Cataphracts development

[Nicholas Gaukroger]

I think that the earliest use of Seleukid catafracts may be Panion which was around 200BC IIRC.

It would appear likely that Antiochos III was influenced to develop his catafracts by his experiences during his great eastern expedition. That is the most likely time he would have come into contact with users of catafracts such as the Parthians. Before that use of horse armour was partial and really only amongst the steppe or near steppe people such as the Baktrians recorded at Gaugamela.

It does seem fairly clear that the catafract was a steppe development and so is likely to have been a response to horse archery as people have stated. It is not clear why Antiochos would adopt the catafract unless he was either impressed by them (they must have looked impressive) or perhaps had an eye to his eastern neighbours and their obvious intent to take over Seleukid territory.