Auxilia Cohorts and the Claudian Invasion of Britain

[Paullus Scipio]

D. Campbell wrote:

It's worth noting that we don't actually know what regiments took part in the invasion, so it's really a matter of which regiments could have taken part, might have taken part, are likely to have taken part ...

Tim Edwards wrote:
Jasper - I don't have this book. If you have a copy on your shelves I'd be very greatful if you could dig out the relevant info.

It's a useful book, but it's now 27 years old! You'd be better with Michael Jarrett's "Non-legionary troops in Britain (Part One)", Britannia 25 (1994). Paul Holder writes that only two regiments are directly attested as taking part in the invasion: ala I Thracum and ala I Hispanorum. Strictly speaking, we don't know that ala I Thracum took part, but it's a good bet, based on early inscriptions from Cirencester (RIB 109) and Colchester (RIB 201). By ala I Hispanorum, Holder presumably means the ala Vettonum (which appears as Hisp Vett on RIB 403). One of its commanders recorded that he had been highly decorated as "praefectus equitum alae I Hispanorum in Britannia" (ILS 2730), so presumably during the invasion.

As Duncan says, it is pretty much deduction and guesswork as to the units of the invasion force.Hard evidence is lacking...Holder also adds that the presence of the Batavian cohorts is "reasonably certain". The Ala Indiana, Cohortes I and VI Thracum and other units may have arrived as re-inforcements following the Boudiccan revolt of AD 61 ( 2,000 Legionaries, to build up Legio IX - badly mauled under Petilius Cerialis (Tac. Annals XIV.31) - 2 Alae and 8 Cohorts were moved from Germany as re-inforcements (Tac XIV.37). Holder also adds that the presence of the cohortes Delmatorum and Gallorum were among these re-inforcements as being 'reasonably certain' due to them not being known elsewhere, and attested on the Rhine previously.

Graham wrote:

As Duncan say's, very little for any unit in the invasion force. The only unit known is Legio II Augusta and that is only due to a mention in the career of Vespasianus.

Tactus confirms that Legiones II, IX, XIIII, and XX were the garrison when the Boudiccan revolt broke out in 60 AD. These were therefore "almost certainly" in the invasion force ( unless one or more had been rotated in to replace original invaders - and there is no evidence for such a rotation that I know of), and of course the invasion force may have been larger, with other legions being withdrawn after initial success. The evidence would be in the locations of various units at this time, as best as can be reconstructed. Tacitus gives the number and distribution of Legions in 23 AD, and it is possible to track changes thereafter - two Legions seem to have been raised, possibly by Claudius, but more likely by Caligula, (Legiones Primigeniae ), certainly fairly early in the reign of Claudius 27 Legiones are known. The invasion force is believed to have consisted of the four Legiones referred to above, three taken from the Rhine and IX Hispania from Pannonia, possibly augmented by several vexillations ( an inscription refers to a vexillatio from VIII Augusta, while an un-named Tribune of V Alaudae received decorations from Claudius, possibly for service in Germany, but perhaps more likely Britain [Dess. 2701 and 974], and we can track the movements of other Legions to replace the invasion force. We can be reasonably confident, then, that the core of the invasion force was the four Legiones referred to. D