The Late Roman Army

[Aryaman2]

"The historical battles of the Muslim conquest and the Mongol conquests are very similar in pattern. There are standing armies, vast ones, but in general, its the horse raiders that are the principal force"

That is not true in the case of Muslim conquest, Muslim armies were in fact basically infantry, cavalry playing a very minor role, and no use of horse archers at all.

I think we are talking past each other. We are talking about different phases of conflict.

The long series of exchanges between Mekkah and Medina are essentially calvary exchanges until Mohammed conquers Mekkahh outright with a combination of calvary and more conventional sources. When they march against the Byzantines, the first exchanges are almost always calvary exchanges, but you are right, when the cities fall, it's to infantry.

I never argued that muslims had horse archers or that cities fell to horse calvary, that's seigecraft and a different matter altogether. Seige warfare is entirely different.

When I say "principal" force I am not talking numbers either, but significance in strategy and tactics. Just like we have relative few aircraft carriers, but they are still the heavy hitters.

As for the Parthians themselves, there is an open discussion over if the kataphraktoi they fielded did use bow or just lance. Judging from historical examples, it is very difficult to maintain a force of armored horse archers, for instance both the Sassanian and the late Roman armies used mercenary horse archers from nomadic people, but when those were not available the use of horse archers decreased and even ceased completely, by the time of the muslim conquest the Byzantine Kataphraktos was again basically a lancer, and the Persian cavalryman reverted to the use of javelins rather than bow. The horse archer is a product of a way of life, to have them you either are nomadic people or have a full time training force, like that of the Mameluks in a later period.

I agree that there is a decrease in horse archers, but I don't think that is due to a lack of nomadic lifestyle. I think that horse archers originate there it's true, but it's obvious that the Sassanians could have trained and maintained the tradition without them. IMO they decrease in number and significance exactly for the reasons I mentioned, that they were effectively countered by a heavy calvary on the part of the Late Roman army.

This started with the discussion that there is an increase in calvary, not just in number, but also in its role and importance in the Late Roman Army. Then the discussion moved, suggesting that the calvary could not have been very significant after all. I think that that's an inherently counter-intuitive response. Instead of trying to think of why the calvary couldn't work, we should think of ways how it could have worked, since its obvious that they made that change. I'm just offering speculation as to how that could have happened.

I still think you picked the wrong example with Muslim conquest, not only in sieges, but also in field battles, like Yarmuk, infantry was the main force, cavalry was used basically to execute the routed enemy.

On the Late Roman Army, I think the reson for more cavalry was, as you suggested, to counter the Sassanians. The Roman heavy cavalry was fully armoured not so much as heavy cavalry as a protection against arrows. However, I don´t think that was the final solution against horse archers, and whenever they could the Byzantines hired horse archers and tried (unsuccesfully) to train their Kataphraktoi as Horse archers.. The solution was, as always, combined arms.
So, to sum up my position, yes the Romans increased their cavalry to fight Sassanians, because cavalry was very effective in battle, but not because it was strategically more mobile.