heavy cavalry engaging heavy cavalry

[Flavivs Aetivs]

Oeps, sorry Evan, mixed them up. My objection is the same, these are very unyielding things and impossible to fire singlehanded (I have fired one at the LRE). So the introduction of pistols is totaly silly AND we have NO iconographic or written proof of cavalry in Roman era having used the crossbow.
I do agree with the moderation by Robert, as any time there is any discussion on cavalry, it seems a scant few of our esteemed members cannot control their hero worship of the grand Polish hussars or the glorious knights in shining armour and things get derailed at great speed. Moi makes an excellent point on the stirups, by the way.

Moi indeed does make an excellent point.

The stirrup is applicable to Roman cavalry in the 5th-6th centuries, Its debatably believed Aetius introduced the stirrup from the Huns (whom may have had stirrups - its still debatable) because he was the last one with a long enough and stable enough administration to implement the change. However it is still unlikely.