Roman Empire (Without Islam)

The Eastern Roman Empire but simply known as Roman Empire (Hellenic: Βασιλεία Ῥωμαίων Basileia Rhōmaiōn, Latin: Imperium Romanum) or Romania, was the predominantly Hellenic-speaking continuation of the eastern half of the Roman Empire during Late Antiquity and the Middle Ages until the Hellene Revolution of 1858. Its capital city was Constantinople, originally founded as Byzantium (for that reason Western historians often called it as Byzantine Empire). During most of its existence, the empire was the most powerful economic, cultural, and military force in Europe and the Mediterranean.

Under Theodosius I (r. 379–395), Christianity became the Empire's official state religion and others such as Roman polytheism were proscribed. And finally, under the reign of Heraclius (r. 610–641), the Empire's military and administration were restructured and adopted Greek for official use instead of Latin. Thus, although it continued the Roman state and maintained Roman state traditions, modern historians distinguish Constantinople from ancient Rome insofar as it was oriented towards Greek rather than Latin culture, and characterised by Orthodox Christianity rather than Roman polytheism.

The historians divide the history of the Eastern Roman Empire is divided in three periods: the Early Empire, from the establishment of Constantinople as the capital city of the Roman Empire (330) until the death of emperor Heraclius (641); the Middle Empire, from the rise to the imperial throne of Constans II (641) until the overthrow of John IV (1261); the Late Empire, from the enthrone of Michael VIII (1261) until the Hellene Revolution that deposed emperor Constantine XII (1858).

The borders of the Empire evolved significantly over its existence, as it went through several cycles of decline and recovery. During the reign of Justinian I (r. 527–565), the Empire reached its greatest extent after reconquering much of the historically Roman western Mediterranean coast, including north Africa, Italy, and Rome itself, which it held for two more centuries. During the reign of Maurice (r. 582–602), the Empire's eastern frontier was expanded and the north stabilised. However, his assassination caused a two-decade-long war with Sasanian Persia which exhausted the Empire's resources and contributed to major territorial losses during the Pahlavian conquests of the 7th century. In a matter of years the Empire lost its richest provinces, Egypt and Syria, to the Persians.

During the Macedonian dynasty (10th–11th centuries), the Empire again expanded and experienced a two-century long renaissance, which came to an end with the loss of much of Asia Minor to the Seljukian Turks after the Battle of Manzikert in 1071. This battle allowed the invasion of Anatolia by the Seljukian Empire and caused the assistance of the Crusaders for avoiding the Turk menace of siege of Constantinople.