Vigla ( tagma ) The Vigla ( , " guard watch " , from ) , also known as the Arithmos ( , " Number " ) and in English as the Watch , was one of the elite " tagmata " of the Byzantine army . It was established in the latter half of the 8th century , and survived until the late 11th century . Along with the " Noumeroi " regiment , the " Vigla " formed the guard of the imperial palace in Constantinople , and was responsible for the Byzantine emperor ' s safety on expeditions . History and functions . The " Vigla " or " Arithmos " was the third of the imperial " tagmata " to be established , with its commander attested for the first time in 791 . Both names derive from the Latin terminology of the Late Roman army : the term " vigilia " was applied from the 4th century onto any kind of guard detachment , while " arithmos " is the Greek translation of the Latin " numerus " , both titles being used in a generic sense for " regiment " . In literary sources , " Vigla " is more commonly used than " Arithmos " , and is also the title used in the seals of its commanders . Its exact date of creation is contested among modern historians of the Byzantine army : Byzantinist John Haldon considers that the " Vigla " was established as a " tagma " by the Empress Irene in the 780s out of a provincial brigade , but Warren Treadgold supports its creation along with the first two " tagmata " , the " Scholai " ( " Schools " ) and " Exkoubitoi " ( " Excubitors " ) , by Emperor Constantine V ( r . 741 – 775 ) in the mid - 8th century . If the former hypothesis is true , then the establishment of the " Vigla " by Irene may have been intended to counterbalance the two older " tagmata " , which remained loyal to iconoclasm and resented Irene ' s iconophile policies . The provincial parent unit , in turn , appears to have been of considerable ancestry : the presence of archaic Late Roman titles for its officers points to an origin , possibly as a cavalry vexillation , in the old East Roman army before the Muslim conquests of the 7th century . John B . Bury has traced a hypothetical lineage to the early 5th - century " vexillationes palatinae " of the " Comites Arcadiaci " , the " Comites Honoriaci " and the " Equites Theodosiaci " . Along with many of the other " tagmata " , the " Vigla " disappeared in the decades of crisis in the late 11th century : it is last mentioned in 1094 . As the name indicates , the " Vigla " was tasked with guard duties , both in the imperial palace and on campaign . Unlike the other cavalry " tagmata " , which were mostly garrisoned outside Constantinople in Thrace and Bithynia , the " Vigla " had a significant presence in the capital . There , its task was guarding the imperial palace , along with the less prestigious infantry " tagmata " of the " Noumeroi " ( responsible also for the palace prisons ) and the " Teicheiōtai " ( guarding the city walls ) . More specifically , within Constantinople , the " Vigla " guarded the most exposed western , city - ward perimeter of the palace precinct , and kept a permanent garrison at the Covered Hippodrome , which was left in place even when the rest of the unit was on campaign , and secured the safety of the emperor while he was outside the Palace . As the regimental commander , the " droungarios tēs viglas " ( Greek : ) was always in attendance to the emperor , the " Vigla " could go on campaign without him , in which case it came under the orders of the Domestic of the Schools . On expeditions led by the emperor himself , the " droungarios " was responsible for the safety of the camp and especially the night watch , relaying the emperor ' s orders , the advance , rear and flank guards during marches , and guarding prisoners of war . Organisation . As with the other " tagmata " , the issue of the unit ' s size is a matter of controversy . Warren Treadgold considers the " tagmata " to have numbered a standard 4 , 000 men each , while other scholars , notably John Haldon , argue in favour of a much lower size of circa 1 , 000 men . The structure of the imperial " tagmata " , however , was uniform and is well - attested , with minor variations , mostly in titelature , reflecting the different origins of the units . Uniquely among the " tagmata " , and perhaps a reflection of its ancestry , since it was more common in the 6th century , the commander of the " Vigla " bore the title of " droungarios " , in English sometimes rendered as " Drungary of the Watch " . The first known holder of the office was Alexios Mosele in 791 . Due to his proximity to the emperor , the " droungarios " was usually a close and trusted aide , as well as one of the senior military officers of the state . In the 10th century , the office was given to some of the most distinguished scions of the Byzantine military aristocracy , but from circa 1030 on , it was transformed into a civil office with judicial responsibilities . In this capacity , it survived well beyond the regiment ' s demise and unto the end of the Palaiologan period . Under the " droungarios " were one or two " topotērētai " ( sing . " topotērētēs " , Greek : τοποτηρητής , lit . " placeholder , lieutenant " ) , a " chartoularios " ( Greek : ) as head of the commander ' s secretariat , and the " akolouthos " , a title unique to the " Vigla " but corresponding to similar subaltern officers , the " proximos " of the " Scholai " and the " prōtomandatōr " of the " Exkoubitoi " . The unit was divided into twenty " banda " ( sing . " bandon " , Greek : βάνδον , from , " banner " ) , each of theoretically 50 men , commanded by a " komēs " ( Greek : , " count [ of the " arithmos " ] " ) . In turn , each of these commanded five " kentarchoi " ( sing . " kentarchos " , Greek : κένταρχος , " centurion " ) . Among the lower ranks within each " tagma " were two further classes of subaltern officers , the " bandophoroi " ( Greek : βανδοφόροι , " banner - bearers " ) and the " mandator es " ( Greek : μανδάτορες , " messengers " ) . Each " tagma " numbered forty of the " bandophoroi " , divided into four different classes of ten , with differing titles in each unit . For the " Vigla " in particular , these titles can be traced to the standard Roman cavalry ranks of the 5th – 6th centuries . These were : the " bandophoroi " , the " labourisioi " ( Greek : λαβουρίσιοι , a corruption of 6th - century " labarēsioi " , " carriers of the " labarum " " ) , the " sēmeiophoroi " ( Greek : σημειοφόροι , " bearers of an insigne " , cf . the Late Roman " semafori " ) , and the " doukiniatores " ( Greek : δουκινιάτορες , again a corruption of the Latin " ducenarii " of the Late Roman military ) . The " Vigla " also was unique in having several ranks of messengers : along with the ordinary " mandatores " present in the other units , it included " legatarioi " ( Greek : λεγατάριοι , " legate es " ) , " thyrōroi " ( Greek : θυρωροί , " doorkeepers " ) , " skoutarioi " ( Greek : σκουτάριοι , " shield - bearers " ) and " diatrechontes " ( Greek : διατρέχοντες , " runners " ) .