As a medievalist, 476 C.E. is arguably the beginning date of my time period, the Middle Ages. That is the date we normally give for the fall of the Western Roman Empire, although it is chosen somewhat arbitrarily, as Rome was not really functioning as an empire by that point.
Which, I think, is not how people understand the fall of the Roman Empire. The great and powerful empire didn’t just get overrun one day, It was a slow, steady and somewhat predictable decline over a span of three centuries. In other words, it took longer for Rome to fall then the United States has existed as a country.
The Five Good Emperors
Rome reached the height of its power during the century-long reign of the Five Good Emperors, ending with Marcus Aurelius. The first four emperors had no biological sons, so they adopted highly capable men and prepared them for rulership. Aurelius, however, had a son decidedly lacking in ruling talent. This lackluster emperor, bearing the unfortunate yet somewhat appropriate name of Commodus (of Gladiator fame), was more interested in his own glorification than the well-being of the empire, and was eventually assassinated. Past that point, rulership fell more and more into the hands of career soldiers who simply could not offer well-rounded rule.
As an Aside: Contrary to Gladiator, Marcus Aurelius never attempted to turn the Roman Empire back into a republic. He was also not murdered.
The Fifty Wretched Rulers
By the third century C.E., would-be emperors were knocking each other off at such a rate as it was difficult to tell who the actual emperor was. It’s commonly known as the Third Century Crisis, although my medieval mentor always called it the Fifty Wretched Rulers, when, over a 50 year period, some 50 men vied for the position, and absolutely none of them died of natural causes.
Countries can only survive bad leadership for so long. The economy collapsed. The army became too inefficient to hold back a new threat: invading Germanic tribes. Various areas effectively pulled away from the Empire, seeing no reason to support an entity that was no longer supporting them. And the problems just fed on one another. The worse the economy, the harder it is to pay your soldiers Without soldiers, invaders continue to destabilize, causing more hardship. With more hardship comes the urge to pull away and strike out on one’s own.
And, remember, this is only the third century. We don’t property stick a fork in the Western Roman Empire and declare it done until the fifth. It’s a loooooong decline.
West vs. East
People talk about the “decline and fall of the Roman Empire” (from a historical book by the same name), but what we’re really talking about is the fall of the Western Roman Empire. Shortly after the end of the reign of the Fifty Wretched Rulers, a fairly capable emperor divided the empire into two halves, each with its own emperor, hoping to make administration more efficient for both halves, although it’s notable he decided to rule the Eastern half, as opposed to the half that contained the city of Rome.
The plan only half worked. The Eastern Roman Empire remained relatively strong, eventually becoming known as the Byzantine Empire and lasting until 1453. The rich and powerful fled eastward, taking their resources with them. The Western Roman Empire went into a long, slow death spiral ending in 476.