The tzaousios (Greek: τζαούσιος) was a late Byzantine military office, whose exact functions and role are somewhat unclear.[1]
The term is derived from the Turkish çavuş, meaning "courier" or "messenger",[1] and was in use by the Byzantines perhaps as early as the late 11th century.[2] In the 13th–15th centuries, it became applied to officers serving in provincial posts. A tzaousios could serve as commander of the garrison of a kastron (a fortified administrative center run by a kephale), possibly combining the military and administrative roles, to the megala allagia of the imperial field army.[1][2] Most of the tzaousioi mentioned in the sources came from the Byzantine Morea,[3] where they played an important role in provincial administration. In Macedonia and Thrace by contrast, they seem to have been limited to a purely military role within the megala allagia.[2]
The title of megas tzaousios (Greek: μέγας τζαούσιος, "grand tzaousios") is first attested under John III Vatatzes (r. 1221–1254). His functions are unclear.[4] The French Byzantinist Rodolphe Guilland suggested that he was in command of subordinated tzaousioi, who acted as the successors of the earlier imperial courier corps, the mandatores.[5] In pseudo-Kodinos's mid-14th century Book of Offices, he is described as being responsible for maintaining the order of the imperial retinue.[3] Certainly, the first megas tzaousios, Constantine Margarites, was the commander of Vatazes's personal retinue,[6] but in later times, it does not appear to have had a fixed function.[7]