Western Roman (Civ5)/Civilopedia

After decades of warfare along the borders and economic crises, in 293 AD Emperor Diocletian created a new administrative system for the Roman Empire. He created a dual emperorship, selecting Maximian to oversee the western portion. Upon the abdication of Diocletian and Maximian, in 330 Constantine the Great founded Constantinople as a "second Rome." Theodosius I was the last to rule over an undivided empire; upon his death in 395, he bequeathed imperial rule to both his sons, Arcadius in the East and Honorius in the West.
Compared to the Eastern Empire, Rome in the West was less populous, fragmented culturally and politically, its economy in a shambles due to heavy taxation to maintain its frontier, and beset by barbarians. In 402 AD its administrative capital was transferred to Ravenna, although the economic and cultural center remained Rome itself. Until the 4th Century, its military had concentrated in northern Gaul and along the Rhine, but increasingly military resources had to be diverted to secure Italy, which led to further revolts and civil wars in Britain, Gaul, north Africa and Germania.
In a cycle of usurpers and mediocre emperors following Honorius, central power eroded and Rome gradually lost control of its provinces. Roman institutions collapsed in regions of Iberia and Gaul as the migration of barbarian tribes such as the Goths and Vandals brought new client kingdoms into being. With the Vandal conquest of Africa, the empire lost control of the western Mediterranean, accelerating the decline of trade and, more significantly, the vital grain shipments to Italy. Meanwhile, the Huns were unified under Attila in 444 AD, who promptly invaded Western Rome, wreaking havoc until his death in 453.
For the next 20 years Rome suffered a series of civil wars, culminating when the Germanic-born Roman general Odoacer deposed Romulus Augustus, the last emperor of Western Rome in 476 AD. Although the Emperor of the East Zeno recognized Odoacer's "Kingdom of Italy," the Byzantines sponsored an invasion by the Ostrogoths in 489. Theodoric, leader of the Ostrogoths, led his force into Rome in March 493 and slew Odoacer while they dined together. The fall of Rome in the west was complete. Despite a brief period of reconquest by Byzantium in the 6th Century, the Western Roman Empire would not return.