Roman Cavalry Rank Structure

[Lothia]

Ave Civitas,

Once again I have exhausted my sources so I turn to the experts. I hate bothering you people, but I am stuck.

I am seeking information about Roman Cavalry during the time of Constantine the Great.

In particular, I seek this information:

1. Command structure
The Quingenaria was commanded by a Princeps, I believe.
The Turmae was commanded by the Decurio.

Was there an intermediate command between the 500 and the 32?

2. Command structure
Did the Quingenaria commander have an assistant (second-in-command)?
If he did, what was his rank?

3. Command structure
The Turmae was commanded by a Decurio.
The title Decurio refers to ten.
Was the Decurio commanding the Turmae similar to the Centurion commanding the Cohort? That is, a centurion promoted to a higher command level but retaining the same title.

As an example, a Turmae (with 32 men) could have (and I find no examples of this) three ten man cavalry units, each commanded by a Decurio.

The most senior of the Decurios then commanding the Turmae.

4. Billeting
The Infantry Century was housed in 8-man rooms called the contubernium.

Where the cavlary barracks also divided into similar rooms?
If they were, what would they be called?

I thank you again for your assistance. As always, you guys are great.

Tom.

[D B Campbell]

I am seeking information about Roman Cavalry during the time of Constantine the Great.

Good luck with that!

The Quingenaria was commanded by a Princeps, I believe.
The Turmae was commanded by the Decurio.

An imperial ala quingenaria was commanded by a prefect (praefectus alae).

Princeps seems to be a function, rather than a rank, indicating a man seconded to a particular command. A typical princeps might be a centurion, who could safely be seconded to command the rump of a regiment which had been split for some reason. So, no -- the ala wasn't commanded by a princeps.

As you say, each troop (turma; turmae is the plural) was commanded by a decurion (decurio).

Did the Quingenaria commander have an assistant (second-in-command)? If he did, what was his rank?

The prefect doesn't appear to have had a second-in-command.
He would have an administrative staff, though.

The Turmae was commanded by a Decurio.
The title Decurio refers to ten. Was the Decurio commanding the Turmae similar to the Centurion commanding the Cohort? That is, a centurion promoted to a higher command level but retaining the same title.

Actually a Decuria is a group of ten men, or sometimes a group numbering a tenth of the whole. But in auxiliary regiments, the turma seems to be a group of 32 men. (The Hadrianic writer Arrian is our only source for this. Scholars usually hedge their bets by claiming 30-odd men, which could range up to 42!)
So, no -- the decurion wasn't specially promoted above his level. He normally commanded "30-odd" men.

As an example, a Turmae (with 32 men) could have (and I find no examples of this) three ten man cavalry units, each commanded by a Decurio. The most senior of the Decurios then commanding the Turmae.

There's no evidence of this. (imho it doesn't seem very likely.)

Where the cavlary barracks also divided into similar rooms? If they were, what would they be called?

Yes, cavalry barracks were similarly subdivided, although we're not sure how many men (and horses!) shared a room.

Incidentally, there's no evidence that the rooms (rather than the groups of men) were called contubernia, although they may well have been. After all, the barrack blocks appear to have been called centuriae.

Hope some of that helps.

[Lothia]

Ave, Master Campbell,

Thanks for helping with the rank structure questions. Perhaps today's view of command structure was different than theirs. It seems odd that if, in a battle, the commander was incompacitated there was no other to look to for command and control.

As always, you guys are great. When I have exhausted my own library and internet searches, I know I can always count on you gentlemen (and ladies)

Me. (Lothia)