Quote Originally Posted by Uticensis View Post
The idea that the Roman legion was less disciplined in the later empire is a myth. Discipline did not decline, particularly not in the field army. In fact, since the time of Gallienus, officers were no longer senators who gained their commissions through family influence, but mostly men who worked their way up the ranks and knew how to train and lead men. The problem with the late Roman army was not its soldiers, but its government (which was breaking down, and often lacked the money, resources, and coherence to properly utilize the armies, and often wasted whole armies in bloody civil wars). And the fact that is was simply overwhelmed with enemies (just look at Stilicho- he was a brilliant general, but his regency ended in failure because he simply did not have the troops to hold every front)
This is only true to a point. The Late army was run via the Concillium, and it allowed the army itself to revolt when it didn't like the Emperor's orders. This is why Constantine dispanded the Guard, and why Justinian was forced to turn back when a standardbearer broke ranks and objected. The maniple dates from a time when the Roman soldier was expected to obey unwaveringly, to decimate his friends, and could thus be trusted with independant action to a degree.

I concede that I may have been wrong to say that the Spatha is too different from the Gladius, but I think its popularity came mostly from the influence of Germanic soldiers in the army.
Germans coming into the Auxillia were thougherly Romanised, the actual cause has more to do with the soldiers seeking to differentiate themselves from the populace, and thus deliberately adopting "barbarian" customs. Nonetheless, the Pompeii Gladius is a study in a sword-pattern designed to be produced by an idiot and still be useable. It's parallel edges do not cut as well as the earlier leaf-blade and it's point is not as fine.

I don't agree. Warfare had changed too much since the time of Alexander. Sassanid cavalry was a lot different from Achamenid cavalry. They used more horse archers (we've all seen these guys rip the slow moving phalanxes apart in EB) and cataphracts. The Romans developed military units and tactics designed to counter these threats. The Macedonian phalanx, on the other hand, was designed to fight the Persian and Balkan soldiers of five hundred years earlier.
The Persians were always known first and foremost as archers (hencer Herodotus saying young noblemen learned three things: riding, archery, and truth telling). The difference was in the heavy cavalry, for which the phalanx was much better suited.

Warfare also necessitated smaller, more mobile infantry units. That's why in the late empire the legions shrank to under 1000 men each, with other units, such as auxiliary units, being half that size. The phalanx would have been too big and clumsy. As I said, warfare had changed too much for the phalanx of Alexander's time to work. That's why, after Caracalla's death, you never hear of the Romans using it again.
The units were smaller after Constantine's time because this prevented a single general from garnering the loyalty of 12,000 odd men just sitting in barracks and not even on campaign. The smaller units and lack of concentration prevented the Romans from gathering the Legions to resist the mass incursions of the 4th/5th Century.

And the Macedonian phalanx would have been utterly useless on the empire's other major front, the Rhineland. I could just see the German tribesmen rolling on the ground in laughter as they watch a Roman army taking enormous spears and forming a Macedonian phalanx in that hilly, marshy, forested country.
While this is true, it would have been very useful in Northern Italy.

However, I don't understand where you get the idea that most of the failures of the later Empire are at least in part down to the Roman army being unable to receive and hold a cavalry charge, or to pin enemy infantry. What are some examples? The late Roman army did very well against the cavalry-dominated Persian army. The only example I can think of the Roman army really getting crushed by a cavalry charge is Adrianople, but in that case it is because the Goths used the old infantry/cavalry anvil/hammer tactic on them. In fact, cavalry could not be made to charge a well ordered late Roman infantry formation from the front. Hence, the importance of missile cavalry among Rome's enemies, who used them to pepper the Roman lines, hoping to break up the formation enough to get their horses to charge.

As for pinning enemy infantry, I can't think of this ever being a problem. The Roman army was very successful against infantry dominated armies (Franks, Alamanni, ect.) as long as there was Roman soldiers around to fight these people (unfortunately, often there were none, or at least very few, leading to the breakup of the Western empire). Do you have an sources for problems stemming from pinning infantry?
Look at the casualty numbers, winning isn't everything. Cunctator, Wellington, Washington, etc., will all tell you that. The pike block has endurance for a protracted and constant melee, the Roman system was best when they were able to rotate troops, and to retire and advance. This is why the spear became increasly popular. The army was no longer advancing, and it couldn't afford to retreat, so it had to hold.

In some instances a pike block would have reduced Roman casualties. A properly drilled pike block would have been mobile and resistant to both the infantry and cavalry the Germanic people had. After all, when your enemy get's good at what you're good at; you have to get good at something else.