We said last post (Revelation for Dummies 4) that a few maps would illustrate the point, the point being the fall into the Dark Ages for the Latin West, and the simultaneous flowering of the Eastern Greek Empire: here are some illustrative maps (Click on maps to enlarge):
The Empire was officially split into East and West with separate rulers back in 395 A.D., with the death of the last full Emperor, Theodosius.
From there things quickly got worse for the West, as individual nations rebelled and set up their own independent kingdoms, outside of Western or Eastern control. These political border changes were not peaceful, but were accompanied by wars, sacking and looting, rape, murder, and slaughter of various Western populations.
By about 530 A.D., the Western half of the Roman Empire was essentially nonexistant:
Parts of the West were recovered by Emperor Justinian the 1st, Italy and the Western part of North-Africa (Carthage, Morocco) and even the Southern tip of Spain, as well as the Alars in the North-East. Most of this happened between 533 and 536 A.D., but material gains were eroded again after Justinian's death.
The Eastern Byzantine Empire reached its peak extension in Justinian's reign, and he capped it off by building the Hagia Sophia, probably the greatest cathedral built until that time.
The first Major Bubonic Plague struck in 541-544 A.D., however, various smaller plagues had been running amok in the West for many years already as a result of war and famine.
Next the powerful Lombards invaded Italy from the north in 568 A.D., and took over most of the peninsula and all of Northern Italy. Their former territory was filled by the Avars. The Frankish Empire had expanded to absorb the Bretons on the West coast of France, and also the Thuringians and Burgundians. Later, in 560 A.D. the Slavic Bulgars invaded to attack the Greek city of Athens. Finally, even before the advent of Islam, the Ghasahid kingdom began to encroach upon most of Palestine, weakening the Byzantine hold on the Holy Land and Egypt.
The strength of the Eastern Empire was in its central position in over the Eastern Mediteranean, its Roman built roads, and sea power. But it never had the disciplined standing army of the old Roman Empire.
The maps illustrate clearly the relative poverty and collapse of the West, while the East continued to flourish, at least in the center of the Byzantine Empire. Although many smaller kingdoms rose out of the West, they were all local peoples simply getting independence by force.
In the next century saw rapid expansion of the Islamic Caliphates, with the losses by the Eastern Byzantines to the Arabs of Armenia, Syria, and Egypt. This effectively lost control of North Africa, and the defense of Spain also became impossible.