Hey all,
This topic has always interested me, as I just find it so amazing that an empire like the Romans' could collapse so fast in the 4th and 5th centuries AD. I am just wondering what you all think was the cause of it. DISCLAIMER: Sorry if this topic has been done before!
As for myself, I think Hadrian i in certain part to blame for it. I am fascinated by the Roman Army in every way, but I think what Hadrian did with it was what eventually led to Rome's decline. Allow me to explain. (And I am not saying Hadrian was a poor emperor, I actually think he was one of the better ones, but I think his military policy was what started Rome's decline.)
Hadrian followed Trajan as emeror, and as we all know, Trajan was quite the military emperor. He conquered Dacia and was the only Roman Emperor to reach the Persian Gulf. But when Hadrian takes over, he decided that Rome should assume a defensive policy as far as expansion was concerned, and consolidate what it had gained. He fortifies the British frontier (Hadrians Wall, duh) and the Rhine frontier. He, imho, is the guy who takes the bite out of Rome's military, and his reforms make Rome a RE-actionary and not an offensive weapon. With Rome's armies as great as they were, I feel Rome could have expanded much farther, another topic of debate, a great thread to be sure, but Hadrian kind of said "No, we're happy with what we;ve got." In years and emperors after Hadrian, his trend generally continues (the great exceptions being Marcus Aurelius and a few others) and Rome's military is on the defensive. This doesn't necessarily make them soft, but it does make them less of a potent force. Of course Rome would never have fallen without the political struggles inside it and other key factors, I just find the lapse in military readiness that develops over a century of defensive policy to be what allowed the many barbarian nations that beset Rome in the 4th century AD to take the empire apart piece by piece, although certainly the ineffectual political situation and leaders did much to help this situation.
As Napoleon said: "The only logical end to a defensive strategy is defeat!" (sorry if that's not the exact wording, but you get the idea!
Anyways, your thoughts!