The date of 476 was popularized by the 18th-century British historian Edward Gibbon as a demarcating event for the fall of the Western Roman Empire and is sometimes used to mark the transition from Antiquity to the Middle Ages.
Political instability in the Eastern heartlands, combined with foreign invasions, plague, and religious differences, made efforts to retain control of these territories difficult and they were gradually lost for good.
[4] Prior to the establishment of the Empire, the territories of the Roman Republic had been divided in 43 BC among the members of the Second Triumvirate: Mark Antony, Octavian and Marcus Aemilius Lepidus.
The Praetorian Guard, a figurative "sword of Damocles", was often perceived as being of dubious loyalty, primarily due its role in court intrigues and in overthrowing several emperors, including Pertinax and Aurelian.
During this period, the Empire saw the combined pressures of barbarian invasions and migrations into Roman territory, civil wars, peasant rebellions and political instability, with multiple usurpers competing for power.
[22] Saloninus, Gallienus' infant son, and the praetorian prefect Silvanus resided in Colonia Agrippina (modern Cologne) to solidify the loyalty of the local legions.
Mistreatment caused a full-scale rebellion, and in 378 they inflicted a crippling defeat on the Eastern Roman field army in the Battle of Adrianople, in which Emperor Valens also died.
As the imperial government was not providing the military protection the northern provinces expected and needed, numerous usurpers arose in Britain, including Marcus (406–407), Gratian (407), and Constantine III who invaded Gaul in 407.
The weakening of the Rhine frontier allowed multiple barbarian tribes, including the Vandals, Alans and Suebi, to cross the river and enter Roman territory in 406.
With Constantius back in Italy, the Gallo-Roman senator Jovinus revolted after proclaiming himself emperor, with the support of the Gallic nobility and the barbarian Burgundians and Alans.
[64] With the Roman legions withdrawn, northern Gaul became increasingly subject to Frankish influence, the Franks naturally adopting a leading role in the region.
Honorius' death in 423 was followed by turmoil until the Eastern Roman government installed Valentinian III as Western emperor in Ravenna by force of arms, with Galla Placidia acting as regent during her son's minority.
Aetius transferred his forces to the Danube,[68] though Attila concentrated on raiding the Eastern Roman provinces in the Balkans, providing temporary relief to the Western Empire.
In 449, Attila received a message from Honoria, Valentinian III's sister, offering him half the western empire if he would rescue her from an unwanted marriage that her brother was forcing her into.
At the Battle of Arelate, Majorian decisively defeated the Visigoths under Theoderic II and forced them to relinquish their great conquests in Hispania and return to foederati status.
Unable to take the throne for himself due to his barbarian heritage, Ricimer appointed a series of puppet emperors who could do little to halt the collapse of Roman authority and the loss of the territories re-conquered by Majorian.
[79] Severus died in 465 and Leo I, with the consent of Ricimer, appointed the capable Eastern general Anthemius as Western emperor following an eighteen-month interregnum.
[83] By convention, the Western Roman Empire is deemed to have ended on 4 September 476, when Odoacer deposed Romulus Augustus, but the historical record calls this determination into question.
[84] Syagrius, who had managed to preserve Roman sovereignty in an exclave in northern Gaul (a realm today known as the Domain of Soissons) also recognized Nepos as his sovereign and the legitimate Western emperor.
[93] The Germanic kingdoms in Italy, Hispania and Gaul continued to recognise the emperor in Constantinople as a somewhat nominal sovereign, the Visigoths minted coins in their names until the reign of Justinian I in the sixth century.
An inscription on a fortification at the ruined city of Altava from the year 508 identifies a man named Masuna as the king of "Regnum Maurorum et Romanarum", the Kingdom of the Moors and Romans.
[95] Amalasuntha continued the policies of conciliation between the Goths and Romans, supporting the new Eastern emperor Justinian I and allowing him to use Sicily as a staging point during the reconquest of Africa in the Vandalic War.
The end of the conflict saw Italy devastated and considerably depopulated, which, combined with the disastrous effects of the Plague of Justinian, made it difficult to retain over the following centuries.
After 600, events conspired to drive the Western provinces out of Constantinople's control, with imperial attention focused on the pressing issues of war with Sasanian Persia and then the rise of Islam.
Thereafter, imperial attention declined, with Constantinople itself being besieged in the 670s, renewed war with the Arabs in the 680s, and then a period of chaos between 695 and 717, during which time Africa was finally lost once and for all, being conquered by the Umayyad Caliphate.
[72] As Rome was invaded by Germanic tribes, many assimilated, and by the middle of the medieval period (c. 9th and 10th centuries) the central, western, and northern parts of Europe had been largely converted to Roman Catholicism and acknowledged the Pope as the Vicar of Christ.
Its authority increased under the rule of Odoacer and later the Ostrogoths, evident by the Senate in 498 managing to install Symmachus as pope despite both Theodoric of Italy and Emperor Anastasius supporting another candidate, Laurentius.
[146] At the end of Emperor Tiberius II's reign in 582, the Eastern Roman Empire retained control over relatively large parts of the regions reconquered under Justinian.
Pope Leo III and contemporary historians were fully aware that the notion of a separate Western court had been abolished over three centuries prior and considered the Roman Empire to be "one and indivisible".
In 423, after the death of Honorius, a usurper named Joannes rose up, forcing Valentinian III to flee with his family to the court of the Eastern emperor Theodosius II.