The Decline of Rome and Rise of Byzantium
Rome's decline accelerated due to a perfect storm of problems: political instability, military conflicts, and economic crisis. Emperor Diocletian 245−316CE tried to fix things by governing as an absolute ruler, dividing the empire into eastern and western regions, standardizing coins, and fixing prices to control inflation. These measures helped temporarily but couldn't save Rome in the long run.
Later, Constantine the Great briefly unified both halves of the empire and made three crucial changes: moving the capital to Byzantium (renaming it Constantinople), converting to Christianity, and ending Christian persecution. After his death, however, the western empire again declined.
External threats delivered the final blows. The Huns from Central Asia, led by Attila, attacked with 100,000 troops and raided over 70 cities. Though they failed to capture Rome or Constantinople, they weakened Roman defenses. Then Germanic tribes moved in, looting Rome in 455 CE.
History Snapshot: In 476 CE, a Germanic king forced out the last western Roman emperor, marking the official end of the Western Roman Empire!
The eastern half continued as the Byzantine Empire until 1453, but western Europe entered what's often called the "Dark Ages." Europe fractured into dozens of small kingdoms without written laws, literacy declined, economic systems deteriorated, and great construction projects ceased.