\'Hyginus\' Cavalry Units

[MD]

My 'dear friend' Polybius is quite specific for the Turmae, giving each one 3 Decurions, each leading the rank of 10 of which he's a part; the senior one of which leads the Turmae - but they were all Decurions......

An imperial turma also includes one duplicarius and one sesquiplicarius in addition to the decurion. Thus it had three officers just like the Polybian Turma with its three decurions. How much more are needed to command a 30 - 32 men unit?

Rather than 16 Decurions = 16 Turma, however, this could therefore be 16 from 6 Turma, with 2 'missing'...

But why should there be free spaces (see Duncan Campbell post above) in the inscription if this are just some random decurions and not the complete list of them in the two Alae?

Is the hay for the Decurion listed separately? Or has his horse's hay been delivered to the Turmae anyway and they'd need 30 x horse-quantity?...

Unfortunately I don't have access to the 1971 book, so I can only repeat what Dixon and Southern said. However since the decurion, duplicarius and sesquiplicarius had extra horses it can't just be the quantity for 30.

That is interesting. I found in D B Campbell's book the information on the 9-blocks, which made perfect sense for permanent Turmae-blocks. But I would love to query the logic on why people would think Turmae would be of different sizes? What possible reason? Extra space might always be nice; or perhaps space for a visiting patrol? But soldiers will always use extra space...

The idea of a larger ca. 40 - 42 strong turma is older than the excavations in Heidenheim, which seemingly provided proof. It can already be found in "The auxilia of the Roman Imperial Army" by Cheesman where he is again citing Von Domaszewski "Die Rangordnung des römischen Heeres". It was repeated in various publications since. Basically the idea is that an Ala milliaria with 24 turmae can only have around 1000 soldiers with larger turmae. He quotes an inscription from Coptos, CIL III 6627, describing the composition of a vexilation. Among soldiers from other units there are 424 equites from 3 Alae with 5 decurions, 1 duplicarius and 4 sesquiplicarii sugessting that each of them commanded around 42 men. The 12:9 ratio of rooms in the barrack blocks is exactly what is needed to get around 1000 instead of 720 - 768 troopers.
Since the elite first cohort contained 5 double strength centuria it seems plausible that the subunits of the elite milliaria alae were also bigger, with the argument that the elite soldiers could be effectively commanded by less officers than the ordinary men.

B.t.w. M.P Speidel also argues for 30 men turma and against Vegetius in "The Framework of an Imperial legion", Carlaeon 1992. I don't have this but it might be worth to cheeck his arguments.