Editing Middle Ages (section)

=== Byzantine survival ===
{{Main|Byzantine Empire under the Justinian dynasty|Byzantine Empire under the Heraclian dynasty}}

[[File:Sanvitale03.jpg|A [[mosaic]] showing [[Justinian]] with [[Maximianus of Ravenna|the bishop]] of [[Ravenna]] (Italy), bodyguards, and courtiers.<ref name=Adams158>Adams ''History of Western Art'' pp. 158–159</ref>|thumb|right]]

As Western Europe witnessed the formation of new kingdoms, the Eastern Roman Empire remained intact and experienced an economic revival that lasted into the early 7th century. There were fewer invasions of the eastern section of the empire; most occurred in the Balkans. Peace with the [[Sasanian Empire]], Rome's traditional enemy, lasted most of the 5th century. The Eastern Empire was marked by closer relations between the political state and the Christian Church, with doctrinal matters assuming an importance in Eastern politics that they did not have in Western Europe. Legal developments included the codification of [[Roman law]]; the first effort—the ''[[Codex Theodosianus]]''—was completed in 438.<ref name=Wickham81>Wickham ''Inheritance of Rome'' pp. 81–83</ref> Under Emperor Justinian (r. 527–565), another compilation took place—the ''[[Corpus Juris Civilis]]''.<ref name=Bauer200>Bauer ''History of the Medieval World'' pp. 200–202</ref> Justinian also oversaw the construction of the [[Hagia Sophia]] in Constantinople and the reconquest of North Africa from the Vandals and Italy from the Ostrogoths,<ref name=Bauer206 /> under [[Belisarius]] (d. 565).<ref name=Collins126>Collins ''Early Medieval Europe'' pp. 126, 130</ref> The conquest of Italy was not complete, as a deadly outbreak of [[Plague of Justinian|plague in 542]] led to the rest of Justinian's reign concentrating on defensive measures rather than further conquests.<ref name=Bauer206>Bauer ''History of the Medieval World'' pp. 206–213</ref>

At the Emperor's death, the Byzantines had control of [[Exarchate of Ravenna|most of Italy]], North Africa, and a small foothold in southern Spain. Historians have criticised Justinian's reconquests for overextending his realm and setting the stage for the [[early Muslim conquests]], but many of the difficulties faced by Justinian's successors were due not just to over-taxation to pay for his wars but to the essentially civilian nature of the empire, which made raising troops difficult.<ref name=Brown8>Brown "Transformation of the Roman Mediterranean" ''Oxford Illustrated History of Medieval Europe'' pp. 8–9</ref>

In the Eastern Empire, the Slavs' slow infiltration of the Balkans added further difficulty for Justinian's successors. It began gradually, but by the late 540s, Slavic tribes were in [[Thrace]] and [[Illyricum (Roman province)|Illyrium]] and had defeated an imperial army near [[Edirne|Adrianople]] in 551. In the 560s, the [[Pannonian Avars|Avars]] began to expand from their base on the north bank of the [[Danube]]; by the end of the 6th century, they were the dominant power in Central Europe and routinely able to force the Eastern emperors to pay tribute. They remained a strong power until 796.<ref name=James95>James ''Europe's Barbarians'' pp. 95–99</ref>

An additional problem to face the empire came as a result of the involvement of Emperor [[Maurice (emperor)|Maurice]] (r. 582–602) in Persian politics when he intervened in a [[Khosrow II#Accession to the throne|succession dispute]]. This led to a period of peace, but when Maurice was overthrown, [[Byzantine–Sasanian War of 602–628|the Persians invaded]] and during the reign of Emperor [[Heraclius]] (r. 610–641) controlled large chunks of the empire, including Egypt, Syria, and [[Anatolia]] until Heraclius' successful counterattack. In 628, the empire secured a peace treaty and recovered its lost territories.<ref name=Collins140>Collins ''Early Medieval Europe'' pp. 140–143</ref>