Grossbottom, back off.
You are spending nearly as much time in not-quite-over-the-line insults as you are in actually asserting or defending your position.
You will find that such posting is not persuasive to either opponents or neutral observers, but it is persuasive, of a different point, in regards to the SDMB staff.
EVERYONE needs to refrain from personal remarks, as well.
[ /Moderating ]
Interesting point. Maybe someone could answer this:
Say I’m a heavy cavalryman, and I attempt a full-on charge into massed infantry:
1.) If I succeed, what am I doing? Am I hacking at people, trying to trample them, what? Am I going to be able to hang out and wreak some carnage for a bit, or will my horse’s momentum tend to carry me through? Do I even want to hang around, or would I rather just gut a few peasants, gallop on out, and do it again?
2.) If I fail, what happens? Do I just die horribly, or is there some plausible way for me to survive a botched charge?
Grossbottom, I don’t know if this is a rule violation for me to say or not, but your tone and tactics make you look like Comic Book Guy’s more annoying, less socially-adept little brother. Seriously, get off your (pardon the pun) high horse. You both have valid points, neither of which are really relevant to the overall debate proposed by the OP.
In terms of a one-on-one battle, 100AD Roman army vs. 400AD Roman army, I’m not sure. I thought Trajan held the largest portion of land Rome ever held, and his army was huge, but according to wikipedia by 400AD the army was comparable in size and discipline was returning. I really think it would come down to which side had better discipline and morale than differences in arms. Of course, all the myriad circumstances of terrain, weather, hunger and so on could be the deciding factor, so who knows.
Your purpose is to break the line. Disciplined infantry that hold formation are brutally hard to defeat, so cavalry and archers are the tools developed to combat what started way back in Greece and was perfected by Rome. Break the lines, you get the men apart enough to run in and hack away. If they hold, you smash against them and die trying to weaken their forces. War is about attrition, and the psychological effects that can have on those men (and rare few women) who are asked to stand in line and fight for someone.
So you could go in and hack and trample, but only usefully if you break the line first, get through the pikes or spears or whatever, and force the formation to break up. Otherwise, carrying through, you make take some cheap-to-fund and easy-to-replace infantry out, but you will probably lose a really expensive horse and weapons and armour in the process.
This was not an explicit rules violation, but in light of the Mod note posted 17 minutes earlier, it was a really bad idea.
EVERYONE drop the personal comments.
[ /Moderating ]
To bring the debate full circle, and back to the original OP: the reason why the debate about heavy cav tactics is somewhat-relevant, is that one of the differences often cited between the army of 100 AD and that of 400 AD is the increased importance of the use of heavy cav. by the Romans.
What to make of this development, in terms of the relative ability of the late vs. early army?
On the one hand, it diversified the "tools’ in the hands of late republican generals. This has to be a plus in terms of their ability to react to different situations.
On the other hand, it may simply be a sign of decline: that their opponents (frequently, other Romans in civil wars) were simply less disciplined and thus comparatively more vulnerable to the use of heavy cav, making its use more attractive. If true, this may indicate that the late army is overall less effective.
Neither, Imho.
They started using more cavalry for at least two important reasons, and is not as much the increase in heavy cavalry as in light cavalry.
Primarily because the enemies had more cavalry, so you need heavy cavalry on the battlefield. But the proportion of heavy barbarians is not that high, usually just the nobles.
Secondly. Someone upthread said you can’t hold terrain with cavalry. This is absolutely untrue.
Cavalry is much much much more mobile and can roam around large areas of the countryside at will, if the is no other cavalry to stop them.
This is what Rome faced once barbarians broke through the limes, roaming plundering bands in the hinterland. Cavalry is needed to contain them.
The late Roman army saw a large increase in light-cavalry of several types, horse rchers, dalmatae, mauri, scutarii and maybe the promoti were light too.
Yes those cataphracts are there, but they are few in number.
The devellopment later on is towards a dual-role cavalry man, reasonably armoured, armed with a lance but also equipped with the bow.
Fair enough; though the Roman army was as often used against other Romans, as against the barbarians.
But would this force in your opinion win against the Roman army of 100 AD?
Gotcha, my apologies. It often takes me a long time between starting a post and hitting submit because of various distractions.
As for the points Malthus and Latro made subsequently, yes, cavalry became more pervasive and numerous, but overall were they enough to overcome the tight, disciplined formations of Trajan’s forces? I wonder, given the notion presented earlier that the 100AD soldiers were in fact possibly better armoured, if the available cavalry of Honorius’ time would really be sufficient to break a solid infantry formation. I’m no expert, but I think they were still more of a mobile cavalry than shock troops on heavy horse, correct?
I just think that given the state of the empire at 400AD vs. 100AD, the straight up decline of morale, civil wars, and a succession of tyrants and barbarian hordes attacking wouldn’t make the later army less inspired than the earlier. I suppose there’s no right answer, in the end.
I allready gave my opinion on page 1 
Oh and by the time of Honorius it was long over.
In my view, the situation in west was lost by Theodosius. He still had a quite capable army, a very good one really. It was decimated in the religious war, if you might call it that, against Arbogast. Later when the Goths were plundering Italy he kept the army in it’s barracks while he prostrated himself in church, praying to god for divine intervention.
Due to this inactivity Italy was devestated and large parts of the west were now de facto independant from Roman authority. Rome was no longer in a situation where it could recover.
At Garcia Hernandez in the Peninsula War, Dragoons of the Kings German Legion broke two French squares (might have been three,relying on memory here) in close succession.
So it COULD be done, but I doubt very often.