From Wikipedia

Rome

Episode Six

The Fall Of The Roman Empire

The decline of the Roman Empire is one of the events traditionally marking the end of Classical Antiquity and the beginning of the European Middle Ages. Throughout the fifth century, the Empire's territories in western Europe and northwestern Africa, including Italy, fell to various invading or indigenous peoples in what is sometimes called the Migration period. Although the eastern half still survived with borders essentially intact for several centuries (until the Arab expansion), the Empire as a whole had initiated major cultural and political transformations since the Crisis of the Third Century, with the shift towards a more openly autocratic and ritualized form of government, the adoption of Christianity as the state religion, and a general rejection of the traditions and values of Classical Antiquity. While traditional historiography emphasized this break with Antiquity by using the term "Byzantine Empire" instead of Roman Empire, recent schools of history offer a more nuanced view, seeing mostly continuity rather than a sharp break. The Empire of Late Antiquity already looked very different from classical Rome.

The Roman Empire emerged from the Roman Republic when Julius Caesar and Augustus Caesar transformed it from a republic into a monarchy. Rome reached its zenith in the second century, then fortunes slowly decline (with many revivals and restorations along the way). The reasons for the decline of the Empire are still debated today, and likely multiple. Historians infer that the population appears to have diminished in many provinces—especially western Europe—from the diminishing size of fortifications built to protect the cities from barbarian incursions from the 3rd century on. Because these fortifications were restricted to the center of the city only, some have suggested that parts of the periphery were not inhabited anymore.

By the late third century, the city of Rome no longer served as an effective capital for the Emperor and various cities were used as new administrative capitals. Successive emperors, starting with Constantine, privileged the eastern city of Byzantium, which he had entirely rebuilt after a siege. Later renamed Constantinople, and protected by formidable walls in the late fourth and early fifth centuries, it was to become the largest and most powerful city of Christian Europe in the Early Middle Ages. Since the Crisis of the Third Century, the Empire was intermittently ruled by more than one emperor at once (usually two), presiding over different regions. At first a haphazard form of power sharing, this eventually settled on an East-West administrative division between the Western Roman Empire (centered on Rome, but now usually presided from other seats of power such as Trier, Milan, and especially Ravenna), and the Eastern Roman Empire (with its capital initially in Nicomedia, and later Constantinople). The Latin-speaking west, under severe demographic crisis, and the wealthier Greek-speaking east, also began to diverge politically and culturally. Although this was a gradual process, still incomplete when Italy came under the rule of Barbarian chieftains in the last quarter of the 5th century, it deepened further afterwards, and had lasting consequences for the medieval history of Europe.

Throughout the fifth century, western emperors were usually figureheads, while in the eastern emperors managed to secure their independence from influential military leaders. For most of the time, the actual rulers in the West were military strongmen who took the titles of magister militum, patrician, or both, such as Stilicho and Aetius. Although Rome was no longer the capital in the West it remained the West's largest city and its economic center. But the city was sacked by rebelled Visigoths in 410 (for three days) and later again by the Vandals in 455 (for fourteen days), events that shocked the contemporaries and signalled the disintegration of Roman authority. Saint Augustine wrote The City of God partly as an answer to critics who blamed the sack of Rome by the Visigoths on the abandonment of the traditional pagan religions.

In June 474, Julius Nepos became Western Emperor but in the next year the magister militum Orestes revolted and made his son Romulus Augustus emperor. Romulus, however, was not recognized by the Eastern Emperor Zeno and so was technically an usurper, Nepos still being the legal Western Emperor. Nevertheless, Romulus Augustus is often known as the last Western Roman Emperor. In 476 after being refused lands in Italy, Orestes' Germanic mercenaries, led by the chieftain Odoacer, captured and executed Orestes and took Ravenna, the Western Roman capital at the time, deposing Romulus Augustus. The whole of Italy was quickly conquered and Odoacer was granted the title of patrician by Zeno effectively recognizing his rule in the name of the Eastern Empire. Since, as a barbarian, he was not allowed the title of Emperor, Odoacer returned the Imperial insignia to Constantinople and ruled as King in Italy. Following Nepos' death Theodoric the Great, King of the Ostrogoths, conquered Italy with Zeno's approval.

Meanwhile, much of the rest of the Western provinces were conquered by waves of Germanic invasions, most of them being disconnected politically from the East altogether and continuing a slow decline. Although central authority in the West had been lost, Roman culture would last in most of parts of the former Western provinces into the sixth century and beyond.

The first invasions had disrupted the West to some degree, but it was the Gothic War launched by the Eastern Emperor Justinian in the sixth century, and meant to reunite the Empire, that eventually caused the most damage to Italy, as well as straining the Eastern Empire militarily. Following these wars Rome and other Italian cities would fall into severe decline (Rome itself was almost completely abandoned). A last blow came with the Persian invasion of the East in the seventh century, immediately followed by the Muslim conquests, especially of Egypt, which curtailed much of the key trade in the Mediterranean on which Europe depended.

The Empire was to live on in the east for many centuries, and enjoy periods of recovery and cultural brilliance, but its size would remain a fraction of what it had been in classical times. It became an essentially regional power, centered on Greece and Anatolia. Modern historians tend to prefer the term Byzantine Empire for the eastern, medieval stage of the Roman Empire.