Equites Singulares Augusti

[Julian de Vries]

According to M.P. Speidel the Emperor Trajan raised the equites Singulares Augusti and that Emperor Septimius Severus doubled the equites Singulares Augusti.

What are the Primary Sources which state these things?

[Robert Vermaat]

Have you read the article?

[Nathan Ross]

What are the Primary Sources which state these things?

There aren't any. Speidel's idea comes, I think, originally from his paper 'Die Denkmäler der Kaiserreiter' (1994?), expanded in Riding for Caesar; I haven't read either, but bits of the latter are available online.

The basis of the theory seems to be that the equites didn't exist under the Julio-Claudian emperors, who had other bodyguards instead (principally the Batavian custodes). Speidel mentions an inscription of AD110 to a tribune of the equites singulares augusti (although I can't find his reference), so they must have appeared some time previously. Some historians - Connolly, I think, for one - suggest Domitian as the founder. Speidel seems to suggest that Trajan may have used his consular singulares as the nucleus for the unit, as he was governor of Germania Inferior when he became emperor and most known early horse-guardsmen seem to come from there (as did the earlier custodes, of course!).

The idea about Severus doubling the horse guard comes, I think, from the construction of the Castra Nova as a second (or replacement?) base under his reign. There's also a debatable reference in Herodian to Severan increasing the number of troops in Rome by four, which some people have suggested meant enlarging the size of the praetorian and perhaps horse guards as well.

[Steven James]

Nathan wrote:
There's also a debatable reference in Herodian to Severan increasing the number of troops in Rome by four, which some people have suggested meant enlarging the size of the praetorian and perhaps horse guards as well.
 
I found this reference to be right and wrong. It works out that the equites singular of the principate are increased by four, but then Herodian is comparing the equites singular of the principate with the total number of praetorian cavalry and urban cavalry. That is how my research rolls.