The Byzantine Empire, sometimes referred to as the Eastern Roman Empire, was the Greek-speaking continuation of the Roman Empire in the East during Late Antiquity and the Middle Ages, when its capital city was Constantinople (modern-day Istanbul, originally founded as Byzantium). It survived the fragmentation and fall of the Western Roman Empire in the 5th century AD and continued to exist for an additional thousand years until it fell to the Ottoman Turks in 1453.〔(Byzantine Empire. Britannica )〕 During most of its existence, the empire was the most powerful economic, cultural, and military force in Europe. Both "Byzantine Empire" and "Eastern Roman Empire" are historiographical terms created after the end of the realm; its citizens continued to refer to their empire as the ''Roman Empire'' (, tr. ; (ラテン語:Imperium Romanum)), or ''Romania'' (), and to themselves as "Romans".
Several events from the 4th to 6th centuries mark the period of transition during which the Roman Empire's Greek East and Latin West divided. 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 Byzantium from ancient Rome insofar as it was oriented towards Greek rather than Latin culture, and characterised by Orthodox Christianity rather than Roman polytheism.
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 the Byzantine–Sasanian War of 602–628, which exhausted the Empire's resources and contributed to major territorial losses during the Muslim conquests of the seventh century. In a matter of years the Empire lost its richest provinces, Egypt and Syria, to the Arabs.
During the Macedonian dynasty (10th–11th centuries), the Empire again expanded and experienced the two-century long Macedonian Renaissance, which came to an end with the loss of much of Asia Minor to the Seljuk Turks after the Battle of Manzikert in 1071. This battle opened the way for the Turks to settle in Anatolia as a homeland.
The final centuries of the Empire exhibited a general trend of decline. By the 12th century〔Rosenberg, Matt. "Largest cities through history." About.com.〕 Constantinople was the largest and wealthiest European city.〔Pounds, Norman John Greville. ''An Historical Geography of Europe, 1500–1840'', p. 124. CUP Archive, 1979. ISBN 0-521-22379-2.〕 The Empire struggled to recover during the 12th century, but was delivered a mortal blow during the Fourth Crusade, when Constantinople was sacked in 1204 and the territories that the Empire formerly governed were divided into competing Byzantine Greek and Latin realms. Despite the eventual recovery of Constantinople in 1261, the Byzantine Empire remained only one of several small rival states in the area for the final two centuries of its existence. Its remaining territories were progressively annexed by the Ottomans over the 15th century. The Fall of Constantinople to the Ottoman Empire in 1453 finally ended the Byzantine Empire.〔http://www.shsu.edu/~his_ncp/EndByz.html〕
== Nomenclature ==
The first use of the term "Byzantine" to label the later years of the Roman Empire was in 1557, when the German historian Hieronymus Wolf published his work ''Corpus Historiæ Byzantinæ'', a collection of historical sources. The term comes from "Byzantium", the name of the city of Constantinople before it became Constantine's capital. This older name of the city would rarely be used from this point onward except in historical or poetic contexts. The publication in 1648 of the ''Byzantine du Louvre'' (''Corpus Scriptorum Historiae Byzantinae''), and in 1680 of Du Cange's ''Historia Byzantina'' further popularised the use of "Byzantine" among French authors, such as Montesquieu.〔Fox, (What, If Anything, Is a Byzantine? ); 〕 However, it was not until the mid-19th century that the term came into general use in the Western world.〔.〕
The Byzantine Empire was known to its inhabitants as the "Roman Empire", the "Empire of the Romans" (Latin: ''Imperium Romanum'', ''Imperium Romanorum''; Greek: ''Basileia tōn Rhōmaiōn'', ''Archē tōn Rhōmaiōn''), "Romania" (Latin: ''Romania''; Greek: ''Rhōmania''), the "Roman Republic" (Latin: ''Res Publica Romana''; Greek: ''Politeia tōn Rhōmaiōn''), ''Graikia'' (Greek: Γραικία), and also as ''Rhōmais'' (Greek: ).〔; Theodore the Studite, ''Epistulae'', 145, line 19 ("ἡ ταπεινὴ Γραικία"), and 458, line 28 ("ἐν Ἀρμενίᾳ καὶ Γραικίᾳ").〕 The inhabitants called themselves ''Romaioi'' and ''Graikoi'', and even as late as the 19th century Greeks typically referred to their modern language as ''Romaika'' and ''Graikika''.
Although the Byzantine Empire had a multi-ethnic character during most of its history〔; .〕 and preserved Romano-Hellenistic traditions,〔.〕 it became identified by its western and northern contemporaries with its increasingly predominant Greek element.〔; ; ; ; ; ; ; .〕 The occasional use of the term "Empire of the Greeks" (Latin: ''Imperium Graecorum'') in the West to refer to the Eastern Roman Empire and of the Byzantine Emperor as ''Imperator Graecorum'' (Emperor of the Greeks)〔; ''Annales Fuldenses'', 389: "Mense lanuario c. epiphaniam Basilii, Graecorum imperatoris, legati cum muneribus et epistolis ad Hludowicum regem Radasbonam venerunt ...".〕 were also used to separate it from the prestige of the Roman Empire within the new kingdoms of the West.〔: "The Frankish court no longer regarded the Byzantine Empire as holding valid claims of universality; instead it was now termed the 'Empire of the Greeks'."〕
The authority of the Byzantine emperor as the legitimate Roman emperor was challenged by the coronation of Charlemagne as ''Imperator Augustus'' by Pope Leo III in the year 800. Needing Charlemagne's support in his struggle against his enemies in Rome, Leo used the lack of a male occupant of the throne of the Roman Empire at the time to claim that it was vacant and that he could therefore crown a new Emperor himself.〔.〕 Whenever the Popes or the rulers of the West made use of the name ''Roman'' to refer to the Eastern Roman Emperors, they usually preferred the term ''Imperator Romaniae'' (meaning ''Emperor of Romania'') instead of ''Imperator Romanorum'' (meaning ''Emperor of the Romans''), a title that they applied only to Charlemagne and his successors.
No such distinction existed in the Islamic and Slavic worlds, where the Empire was more straightforwardly seen as the continuation of the Roman Empire. In the Islamic world, the Roman Empire was known primarily as ''Rûm''.〔; 〕 The name millet-i Rûm, or "''Roman nation,''" was used by the Ottomans through the 20th century to refer to the former subjects of the Byzantine Empire, that is, the Orthodox Christian community within Ottoman realms.
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