Allagion The allagion ( ) was a Byzantine military term designating a military unit . It first appeared in the mid - to - late 10th century , and by the 13th century had become the most frequent term used for the Byzantine army ' s standing regiments , persisting until the late 14th century . Origin of the term . The term means " rotation of duties " , and first appears in the latter half of the 10th century as an alternate term for a cavalry " bandon " , numbering between 50 and 400 men . In the 10th and 11th centuries , provincial " allagia " had some 50 – 150 men , while those of the central imperial army were closer to the upper limit , with circa 320 – 400 men . Palaiologan " allagia " . By the late 13th century , the term had largely replaced the earlier " tagma " in colloquial and technical ( although not entirely in literary ) usage to designate any standing regiment . The Byzantine emperor ' s own " allagion " ( i . e . his military retinue ) seems to have been replaced by the two divisions of the rather obscure " Paramonai " corps , one on foot and one on horse . These , however , were still commanded , according to Pseudo - Kodinos , by an allagatōr ( ) each , while the protallagatōr ( πρωταλλαγάτωρ , " first " allagatōr " " ) probably commanded the corps as a whole . The " allagia " of the provincial army were divided into two distinct groups : the " imperial " allagia " ( , " basilika allagia " ) and the " great " allagia " ( , " megala allagia " ) . The former were found in Byzantine Asia Minor , while the latter in the Empire ' s European provinces alone . With the gradual fall of Asia Minor to the Turks during the late 13th and early 14th centuries , the " imperial " allagia " " finally disappeared . The " great " allagia " " , of which three are known by name – the Thessalonian ( ) , that of Serres ( ) , and that of Bizye ( ) – are first attested in 1286 and continue to be mentioned until 1355 . Almost certainly , however , they date at least from the reign of Emperor Michael VIII Palaiologos ( r . 1259 – 1282 ) , and perhaps even before him to the Laskarid emperors of Nicaea who conquered these lands . They too disappeared as their provinces fell to the Serbs and the Ottoman Turks . The exact role , nature and structure of the European " megala allagia " are not fully clear ; they encompassed the regions around these cities , conforming roughly to the old " themata " of Thessalonica , Strymon , and Thrace . They may therefore represent an attempt to centralize control over the provincial military forces , at a time when " political " control was increasingly devolving from the capital to the periphery . How extensive their reach was is , however , open to question . It is known that their forces comprised both frontier troops providing garrisons for fortresses , as well as cavalry " pronoia s " . In addition , they may have included small land - holders and mercenaries . As Mark Bartusis comments on the various attempts to explain their role , " at the one extreme the " megala allagia " were the central element in the late Byzantine army ; every soldier who lived in the provinces and who had a military obligation [ . . . ] was a " megaloallagitēs " . . . " , meaning that they represented a universal military organization involved in the recruitment and maintenance of all provincial forces , from which only the imperial guards and the personal retinues of local governors must be excluded . On the other extreme , the " megala allagia " may have been only a partial aspect of the late Byzantine military system , confined only to some provinces and from which foreign mercenaries were probably excluded . The size of the " allagia " was apparently equivalent to the old " banda " at circa 300 – 500 troops ; thus the " Chronicle of the Morea " records that Constantine Palaiologos had a force of 18 " allagia " or 6 , 000 cavalry troops at his command in the Morea the early 1260s . The commander of the " allagion " seems to have been the archōn tou allagiou ( ) , whose exact relation with the " allagatōr " is unknown . The office of " tzaousios " also occurs in the early 14th century in the context of the " megala allagia " of the region of Thessalonica . Its exact functions , however , within these units are unknown .