in Lydia , Phrygia and Syria . For example Antiochus III brought Greeks from Euboea , Crete and Aetolia and settled them in Antioch . These settlers would be used to form up the Seleucid phalanx and cavalry units , with picked men put into the guards regiments of the kingdom . The rest of the Seleucid army would consist of a large number of native and mercenary troops . These troops would serve as light auxiliary troops . However by the Daphne Parade of 166 BC the large amount of ethnic contingents were missing from the army of Antiochus IV . This was most likely due to the reform of the army that was undertaken by Antiochus IV . In his reign Antiochus IV had built 15 new cities " and their association with the increased phalanx . . . at Daphne is too obvious to be ignored " . Infantry . Argyraspides . The principle guard infantry unit of the Seleucid army was the ' Silver - Shields ' , or Argyraspides . They were a permanently embodied guard unit which was formed from the sons of military settlers . They were armed in the Macedonian manner with a sarissa and fought in the phalanx formation , much like the other Hellenistic armies of the time . The Argyraspides were probably a corps of about 10 , 000 men who were picked from the entire kingdom to serve in this unit . The whole kingdom may mean ' regions like Syria and Mesopotamia , which were the nucleus of the Seleucid Kingdom , there was a greater density of Greek soldiers ' . ' Romanized ' infantry . In 166 BC , at the Daphne Parade under Antiochus IV , the Argyraspides corps is only seen to be 5 , 000 strong . However 5 , 000 troops armed in the Roman fashion are present and they are described as being in the prime of their life , perhaps denoting their elite nature . It is possible that the missing 5 , 000 men of the Argyraspides were the 5 , 000 ' Romanized ' infantry marching alongside them . The training of a segment of the royal guard in " Roman ' methods was probably down to several factors . Firstly Antiochus IV had ' spent part of his early life in Rome and had acquired rather an excessive admiration for Rome ' s power and methods " . 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 . Training troops in this way would add to the overall efficiency and capability of the army and make it more manoeuvrable . Indeed the ' Romanized ' troops are seen facing the Maccabees at the Battle of Beth Zechariah in 162 BC . 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 . It has been suggested that the fact that these 5 , 000 men are marching at the head of the army was meant to show Antiochus IV ' s intention of reforming the entire Seleucid army along Roman lines , though whether or not this complete reform actually took place is unknown . 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 . Chrysaspides and Chalkaspides . The majority of the Seleucid phalanx was probably two corps that we find are mentioned in the Daphne Parade of 166 BC . 10 , 000 Chrysaspides ( ' Golden - Shields ' ) and 5 , 000 Chalkaspides ( ' Bronze - Shields ' ) are seen at Daphne . Little else is known specifically about them although they may have been present at the battle of Beth - Zachariah in 162 . Citizen Militia . There was a militia , at least in Syria . They were from the Greek cities who had no specific role within the regular army . We do not find the militia ' s involved in the great campaigns before the general decline of the kingdom which occurred in the latter half of the second century BC . By then the many important military settlements had fallen to Pergamon and the Parthia . In 148 BC at the Battle of Azotos against the Maccabees the Seleucid army was called the ' Power of the Cities ' , probably owing to the high proportion of citizen militia mobilized from the coastal cities . Citizens of Antioch played a major role in the overthrowing of Demetrius II Nicator . Demetrius , having taken the throne decided to disband the majority of the regular army and reduce its pay by a large amount . In place of the regular army Demetrius ' power rested with his Greek , especially Cretan , mercenaries in what was known as the ' Cretan Tyranny ' . Not long after Azotos the majority of the citizen militia were wiped out in Antiochus VII ' s disastrous Parthian War of 129 BC . The militia were most likely armed and fought in the style of the Thureophoroi . Allied , Vassal and Mercenary Infantry . Due to the lack of Greeks in the lands of the Seleucid kingdom the use of allied , vassal and mercenary troops was great . They were often used as light and auxiliary troops , supplementing the phalanx and cavalry . Large amounts of native contingents fought at the Battle of Raphia in 217 BC . Among them were 10 , 000 Arab infantry , 5 , 000 Dahai , Carmanians and Cilicians . Certain ethnic contingents , be they vassal or mercenary were of considerable use in certain situations . For example Thracian mercenaries along with Mysian , Cilician , Lycian and Mysian troops were very efficient at fighting in rough terrain and mountainous areas . For example 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 . The Persian and Iranian troops were most likely of a higher professional military standing than most of the other contingents as they are seen on garrison duty throughout the empire . In the review at Daphne in 166 BC the large amounts of allied and vassal contingents are missing . They were of doubtful reliability , usefulness and efficiency . So much so that Appian blamed them for the defeat at the Battle of Magnesia in 190 BC . The absence of auxiliaries from the army of Antiochus IV may have contributed to its strength . Making up for the loss of ethnic contingents the army was supplemented by mercenaries , who were more experienced and better trained . The Thracian and Galatian mercenaries at Daphne would have been of good use in campaigns in the rough , hilly terrain . For example the arms and equipment of the Thracian troops allowed for the individual soldier greater mobility and freer action in hand - to - hand combat that a phalangite could not take part in . Cavalry . 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 ' . Speed and mobility were the key , especially when dealing with foes like the Parthians and the Graeco - Bactrians . The Parthian style of warfare was based around heavily armoured cavalrymen , Cataphracts , and horse archers which were used in hit and run style tactics . 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 which centered around a core of good infantry . In this sense there was a sense of the overvaluing of cavalry as an offensive arm . Antiochus III was an excellent cavalry commander , his assault at Tapuria in 208 BC as described by Polybius could almost act as a ' military treatise on how to conduct a cavalry battle ' . However Antiochus III was not as apt when dealing with infantry , be it Greek or Roman . At Magnesia Antiochus ' disregard for his phalanx and his misdirected cavalry charge led to his defeat . The Seleucid cavalry , after the introduction of the Cataphract , can be sub - divided into several categories . Firstly there were the heavy cavalry of which there were Kataphraktoi ( armoured ) and Aphraktoi ( unarmoured ) . The Aphraktoi were divided into 2 groups , lancer and missile troops . 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 . Xystophoroi and lonchophoroi were mentioned specifically by Titus Flamininus whilst in discussion with the Achaeans . 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 . Agema , Hetairoi and Nisaioi . Along with the guard infantry unit , there were two guard cavalry regiments , each 1 , 000 strong . These were the Agema ( the ' Guards ' ) and the Hetairoi ( ' Companions ' ) . 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 . However it seems that writers referred to them by several names other than just the ' companions ' ; the basilike ile ( ' royal squadron ' or ' regia ala ' according to Livy ) , and the hippos hetairike ( ' horse companions ' ) . Bar - Kochva presumes that from this their full title may well have been the ' royal ala of the companions ' . The Agema ' consisted of Medes , selected men , with a mixture of horsemen of many races from the same part of the world . Both corps of cavalry could escort the king into battle , or both could be brigaded together into one unit of 2 , 000 . Both units were armed with a xyston , a cavalry lance not so dissimilar to the sarissa . They were also equipped with a cuirass and helmet . After the introduction of the Cataphract the Hetairoi were given similar but lighter protection . As for the Agema , they probably were similarly equipped to the cataphracts themselves . Another regiment of horse , similarly armed to the cataphracts , were the Nisian cavalry ( Nisaioi ) composed of Iranians . Epilektoi . At the Daphne parade there was also a regiment of ' picked ' , known as Epilektoi , horse , numbering 1 , 000 . The Epilektoi were most likely recruited from the city of Larissa , which was founded by colonists from Larissa on the Greek mainland . After the loss of Media , main recruiting ground for the Agema , to the Parthians the Epilektoi were given the title and role of the Agema by Alexander Balas . Kataphraktoi . Despite the prospect of a mobile cavalry phalanx the cavalry still faced problems . The xyston was still too short to meet the sarissa phalanx head on . The weight of their armour restricted movement , but the elimination of a shield for protection made the rider and horse more vulnerable . 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 . The kontos ' almost equalled the phalangite sarissa ' . The cataphract had numerous advantages though . First , their armour provided protection from missiles , arrows , spears and pikes . Second , the kontos allowed them to block an enemy advance and attack from further away . For example , the Seleucid cataphracts were able to beat the Ptolemaic cavalry and attack their phalanx at Panium in 200 BC with relative ease . Nevertheless , they still had their problems . Like the phalanx , an attack on their flank could prove fatal for the rider and these difficulties were exploited by infantry ' which assaulted the cataphracts from the flanks , attacking body parts of the riders and horses that were unprotected by armour ' . The cataphracts could also have their kontos grabbed from them or be knocked off their horse . In order to remedy this , semi - heavy cavalry were needed to watch their flanks . Politikoi . Along with the citizen militia infantry there were also cavalry regiments of militia from the cities , known as Politikoi . The citizen cavalry was recruited from the richest citizens of the cities who did not hold the legal status of ' Macedonians ' . Citizen cavalry of this sort are seen at the Daphne parade and , in this case , probably from Antioch and not collected from all the coastal cities . The Politikoi were probably not a unitary regiment of horse , but a collection of separate squadrons with each squadron having its own distinctive dress and equipment . Decline . Despite numerous advantages that the Seleucid had at the height of their power the empire soon began to fall into decline , especially with the coming of so many dynastic wars between the rival claimants to the Seleucid throne . The Romans , increasingly after the death of Antiochus IV , supported those claimants who they felt would be weak and no threat to them . 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 . When Demetrius took the throne as Demetrius I Rome further undermined him by supporting Alexander Balas and numerous rebel groups such as those of John Hyrcanus in Judea . The ever weakening empire led to the Parthians to sweep into their eastern satrapies and take them . These conquests took place at the same time as the bitter civil wars in the empire . 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 these territories meant the loss of vital economic and manpower resources . By the beginning of the 1st Century BC the Seleucid kingdom was still troubled by instability caused by civil war between the northern and southern branches of the Seleucid royal household . The loss of manpower and political instability may well have ensured that the Seleucid army was dependent on mercenaries and citizen militia ' s and unable to maintain a phalanx of the size seen at Raphia and Magnesia .