The equites singulares Augusti (lit: "personal cavalry of the emperor" i.e. imperial horseguards) during the Principate period of imperial Rome. Based in Rome, they escorted the Roman emperor whenever he left the City on campaign or on tours of the provinces.[1]
The regiment was reconstituted in the late 1st century AD as a milliary ala, under the command of a tribunus militum. Initially, it contained 720 horse, divided into 24 turmae, or squadrons, of 30 men each. Numbers rose to around 1,000 under Hadrian (r. 117-38) and the regiment was expanded to 2,000 horse in the early 3rd century by the emperor Septimius Severus (ruled AD 197-211).[2] The base constructed at this time for the expanded unit has been excavated underneath the Basilica of San Giovanni in Laterano, Rome (see Castra Nova equitum singularium).
Recruited from the finest troopers of the alae (cavalry regiments of the imperial army's auxilia corps), the equites singulares was the only regiment of the Guard that admitted peregrini, imperial subjects who were not Roman citizens. The regiment's original core component were crack Batavi horsemen.[3] On Trajan's Column (AD 113), the standards of the unit are depicted bearing the same lightning-and-thunderbolt motif (with or without wings) as the legions.[4]
It appears that after some campaigns, detachments of singulares were left behind in the provinces, to form the core of new regular alae, which retained the prestigious singulares title and crack reputation e.g. the Ala I Flavia singularium stationed in Raetia in mid 2nd century.[5]
In AD 312, after the defeat of the emperor Maxentius at the battle of the Milvian bridge, the regiment was disbanded, together with the Praetorian Guard, by the emperor Constantine I (ruled 312-37).[6] The unit may already have become redundant, if the scholae, elite cavalry regiments escorting the emperor, had already been established by the emperor Diocletian (ruled 284-305). Alternatively, the scholae may have been founded by Constantine as a direct replacement for the equites singulares.[7]