The Excubitors were founded in c. 460 as an imperial guard-unit by the Byzantine emperor Leo I the Thracian. The 300-strong force, originally recruited from among the warlike mountain tribe of the Isaurians, replaced the older Scholae Palatinae as the main imperial bodyguards. The Excubitors remained an active military unit for the next two centuries, although, as imperial bodyguards, they did not often go on campaign. Their commander, the Count of the Excubitors, soon acquired great influence. Justin I was able to use this position to rise to the throne in 518, and thereafter the Counts of the Excubitors were among the main political power-holders of their day; two more, Tiberius II Constantine and Maurice, rose to become emperors in the late 6th century.

The Scholae Palatinae were an elite military imperial guard unit, usually ascribed to the Roman Emperor Constantine the Great as a replacement for the equites singulares Augusti, the cavalry arm of the Praetorian Guard. The Scholae survived in Roman and later Byzantine service until they disappeared from the historical record in the late 11th century, during the reign of Alexios I Komnenos.