The fall of the roman military power

[Robert Vermaat]

I think you are understimating the huge difference between the Huns and other mounted archers. The Huns were pushing tribe after tribe for a Century before Attila, and quite effectively, at that.

Sure, they did that, but that had happened time after time with many tribes before them. By itself, it's not a sign of Hunnic invincibility. It's a common nomadic treat - if your enemy wants your land you fight, if you loose you move away.

When Rome fought against the Huns, the limitanei were always defeated, even the minor incursions

No, i don't think you can put it just like that. For one, the limitanei were never intended to deal with full-scale invasions. The Limitanei were there to guard the borders, deal with raids, stay in contact with the enemy. their static role and relative small numbers dispersed along the border made it impossible to deal with any full-scale invasion. However, when such an invasion was being dealt with by the Comitatenses, the Limitanei were usually involved in such a campaign.
Nor were the Huns never defeated. Back in 408 an invasion was dealt with. After that, for a long time they were allies of Rome. It was not until Attila became their leader when they became a major threat to the Empire. For a long time they were bought off. But after Attila's death, they never were a major threat again.

Again, only the huge (in political terms, if not in numbers) army mustered by Aetius against Attila in the 451 campaign managed to defeat them, and mostly because the Visigoths and Burgundians had developed their military capabilities and Aetius knew Hun tactics and methods very well (the same way the Huns learned from him and the Romans the siege techniques they used later to run over Europe). All the other Roman armies, posts and towns in the 451 and 452 campaigns surrendered or were duly defeated by them.

Visigoth and Burgundian armies were not the reason the Huns were defeated, there are no real signs of them becoming more of a military threat. It usually was Roman generalship that made the difference, so my point would be that Aetius managed to (just!) outgeneral Attila.

The Huns were nomadic archers, with bows much more powerful than Europe had ever seen ( http://en.wikipedia.org/wiki/Hun_bow ), and probably superb horsemanship (was it Apollodorus who said they did everything on their horses?) which proved an unbeatable combination once the small warbands were united by a strong leader.

I have not heard any reason why the Huns would have been better horsemen than, say, the Scythians or the Parthians.