HistoryFrom 330 to 476, the Byzantine Empire was known as the "Eastern Roman Empire", as it was effectively a half of the Roman Empire that covered the eastern portions. Constantine the Great moved the capital of Rome to the old Greek city of Byzantium, which he renamed Constantinople in his honor and built into a great city. The Eastern Roman Empire outlasted the Western Roman Empire, which fell to barbarian invasions in 476 AD. The Byzantines were also attacked by outside tribes at the same time, but they never lost much ground to them.
The Byzantines referred to themselves as Romans at first, but the empire progressively became more eastern in its culture and religion. Christianity split into Catholicism (the Latin Church/Chalcedonian Christianity) in the west and Eastern Orthodoxy (the Greek Church) in the east, and the Byzantine empire appointed its own religious heads, the Ecumenical Patriarchs of Constantinople, rather than following the Pope in Rome. The Byzantines enjoyed tranquility while the Germanic tribes in the west fought each other, but they had on-and-off wars with the Sassanid Empire of Persia and Mesopotamia to the east, the Huns to the north, the Goths and Vandals to the west, and the Arabs to the south. Emperor Justinian (r. 527-565) began a project to reconquer the Western Roman Empire from the Germanic tribes, and his generals conquered North Africa, southern Spain, and Italy from the Vandals and Goths. However, these gains were negated after the death of Justinian, as the Lombards invaded Italy in the 570s and the Visigoths conquered much of Spain. The Byzantines also fought against the Sassanids, their long-lasting foes, in several indecisive wars.
In the 7th century, the Byzantine Empire began to decline. Already weakened by several schisms with the western church and plagued with political corruption, civil wars, and intrigues, the Byzantine Empire fared even worse in 632 when the Rashidun Caliphate was founded in Arabia. The Arabs conquered the Syria-Palestine region by 638 and Egypt by 641, and they even destroyed the mighty Sassanids, creating a large Muslim empire. The Byzantines fought against the Muslims, who converted most of the Christians in the Middle East to Islam and replaced churches with mosques. The 636 Battle of Yarmuk and the 655 Battle of the Masts were two shattering defeats, as Byzantine emperors had lost their whole armies (or fleets, in the latter case) to the Arabs. Later, the Arab dynasties were replaced by Turks, former slave soldiers of the Arabs who now fought to carve out their own Muslim Turkic dynasties in the Middle East. The Turks won the Battle of Manzikert in 1072 and took over most of Asia Minor from the Byzantines.
Another threat to Byzantium in the Dark Ages was the rise of the Holy Roman Empire. In 800, Charlemagne was crowned "Emperor of the Romans" by Pope Leo III, while Byzantine emperors were called "Emperor of the Greeks" by popes. This insulted the Byzantines, who sought to be recognized as successors to the Roman Empire of old. The Catholic German emperors and the Orthodox Greek emperors would have fierce rivalries, and when the Byzantine Empire begged for the help of the "Franks" (Western Europeans) in the First Crusade of 1096-1099, the Franks pillaged Byzantine cities and reneged on their promises to return all conquered lands to the Byzantines. The Byzantine Empire had a complex relationship with the crusader states of the Levant, sometimes allying with them but sometimes fighting them. In 1204, the crusaders sacked Constantinople after capturing it the previous year as a favor to a deposed Byzantine emperor. This "Fourth Crusade" never reached the Holy Land, as it diverted to Constantinople. After this, the Byzantine Empire was divided into the Latin Empire, Empire of Trebizond, Despotate of Epirus, Kingdom of Achaia, Kingdom of Thessalonica, and other Frankish states. In 1260, Michael Palaiologos conquered these states and took on the title "Michael VII of Byzantium", restoring the Byzantines to power in Constantinople.
However, the Byzantine Empire never regained its full strength. The Byzantines were confined to northwestern Turkey and Thrace, having lost most of their other lands. Even their islands of Rhodes and Cyprus had been lost to crusaders, so they ruled over a very small amount of territory. Byzantine emperors did not possess as much power as their ancestors did, and in 1299 Turkic warlord Osman founded the Ottoman Empire, which would take over much of Asia Minor. Only the Timurids' invasion of Turkey in 1402 halted the Ottoman advance against the Byzantines, but in 1453 the Ottomans besieged Constantinople. This time, Constantinople finally fell to the Muslims after several failed sieges of the cities by various foes. With the capture of Constantinople, the Roman Empire was no more.
- Constantine the Great (324-327) House of Flavii
- Constantius II (337-361) House of Flavii
- Julian the Apostate (361-363) House of Flavii
- Jovian (363-364) House of Flavii
- Valens (363-378) House of Flavii
- Vibius Flavius (364) House of Flavii/Eastern Roman Rebels
- Constans Pupienus (364) Eastern Roman Rebels
- Olybrius Canuleius (367) Eastern roman Rebels
- Theodosius I (379-401) House of Flavii
- Luca the Builder (401-406) House of Flavii
- Jovinus the Philosopher (406-429) House of Ofella
- Nepotianus Catulus (429) Eastern Roman Rebels
- Marcellus the Liar (429-463) House of Septimii
- Glycerius Arrianus (449) Eastern Roman Rebels
- Gainus Sittius (451) Eastern Roman Rebels
- Augustus Pacuvius (461-462) Eastern Roman Rebels
- Orestes (463-467) House of Stilicho
- Augustulus the Philosopher (467-481) House of Tacitii
- Gaius Timesitheus (470) Eastern Roman Rebels
- Ustus the Builder (481-489) House of Aetii
- Ustus II of Byzantium (489-) House of Fannii