
Apparently, the highlanders had not been trained to deploy into the textbook square formation, so they stood two-deep and fired at the approaching enemy. The cavalry veered off, rather than engaging them.
It is a commonplace that cavalry will not attack a formed line of infantry. There seem to be two reasons. First, the cavalrymen themselves are unwilling to enter a killing zone, the area in which (in nineteenth-century warfare) they might be peppered with shot or (in ancient times) deluged with arrows and sling bullets. But second, horses are naturally averse to crashing into solid barriers, so that, faced with an unflinching line of infantry, they will normally attempt to go around it. Only the fortuitous breaking of the infantry line would give the cavalry an avenue through the barrier, rather than around it.

A barrage of missiles was planned to dissuade any of the Alans from loitering in the killing zone, while measures were put in place to tackle the horsemen as they inevitably veered off. The main point is that a completely cavalry army could be handled, if not easily, then certainly straightforwardly. Cavalry on its own had very limited utility.
Nevertheless, there is a widespread belief, ingrained from generations of repetition, that — sometime in the late AD 250s or early 260s — the emperor Gallienus developed a solely cavalry army, which the German scholar Robert Grosse dubbed the “battle cavalry”.
Gallienus’ cavalry commanders?

So how might we expect these “changes” to manifest themselves? Surely Dr Waldron has more than a gut feeling to justify planting the seed of doubt in readers’ minds. Surely he won’t simply restate “facts” that I already dealt with in the book. Surely?
Chiefly, Dr Waldron claims that “various cavalry commanders in this period eventually became emperors or usurpers”, by which he means four individuals, none of whom is ever called “commander of the cavalry army” or “commander of the battle cavalry”. But each individual’s link to cavalry, however tenuous, is reinterpreted in a subjective way in order to fit the theory of the (unproven) “battle cavalry”. Here are the four men.
1) Aureolus
When Zosimus introduces Aureolus in his description of the events surrounding Gallienus’ death at Milan in AD 268, he describes him as “commander of all the cavalry”. In this regard, we should remember the pertinent observation made by Matthias Springer in his 1988 paper, that the phrase “commander of all the cavalry” is essentially meaningless. (“Only a preconceived opinion”, wrote Springer, “can infer the existence of a special battle cavalry from that phrase”.) After all, it was the emperor himself who commanded all the cavalry, and he did so through the agency of his equestrian officers.However, the phrase makes perfect sense in the context of a battle, where the cavalry forces might be entrusted to an overall commander, such as the one Septimius Severus explicitly appointed at the Battle of Lugdunum (as I explain in the book). Aureolus, we know, had commanded the cavalry at Mursa against the usurper Ingenuus, because Zonaras tells us so.
Dr Waldron complains that, at the Battle of Mursa (which probably occurred in AD 260), “Zonaras does not speak of ‘all the cavalry’ (Gallienus led the Mauri)”, which is perfectly true. In fact, Zonaras tells us that “commanding the cavalry, Aureolus, by fighting nobly with his horsemen, destroyed many of those who sided with Ingenuus, and turned the remainder to flight”. I think most of Zonaras’ readers would realize that he must have been directing all the cavalry forces present in the battle with the exception of those accompanying the emperor.
Eight years later, Aureolus had moved on with his career, but his claim to fame was having commanded the cavalry and won the day for his emperor at Mursa, the first battle against a usurper. Let us not lose sight of this important fact, which is often forgotten in the headlong rush to try and “prove” the existence of Robert Grosse’s “battle cavalry”.

2) Aurelian
Zonaras records that the future emperor Aurelian “came to (Gallienus) with horsemen” in the struggle against Aureolus in AD 268. (I wondered, in my book, whether this might have been Gallienus’ horse guard, but the phrase is too vague to press the point.) The only other testimony comes from the rather unreliable “Life of the deified Aurelian” in the Augustan History, which claims that “before he took power, Aurelian commanded all the cavalry under Claudius”. (Here is this meaningless phrase “all the cavalry” again, and I wonder whether this, too, might have been a battlefield command.)3) Claudius II

Dr Waldron is (naturally) not alone in creating this spurious link between cavalry — any cavalry — and the fictitious “battle cavalry”. For example, Lukas de Blois, who has championed Gallienus’ cavalry army for fifty years, describes Claudius II (in his 2019 book) as “Gallienus’ cavalry commander” and “the commander of Gallienus’ new army”. He wasn’t.

4) Probus
Dr Waldron also highlights the fact that the future emperor Probus “according to the Epitome de Caesaribus was named Equitius”. Like the previous three individuals, Probus was already discussed and dismissed in my book, but perhaps Dr Waldron overlooked that passage.Equitius, we should note, is not an unknown Roman nomen, so — giving the Epitome the benefit of the doubt — it may well have been Probus’ own name before he took the official nomenclature of Marcus Aurelius Probus.
Incidentally, it is quite unlikely that Aurelius Victor (the ultimate source of the Epitome), writing almost a century after the reign of Probus, was aware of the curious coins (discussed in my book) that each carry one of the letters A, E, Q, V, I, and T; and equally unlikely that he drew the same conclusion as Alfred von Domaszewski, that this was a coded reference to “Equitius” as the emperor’s name.
In any case, it’s a curious argument that concludes, from a horse-related knickname found on only one occasion (equus means “horse”, so Equitius ought to mean “pertaining to horses”, so the argument goes), that Probus must have been not only a cavalry commander, but specifically in command of the alleged “battle cavalry”.
5) Diocletian?
Lastly, Dr Waldron throws in a fifth individual: “It may be relevant that Diocletian was a Dalmatian career soldier”. I simply cannot imagine how this is supposed to bolster a case for the existence of a “battle cavalry”, so I’ll leave that one.Cavalry coins indicating a reform?
But finally on this theme, Dr Waldron supports his belief in Gallienus’ cavalry reform by observing that “numismatic legends and iconography attest to periods in the late third century when cavalry was especially important”. Forgive me my deep scepticism as we explore what he means.
Here is the reverse of a coin of Galerius, depicting that fourth-century emperor on horseback trampling his enemies. It wasn’t a new motif. Septimius Severus had used it, a century earlier. Severus Alexander, Decius, and Gallienus, too.
But many emperors appear on their coinage riding a horse when the theme is the emperor’s ADVENTVS (“arrival” in Rome). Hadrian used the same motif on his ADVENTVS coins. Likewise, Gordian III, Philippus, Decius, Trebonianus, Claudius, Aurelian, Probus, and Carus (amongst third-century emperors).
When Septimius Severus appeared as a galloping horseman, the theme was obviously the emperor’s VIRTVS (“manly courage”). Nobody would have suggested that it was an indication that the emperor had made some kind of change to the cavalry.
Let’s try and rein in some of these wild unsupported allegations of “changes to the cavalry” under Gallienus.