East Roman army The East Roman army refers to the army of the Eastern section of the Roman Empire , from the empire ' s definitive split in 395 AD to the army ' s reorganization by themes after the permanent loss of Syria , Palestine and Egypt to the Arabs in the 7th century during the Byzantine - Arab Wars . The " East Roman army " is the continuation of the Late Roman army of the 4th century until the Byzantine army of the 7th century onwards . The East Roman army was a direct continuation of the eastern portion of the late Roman army , from before the division of the empire . The east Roman army started with the same basic organization as the late Roman army and its West Roman counterpart , but between the 5th and 7th centuries , the cavalry grew more important , the field armies took on more tasks , and the border armies were transformed into local militias . In the 6th century , the emperor Justinian I , who reigned from 527 to 565 , sent much of the East Roman army to try to reconquer the former West Roman empire . In these wars , the East Roman empire reconquered parts of North Africa from the Vandal kingdom and Italy from the Ostrogothic kingdom , as well as parts of southern Spain . In the 7th century , the emperor Heraclius led the east Roman army against the Sassanid empire , temporarily regaining Egypt and Syria , and then against the Rashidun Caliphate . His defeat at the Battle of Yarmuk would lead to the Islamic conquest of Syria and Egypt , and would force the reorganization of the East Roman army , leading to the thematic system of later Byzantine armies . Sources . Much of our evidence for the East Roman army ' s deployments at the end of the 4th century is contained in a single document , the " Notitia Dignitatum " , compiled c . 395 - 420 , a manual of all late Roman public offices , military and civil . The main deficiency with the " Notitia " is that it lacks any personnel figures so as to render estimates of army size impossible . However , the " Notitia " remains the central source on the late Army ' s structure due to the dearth of other evidence . The Strategikon of the Emperor Maurikios , from the end of the 6th century , describes the cavalry tactics , organization , and equipment of the East Roman army towards the end of this period . The De re Militari of Vegetius , probably from the beginning of the 5th century , calls for reform of the West Roman army , which was similar to the east Roman army . However , the De re Militari emphasizes the revival of earlier Roman practices , and does not provide a clear view of the tactics , organization , and practices of any branch of the late Roman army . The histories of Ammianus Marcellinus provide a glimpse of the late Roman army before the division of the Roman empire . Those of Procopius , especially his Wars and parts of his Buildings , written while accompanying the magister militum Belisarius during the emperor Justinian ' s wars against the Sassanid empire and the barbarian successor kingdoms , provide a view of the east Roman army in the period , and its campaigns . The histories of Agathias and Menander continue those of Procopius . Another major source for the East Roman army includes the legal codes published in the East Roman empire in the 5th and 6th centuries : the Theodosian code ( 438 ) and the " Corpus Iuris Civilis " ( 528 - 39 ) . These compilations of Roman laws dating from the 4th century contain numerous imperial decrees relating to the regulation and administration of the late army . Origins and History . In 395 , the death of the last sole Roman emperor , Theodosius I ( r . 379 - 95 ) , led to the final split of the empire into two political entities , the West ( " Occidentale " ) and the East ( " Orientale " ) . The system of dual emperors ( called " Augusti " after the founder of the empire , Augustus ) had been instituted a century earlier by the great reforming emperor Diocletian ( r . 284 - 305 ) . But it had never been envisaged as a political separation , purely as an administrative and military convenience . Decrees issued by either emperor were valid in both halves and the successor of each " Augustus " required the recognition of the other . The empire was reunited under one emperor under Constantine I , after 324 , under Constantius II , after 353 , under Julian , after 361 , and and Theodosius himself , after 394 . The division into two sections recognized a growing cultural divergence . The common language of the East had always been Greek , while that of the West was Latin . This was not " per se " a significant division , as the empire had long been a fusion of Greek and Roman cultures ( classical civilisation ) and the Roman ruling class was entirely bilingual . But the rise of Christianity strained that unity , as the cult was always much more widespread in the East than in the West , which was still largely pagan in 395 . Constantine ' s massive reconstruction of the city of Byzantium into Constantinople , a second capital to rival Rome , led to the establishment of a separate eastern court and bureaucracy . Finally , the political split became complete with the collapse of the Western empire in the early 5th century and its replacement by a number of barbarian Germanic kingdoms . The Western army was dissolved and was incorporated into the barbarian kingdoms . The Eastern empire and army , on the other hand , continued with gradual changes until the Persian and later Arab invasions in the 7th century . These deprived the East Roman empire of its dominions in the Middle East and North Africa , especially Egypt . Army Size . Warren Treadgold estimates that the east Roman army had about 3 , 500 " scolae " or guards , 104 , 000 field army soldiers , with an uncertain number of sailors , and 195 , 500 border army soldiers , again with an uncertain number of sailors , in 395 . Treadgold also estimates that the east Roman army had about 150 , 000 field army soldiers , with an uncertain number of sailors , in 559 , late in the period of Justinian . Treadgold also estimates that the east Roman army had about 80 , 000 field army soldiers , with an uncertain number of sailors , in 641 , after the Islamic conquest of Syria and Egypt . Numbers . The size of the Eastern army in 395 is controversial because the size of individual regiments is not known with any certainty . Plausible estimates of the size of the whole 4th - century army ( excluding fleets ) range from c . 400 , 000 to c . 600 , 000 . This would place the Eastern army in the rough range 200 , 000 to 300 , 000 , since the army of each division of the empire was roughly equal . The higher end of the range is provided by the late 6th - century military historian Agathias , who gives a global total of 645 , 000 effectives for the army " in the old days " , presumed to mean when the empire was united . This figure probably includes fleets , giving a total of c . 600 , 000 for the army alone . Agathias is supported by A . H . M . Jones ' " Later Roman Empire " ( 1964 ) , which contains the fundamental study of the late Roman army . Jones calculated a similar total of 600 , 000 ( exc . fleets ) by applying his own estimates of unit strength to the units listed in the " Notitia Dignitatum " . Following Jones , Treadgold suggests 300 , 000 for the East in 395 . But there are strong reasons to view 200 , 000 as more likely : The discrepancy in army size estimates is mainly due to uncertainty about the size of " limitanei " regiments , as can be seen by the wide range of estimates in the table below . Jones suggests " limitanei " regiments had a similar size to Principate auxilia regiments , averaging 500 men each . More recent work , which includes new archaeological evidence , tends to the view that units were much smaller , perhaps averaging 250 . There is less dispute about " comitatus " regiments , because of more evidence . Treadgold estimates the 5 " comitatus " armies of the East as containing c . 20 , 000 men each , for a total of c . 100 , 000 , which constitutes either one - third or one - half of the total army . About one third of the army units in the " Notitia " are cavalry , but cavalry numbers were less than that proportion of the total because cavalry unit sizes were smaller . The available evidence suggests that the proportion of cavalry was about one - fifth of the total effectives : in 478 , a " comitatus " of 38 , 000 men contained 8 , 000 cavalry ( 21 % ) . Higher Command . The later 4th - century army contained three types of army group : ( 1 ) Imperial escort armies ( " comitatus praesentales " ) . These were ordinarily based near Constantinople , but often accompanied the emperors on campaign . ( 2 ) Regional armies ( " comitatus " ) . These were based in strategic regions , on or near the frontiers . ( 3 ) Border armies ( " exercitus limitanei " ) . These were based on the frontiers themselves . The command structure of the Eastern army , as recorded in the " Notitia Dignitatum " , is represented diagramatically in the organisation chart ( above ) . By the end of the 4th century , there were 2 " comitatus praesentales " in the East . They wintered near Constantinople at Nicaea and Nicomedia . Each was commanded by a " magister militum " ( " master of soldiers " , the highest military rank ) Each " magister " was assisted by a deputy called a " vicarius " . There were 3 major regional " comitatus " , also with apparently settled winter bases : Oriens ( based at Antioch ) , Thraciae ( Marcianopolis ) , Illyricum ( Sirmium ) plus two smaller forces in Aegyptus ( Alexandria ) and Isauria . The large " comitatus " were commanded by " magistri " , the smaller ones by " comites " . All five reported direct to the eastern " Augustus " . This structure remained essentially intact until the 6th century . Army Organization . Units were classified according to whether they were attached to the guard ( " excubitores " and " scholae " ) , the field armies ( " palatini " and " comitatenses " ) or the border armies ( " limitanei " ) . The strength of these units is very uncertain and may have varied over the 5th and 6th centuries . Size may also have varied depending on the status of the regiment . The table below gives some recent estimates of unit strength , by unit type and grade : The overall picture is that " comitatenses " units were either c . 1 , 000 or c . 500 strong . " Limitanei " units would appear to average about 250 effectives . But much uncertainty remains , especially regarding the size of " limitanei " regiments , as can be seen by the wide ranges of the size estimates . Excubitores . The Emperor Leo I created the " Excubitores " as an elite bodyguard of about 300 soldiers . Scholae . The emperor Constantine I created the " Scholae Palatinae " as an elite guards unit of about 6 , 000 soldiers , and to replace the Praetorian Guard of about 10 , 000 soldiers . 40 select troops from the " scholae " , called " candidati " from their white uniforms , acted as the emperor ' s personal bodyguards . Apart from the " Agentes in Rebus " , the " Scholae " were originally organized as cavalry units to accompany the emperors on campaign , although later , individual members of the " Scholae " could have non - military missions . Eventually , Justinian auctioned off positions in what was still a prestigious ceremonial unit , but no longer a fighting force . They were outside the normal military chain of command as they did not belong to the " comitatus praesentales " and reported to the " magister officiorum " , a civilian official . However , this was probably only for administrative purposes : on campaign , the tribunes commanding each " schola " probably reported direct to the emperor himself . The " Notitia Dignitatum " lists 7 scolae of cavalry and 1 of agents in the East Roman empire , as well as 5 of cavalry and 1 of agents in the West Roman empire . Palatini and Comitatenses . " Comitatenses " cavalry units were known as " vexillationes " , infantry units as either " legiones " or " auxilia " . About half the units in the " comitatus " , both cavalry and infantry , were classified as " palatini " . The palatini were the majority of the " comitatus praesentales " ( 80 % of regiments ) and constituted a minority of the regional " comitatus " ( 14 % ) . The " palatini " were an elite group with higher status and probably pay . The majority of cavalry units in the " comitatus " were traditional melee formations ( 61 % ) . These units were denoted " scutarii " , " stablesiani " or " promoti " , probably honorific titles rather than descriptions of function . 24 % of regiments were light cavalry : " equites Dalmatae " , " Mauri " and " sagittarii " ( mounted archers ) . 15 % were heavily armoured shock charge cavalry : " cataphracti " and " clibanarii " Limitanei . The limitanei garrisoned fortifications along the borders of the Roman Empire . They were lower - status and lower - paid than the comitatenses and palatini . The nature of the limitanei changed considerably between their introduction in the 3rd or 4th century and their disappearance in the 6th or 7th century . In the 4th century , the limitanei were professional soldiers , and included both infantry and cavalry as well as river flotillas , but after the 5th century they were part - time soldiers , and after the 6th century they were unpaid militia . The role of the limitanei appears to have included garrisoning frontier fortifications , operating as border guards and customs police , and preventing small - scale raids . Recruitment . Although the East Roman army sometimes turned to conscription it usually relied on volunteer soldiers . Shortages of money , rather than of manpower , usually limited recruitment . In 395 , the army used Latin as its operating language . This continued to be the case into the late 6th century , despite the fact that Greek was the common language of the Eastern empire . This was not simply due to tradition , but also to the fact that about half the Eastern army continued to be recruited in the Latin - speaking Danubian regions of the Eastern empire . An analysis of known origins of " comitatenses " in the period 350 - 476 shows that in the Eastern army , the Danubian regions provided 54 % of the total sample , despite constituting just 2 of the 7 eastern dioceses ( administrative divisions ) : Dacia and Thracia . These regions continued to be the prime recruiting grounds for the East Roman army e . g . the emperor Justin I ( r . 518 - 27 ) , uncle of Justinian I , was a Latin - speaking peasant who never learnt to speak more than rudimentary Greek . The Romanized Thracian ( Thraco - Roman ) and Illyrian inhabitants of those regions , who came to be known as Vlachs by foreigners in the Middle Ages , retained the Roman name ( Romanians ) and the Latin tongue . Tactics . Heavy infantry . The East Roman heavy infantry relied on their spears and shields in close combat . These weapons were most effective when the soldiers fought in formation . Maurikios ' Strategikon . The Strategikon is the earliest surviving Roman / Byzantine cavalry manual , and directly influenced later Byzantine military manuals . The Strategikon describes the organization , equipment , and tactics of the east Roman army at the end of this period . Equipment . The east Roman army included both light and heavy infantry , as well as light and heavy cavalry . The equipment of the East Roman army changed considerably between the 4th and 7th Centuries . By the end of the period , the cavalry had armor and horse armor , with both bows and lances as weapons . The heavy infantry still had armor , with large shields , spears , and swords . The light infantry had bows . M . C . Bishop and J . C . M . Coulston , in a major work on Roman military equipment , do not distinguish the equipment of the various branches of the Roman military . It is doubtful whether there were any universal differences between the equipment of the palatini , comitatenses , and limitanei . The late Roman empire had centralized fabricae , introduced by Diocletian , to provide arms and armor for the army . The introduction of the centralized fabricae , where earlier armies had relied on legionary workshops , may reflect the needs of the field armies . The basic equipment of a 4th - century foot soldier was essentially the same as in the 2nd century : metal armour cuirass , metal helmet , shield and sword . Some evolution took place during the 3rd century . Trends included the adoption of warmer clothing ; the disappearance of distinctive legionary armour and weapons ; the adoption by the infantry of equipment used by the cavalry in the earlier period ; and the greater use of heavily armoured cavalry called cataphracts . Clothing . According to the " Strategikon " , the cavalry soldiers should have long " Avar " tunics reaching past the knees , and large cloaks with sleeves . According to the " Strategikon " , the infantry soldiers should have long " Gothic " tunics reaching the knees , or short ones with split sides , as well as " Gothic " shoes with thick hobnailed soles , and " Bulgarian " cloaks . In the 1st and 2nd centuries , a Roman soldier ' s clothes consisted of a single - piece , short - sleeved tunic whose hem reached the knees and special hobnailed sandals ( " caligae " ) . This attire , which left the arms and legs bare , had evolved in a Mediterranean climate and was not suitable for northern Europe in cold weather . In northern Europe , long - sleeved tunics , trousers ( " bracae " ) , socks ( worn inside the " caligae " ) and laced boots were commonly worn in winter from the 1st century . During the 3rd century , these items of clothing became much more widespread , apparently common in Mediterranean provinces also . However , it is likely that in warmer weather , trousers were dispensed with and " caligae " worn instead of socks and boots . Late Roman clothing was often highly decorated , with woven or embroidered strips , " clavi , " and circular roundels , " orbiculi , " added to tunics and cloaks . These decorative elements usually consisted of geometrical patterns and stylised plant motifs , but could include human or animal figures . A distinctive part of a soldier ' s costume , though it seems to have also been worn by non - military bureaucrats , was a type of round , brimless hat known as the pannonian cap ( " pileus pannonicus " ) . Armour . In the 3rd century , troops are depicted wearing mail or scale armour . The artistic record shows that most late soldiers wore metal armour , despite Vegetius ' statement to the contrary . For example , illustrations in the " Notitia " show that the army ' s " fabricae " ( arms factories ) were producing mail armour at the end of the 4th century . Actual examples of both scale armour and quite large sections of mail have been recovered , at Trier and Weiler - La - Tour respectively , within 4th - century contexts . Officers generally seem to have worn bronze or iron cuirasses , as in the days of the Principate , together with traditional " pteruges " . The cataphract and " clibanarii " cavalry , from limited pictorial evidence and especially from the description of these troops by Ammianus , seem to have worn specialist forms of armour . In particular their limbs were protected by laminated defences , made up of curved and overlapping metal segments : " " Laminarum circuli tenues apti corporis flexibus ambiebant per omnia membra diducti " " ( Thin circles of iron plates , fitted to the curves of their bodies , completely covered their limbs ) . Helmets . In general , Roman cavalry helmets had enhanced protection , in the form of wider cheek - guards and deeper neck - guards , for the sides and back of the head than infantry helmets . Infantry were less vulnerable in those parts due to their tighter formation when fighting . During the 3rd century , infantry helmets tended to adopt the more protective features of cavalry helmets of the Principate . Cheek - guards could often be fastened together over the chin to protect the face , and covered the ears save for a slit to permit hearing e . g . the " Auxiliary E " type or its Niederbieber variant . Cavalry helmets became even more enclosed e . g . the " Heddernheim " type , which is close to the medieval great helm , but at the cost much reduced vision and hearing . In contrast , some infantry helmets in the 4th century reverted to the more open features of the main Principate type , the " Imperial Gallic " . The " Intercisa " design left the face unobstructed and had ear - holes in the join between cheek - guards and bowl to allow good hearing . In a radical change from the earlier single - bowl design , the Intercisa bowl was made of two separate pieces joined by a riveted ridge in the middle ( hence the term " ridge helmet " ) . It was simpler and cheaper to manufacture , and therefore probably by far the most common type , but structurally weaker and therefore offered less effective protection . The " Berkasovo " type was a more sturdy and protective ridge helmet . This type of helmet usually has 4 to 6 skull elements ( and the characteristic median ridge ) , a nasal ( nose - guard ) , a deep brow piece riveted inside the skull elements and large cheekpieces . This was probably the cavalry version , as the cheekpieces lack ear - holes . Unusually the helmet discovered at Burgh Castle , in England , is of the Berkasovo method of construction , but has cheekpieces with earholes . Face - guards of mail or in the form of metal ' anthropomorphic masks , ' with eye - holes , were often added to the helmets of the heaviest forms of cavalry , especially " cataphracti " . Despite the apparent cheapness of manufacture of their basic components , many surviving examples of Late Roman helmets , including the Intercisa type , show evidence of expensive decoration in the form of silver or silver - gilt sheathing . A possible explanation is that most of the surviving exemplars may have belonged to officers and that silver - or gold - plating denoted rank ; and , in the case of mounted gemstones , high rank e . g . the ornate Deurne helmet , believed by some historians to have belonged to a senior officer . Other academics , in contrast , consider that silver - sheathed helmets may have been widely worn by " comitatus " soldiers , given as a form of pay or reward . Some East Roman soldiers wore mail or scale hoods for head protection ; these could be part of mail coats or could be separate coif s . Similar armoured hoods appear in an illustration in the Vergilius Vaticanus . Shields . Shields were both protective equipment for the soldiers and insignia for their units . Both Vegetius , in De re Militari , and Mauricius , in the Strategikon , emphasize that each unit should have distinctive shields . Lance - armed cavalry carried shields , although bow - armed cavalry generally did not . All troops adopted the auxiliary oval ( or sometimes round ) shield ( " clipeus " ) . Shields , from examples found at Dura and Nydam , were of vertical plank construction , the planks glued , and faced inside and out with painted leather . The edges of the shield were bound with stitched rawhide , which shrank as it dried improving structural cohesion . It was also lighter than the edging of copper alloy used in earlier Roman shields . Hand - to - hand weapons . The East Roman heavy infantry relied on the spear in close combat . No late Roman or East Roman spear shafts survive , but I . P . Stephenson suggests that East Roman spears may have been as long as northern European spears discovered in the bog deposits at Illerup and Nydam , between 2 . 23 meters and 3 . 54 meters long . The infantry adopted the " spatha " , a longer ( median length : 760 mm / 30 in ) sword that during the earlier centuries was used by the cavalry only . In addition , Vegetius mentions the use of a shorter - bladed sword termed a " semispatha . " At the same time , infantry acquired a heavy thrusting - spear ( " hasta " ) which became the main close order combat weapon to replace the " gladius " , as the " spatha " was too long to be swung comfortably in tight formation ( although it could be used to stab ) . These trends imply a greater emphasis on fighting the enemy " at arm ' s length " . Short , single - edged knives were also used , although probably as tools rather than weapons . These appear in 4th - century graves with military belt fittings , and similar tools appear in 4th through 7th - century contexts . Missile weapons . In addition to his thrusting - spear , a late foot soldier might also carry a throwing - spear ( " verutum " ) or a " spiculum " , a kind of heavy , long " pilum " , similar to an angon . Alternatively , a couple of short javelins ( " lanceae " ) . Late infantrymen often carried half a dozen lead - weighted throwing - darts called " plumbata e " ( from " plumbum " = " lead " ) , with an effective range of c . , well beyond that of a javelin . The darts were carried clipped to the back of the shield . The late foot soldier thus had greater missile capability than his Principate predecessor , who was usually limited to just two " pila " . Late Roman archers continued to use the recurved composite bow as their principal weapon . This was a sophisticated , compact and powerful weapon , suitable for mounted and foot archers alike ( the cavalry version being more compact than the infantry ' s ) . A small number of archers may have been armed with crossbows ( " manuballistae " ) . Campaigns . In the 6th century , the emperor Justinian I , who reigned from 527 to 565 , sent much of the East Roman army to try to reconquer the former West Roman empire . In these wars , the East Roman empire reconquered parts of North Africa from the Vandal kingdom and Italy from the Ostrogothic kingdom , as well as parts of southern Spain . In the 7th century , the emperor Heraclius led the east Roman army against the Sassanid empire , temporarily regaining Egypt and Syria , and then against the Rashidun Caliphate . His defeat at the Battle of Yarmuk would lead to the Islamic conquest of Syria and Egypt , and would force the reorganization of the East Roman army , leading to the thematic system of later Byzantine armies .