Tagma ( military ) The tagma ( , pl . tagmata ) is a term for a military unit of battalion or regiment size . The best - known and most technical use of the term however refers to the elite regiments formed by Byzantine emperor Constantine V and comprising the central army of the Byzantine Empire in the 8th – 11th centuries . History and role . In its original sense , the term " tagma " ( from the Greek τάσσειν , " to set in order " ) is attested from the 4th century and was used to refer to an infantry battalion of 200 – 400 men ( also termed " bandum " or " numerus " in Latin , " arithmos " in Greek ) in the contemporary East Roman army . In this sense , the term continues in use in the modern Greek military ( " cf . " Greek military ranks ) . Imperial guards , 8th – 10th centuries . In later Byzantine usage , the term came to refer exclusively to the professional , standing troops , garrisoned in and around the capital of Constantinople . Most of them traced their origins to the Imperial guard units of the later Roman Empire . By the 7th century , these had declined to little more than parade troops , meaning that the emperors were hard put to face the frequent revolts of the new and powerful thema tic formations , especially the Opsician Theme , the Asian theme closest to the capital . Within the first sixty years since its creation , it was involved in five revolts , culminating in the rebellion and usurpation of the throne by its commander , the Count Artabasdos , in 741 – 743 . After putting down the revolt , Emperor Constantine V ( r . 741 – 775 ) reformed the old guard units of Constantinople into the new " tagmata " regiments , which were meant to provide the emperor with a core of professional and loyal troops , both as a defense against provincial revolts , and also , at the time , as a formation devoted to Constantine ' s iconoclastic policies . The " tagmata " were exclusively heavy cavalry units , more mobile than the theme troops , and maintained on a permanent basis . During the defensive phase of the Empire in the 8th and 9th centuries , their role was that of a central reserve , garrisoned in and around the capital , in regions such as Thrace and Bithynia . They formed the core of the imperial army on campaign , augmented by the provincial levies of thematic troops , who were more concerned with local defense . In addition , like their Late Roman counterparts , they served as a recruiting and promotion ground for young officers . A career in a " tagma " could lead to a major commands in the provincial thematic armies or a high court appointment , as promising young men had the opportunity to catch the Emperor ' s attention . Officers in the " tagmata " came primarily either from the relatively well - off urban aristocracy and officialdom , or the landed aristocracy of the Anatolian themes , which increasingly came to control the higher military offices of the state . Nevertheless , the " tagmata " , as indeed military and state service in general , offered a degree of upwards social mobility for the lower strata of society . In their heyday in the 9th and early 10th centuries , there were four " tagmata " proper ( " τὰ δʹ τάγματα " ) : Other units closely related to the " tagmata " , and often included among them , were : In addition , there was also the " Hetaireia " ( Gr . , " Companions " ) , which comprised the mercenary corps in Imperial service , subdivided in Greater , Middle and Lesser , each commanded by a respective " Hetaireiarchēs " . Organization . There is much debate as to the exact size and composition of the imperial " tagmata " , owing to the inaccuracy and ambiguity of the few contemporary sources ( military manuals , lists of offices and Arab accounts , primarily from the 9th century ) that deal with them . Our primary sources , the accounts of Arab geographers Ibn Khurdādhbah and Qudāmah are somewhat ambiguous , but they give the overall " tagmata " strength at 24 , 000 . This figure has been seen by many scholars , such as John Bagnell Bury and John Haldon , as too high , and revised estimates put the strength of each " tagma " at 1 , 000 – 1 , 500 men . Others , like Warren Treadgold and ( in part ) Friedhelm Winkelmann , accept these numbers , and correlate them with the lists of officers in the " Klētorologion " to reach an average size of 4 , 000 for each " tagma " ( including the " Optimatoi " and the " Noumeroi " , for which it is explicitly stated that they numbered 4 , 000 each ) . The tagmatic units were all organized along similar lines . They were commanded by a " domestikos " , except for the " Vigla " , which was commanded by a " droungarios " . He was assisted by one or two officers called " topotērētēs " ( Gr . τοποτηρητής , lit . " placeholder " , " lieutenant " ) , each of whom commanded one half of the unit . Unlike the thematic units , there were no permanent intermediate command levels ( " tourmarchai " , " chiliarch oi " or " pentakosiarchai " ) until Leo VI introduced the " droungarios " ca . after 902 . The largest subdivision of the " tagmata " was the " bandon " , commanded by a " komēs " ( " count " ) , called " skribōn " in the " Exkoubitores " and " tribounos " ( " tribune " ) in the " Noumeroi " and Walls units . The " banda " in turn were divided in companies , headed by a " kentarchos " ( " centurion " ) , or " drakonarios " ( " draconarius " ) for the " Exkoubitores " , and " vikarios " ( " vicar " ) for the " Noumeroi " and Walls units . The " domestikos tōn Scholōn " , the head of the " Scholai " regiment , became gradually more and more important , eventually coming to be the most senior officer of the entire army by the end of the 10th century . The following table illustrates the structure of the " Scholai " in the 9th century , according to Treadgold : In addition , there were a " chartoularios " ( χαρτουλάριος , " secretary " ) and a " prōtomandatōr " ( πρωτομανδάτωρ , " head messenger " ) , as well as 40 standard bearers ( βανδοφόροι , " bandophoroi " ) , of varying ranks and titles in each " tagma " , and 40 " mandator es " ( " messengers " ) , for a total unit size of 4 , 125 . On campaign , every tagmatic cavalryman was accompanied by a servant . The next table gives the evolution of the theoretical establishment size of the entire imperial tagmatic force , again as calculated by Warren Treadgold : Professional regiments , 10th – 11th centuries . As the Byzantine Empire embarked on its campaigns of reconquest in the 10th century , the " tagmata " became more active , and were posted often in garrison duties in the provinces or in newly conquered territories . In addition to the older units , a number of new and specialized units were formed to meet the demands of this more aggressive style of warfare . Michael II ( r . 820 – 829 ) raised the short - lived " Tessarakontarioi " , a special marine unit ( named after their high pay of 40 " nomisma ta " ) , and John I Tzimiskes ( r . 969 – 976 ) created a heavy cataphract corps called the " Athanatoi " ( , the " Immortals " ) after the old Persian unit , which were revived in the late 11th century by Michael VII Doukas ( r . 1071 – 1078 ) . Other similar units were the " Stratēlatai " , likewise formed by John Tzimiskes , the short - lived " Satrapai " of the 970s , the " Megathymoi " of the 1040s or the " Archontopoulai " and " Vestiaritai " of Alexios I . Many of the new " tagmata " were composed of foreigners , such as the " Maniakalatai " , formed by George Maniakes from Franks in Italy , or the most famous of all tagmatic units , the 6 , 000 - strong mercenary Varangian Guard ( ) , established ca . 988 by Emperor Basil II ( r . 976 – 1025 ) . The reign of Basil II also saw the beginnings of a profound transformation of the Byzantine military system . In the mid - 10th century , the decline in the numbers of the thematic forces and the exigencies of the new offensive strategy on the eastern border gave rise to an increasing number of provincial " tagmata " , permanent professional forces modelled after the imperial " tagmata " . The great conquests in the East in the 960s were secured by the creation of an array of smaller " themata " , in which detachments of these professional forces were based , eventually to be grouped under regional commanders with the title of " doux " or " katepanō " . This strategy was effective against small - scale local threats , but the concurrent neglect of the thematic forces reduced the state ' s ability to respond effectively to a major invasion that succeeded in penetrating the frontier buffer zone . The decline of the part - time thematic armies and the increasing reliance on a large array of permanent units , both indigenous and mercenary , was based not only on the greater military effectiveness of the latter in the more offensive Byzantine strategy of the era , but also on their greater reliability as opposed to the thematic troops with their local ties . The " tagmata " recruited from the larger " themata " were probably 1 , 000 men strong , while those from the smaller " themata " may have numbered ca . 500 men . Foreign , chiefly Frankish mercenary units , also seem to have numbered 400 – 500 men . Consequently , in the 11th century , the distinction between " imperial " and provincial forces largely vanished , and the term " tagma " was applied to any permanent formed regiment , and regional origins and identities are prominently displayed in the units ' titles . After ca . 1050 , like the thematic armies , the original " tagmata " slowly declined , and were decimated in the military disasters of the latter third of the 11th century . Except for the Varangians , the " Vestiaritai " , the " Hetaireia " and the " Vardariōtai " , the older guard units disappear altogether by ca . 1100 and are absent from the 12th - century Komnenian army . In the Komnenian army , the term " tagma " reverted to a non - specific meaning of " military unit " .