The decline and fall of the Western Roman Empire
By the third century A.D. the Roman Empire was simultaneously beset by barbarian invasions, civil war and disorder.
Emperors had to fight to gain their throne and had to keep fighting to preserve it. The "Pax Romana" was crumbling. The barbarians were both within and without the walls. While still territorially intact, the Empire was decaying.
The army comprised mainly of barbarian mercenaries, not Roman citizens. Trade and agriculture were declining under the heavy burdens of civil war and taxation.
During the next century the Empire was divided into East and West halves. The Western Empire came to a brutal and bloody end in 476 A.D., when Odoacer became King of Italy.
After the foundation of Constantinople in the East, the destinies of the two halves of the empire split even more. Lacking the resilience and wealth of the east, the western empire decayed within a century of Constantine's death. The barbarian invasions of the 4th century were not a simple matter of Romans against outsiders. The barbarians, in particular the Goths, had enemies of their own, such as the Huns, who had built up behind them.
In 376 the Goths joined forces with the Romans to fight off the Huns. Since them, the armies that defended the frontiers, there were many barbarians if not more, as there were Romans. Though quite a number did become Romanised and were converted to Christianity.
This change in policy blurred the distinction between the civiliszd and uncivilized world and began the slow transformation of the western empire into a semi-barbarian state. It was not so much an invasion as a migration, a tidal wave of outsiders attracted by Mediterranean wealth. But the attractions were fast disappearing. Constant disorder led to the breakdown of law and order, the neglect of trade and the disintegration of the magnificent road system. Heavy taxation, the decline of educational standards and putting the army above all else, caused far-reaching social and economic changes.
Rome was finally sacked by the army of Alaric, chief of the Visigoths in 410 A.D. Thereafter Germanic generals were less interested in serving a throne that had lost its prestige.
In 451 A.D. an invasion by the Huns led by Attila again put the city under threat, but it was repelled. But in 455 A.D. the Vandals under Genseric sacked Rome.
In 476, the barbarian chief Odoacer deposed the last emperor, Romulus Augustulus. The fierce northern invaders, whom the early Romans had so often and so proudly defeated, were now the victor and the thousand-year reign of the city of Rome had ended. In the east, the Eastern Roman Empire continued as the Byzantine Empire, and would go on to endure for another thousand years, but it was essentially a Greek empire, whose rulers consistently looked eastwards, paying no more than lip-service to Roman ideals. Nevertheless, it did provide a shield against eastern invaders.
Odoacer was pronounced 'patrician' by the Byzantine Emperor and 'king' by his soldiers, ruled in Italy until he himself was conquered and deposed in 493 by Theodoric the Great, King of the Ostrogoths.
The strife and violence, invasions and deposed rulers would go on for a few centuries more and the might and glory that once was once the Roman Empire would only be found in stories and archaeological digs.