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Thehistory of the Later Roman Empire covers thehistory of the Roman Empire from the beginning of the rule ofDiocletian in 284AD (1037AVC) and the establishment of theTetrarchy in 293 AD by Diocletian to the death ofHeraclius in 641 AD (1394 AVC).^{[citation needed]}

The Roman Empire underwent acritical period of crisis after EmperorSeverus Alexander was murdered in 235 AD. During the following fifty years, twenty emperors ruled, and most of them were assassinated by their own troops. In case of emergency, local officials and military commanders took full control of state administration in large regions. Examples include theGallic Empire along theLimes Germanicus, and QueenZenobia'sPalmyrene Empire in Syria.^[1][2] In the east, the PersianSasanians who replaced theParthian Arsacids adopted an offensive policy against Rome. With the emergence of theSasanian Empire, Rome ceased to be the sole great power in the Near East. In the west, larger tribal confederation took the place of smallGermanic tribes. Among the new tribal federation, theFranks lived along the Lower Rhine, theAlemanni on the Upper Rhine, and theGoths near theLower Danube. The Roman Empire survived the crisis with minimal territorial losses: onlyDacia to the north of the Lower Danube, and theAgri Decumates in theBlack Forest region were abandoned in the 270s. Egypt and north Africa, the economically most valuable regions, were far away from the principal theatres of war, and remained almost unharmed.^[3]

The army quickly grew in size and the soldiers were no more kept away from the central territories in the 3rd century. The continued payment of soldiery could be secured only by the regulardebasement of the Roman silver coins, thedenarii. As soon as the population realized that the face value of thedenarii in circulation was much higher than their silver content, inflation became uncontrollable. Old coins that contained silver or gold were quickly withdrawn from circulation and treasured. The unmanageable inflation increased the significance of taxation in kind. Regular demands for theannona militaris—the compulsory grain supply to the army—and theangareia—the mandatory military transport—put an enormous strain on the population of the highly militarized regions. The eastern cities, likeAntioch and Athens, could quickly recover invasions by enemy forces, but the towns in the less prosperous western provinces were declining.^[4]

The Christians' reluctance to make sacrifices was unacceptable for most Romans. Classical authors likeTacitus andPliny the Younger describe the Christians as opponents of traditional Roman values. Although the Christians were outlawed, they were only sporadically persecuted, and mainly fanatical extremists, especially the PhrygianMontanists were sentenced to death. Significant Christian communities existed in the largest urban centers, like Rome, Antioch,Alexandria andCarthage, and their size quickly grew in the first half of the 3rd century. Convinced that religious laxity threatened national security, EmperorDecius ordered that all citizens were to sacrifice to the gods in 249. During theensuing persecution, great numbers of non-compliant Christians were executed or forced into exile. Deciusdied fighting the Goths in 251, but five years laterValerian resumed the persecution which lasted until he was captured by Sassanian troops in theBattle of Edessa in 260.^[5] EmperorCarus embarked on a new invasion of the Sassanian Empire, but a bolt of lightning struck him to death in the Persian capital,Ctesiphon in July 283. His younger sonNumerian abandoned the campaign, but he died while wintering in the eastern provinces.^[6]

On learning of the death of Carus and Numerian, senior officers staying inNicomedia proclaimed one of their number, theIllyrianDiocletian, emperor on 20 November 284. Diocletian marched to Illyricum to fight Carus' elder son,Carinus, but Carinus was assassinated by one of his own retainers in theBattle of the Margus.^[7] Diocletian, who had no son, made a Pannonian officerMaximian his co-ruler, first asCaesar in 285, then as juniorAugustus in 286. The power-sharing agreement proved durable, with Diocletian mostly ruling in the East, and Maximian in the West. Thediarchy developed into atetrarchy—the rule of four co-emperors—when Diocletian appointed two officers from Illyricum,Constantius Chlorus andGalerius, as Caesars in 293. The relationship between the four emperors was reinforced through marriage alliances: Galerius married Diocletian's daughterGaleria Valeria, and Constantius wed Maximian's daughterTheodora.^[8][9]

Secessionist movements continued. A mutinous military commanderCarausius held sway overBritain and northernGaul from 286 until Constantius overcame him in 293.Domitius Domitianus ruledEgypt until Diocletian capturedAlexandria in 297.^[10] The tetrarchs launched military campaigns along the borderlands and restored its strategic control. Galerius forced the Persian king,Narseh to cede lands along the riverTigris to Rome and reimposed Roman suzerainty over theKingdom of Iberia. Diocletian and Galerius waged wars against the Goths,Carpi,Sarmatians,Quadi andMarcomanni along the Danube. Maximian and Constantius defeated the Franks on the Rhine. Maximian went on war against theQuinquegentiani ("Five Peoples") inMauretania.^[11] The four co-rulers' cooperation and military achievements created a period of stability, allowing the introduction of profound administrative and financial reforms. Examples include the reorganization of theprovinces and the development of a sophisticated tax system.^[12] Diocletian became convinced that the empire's integrity could only be reinforced through the renewal of the traditional religion and outlawed Christianity in 303.^[13] During the subsequent Great Persecution, many Christians suffered martyrdom.^[14]

The first tetrarchy ended with an unprecedented act, the voluntary retirement of Diocletian and Maximian on 1 May 305. On this occasion, Galerius and Constantius Chlorus were promoted to the rank of Augustus, and two Illyrian military commanders,Maximinus Daia andValerius Severus, were appointed as the new Caesars. Their appointment apparently demonstrates Galerius' influence on the ailing Diocletian: Maximinus Daia was his nephew and Valerius Severus was his friend. Although both Constantius' son,Constantine, and Maximian's son,Maxentius, were adults, the composition of the new tetrarchy ignored their claims to succeed their fathers. When Constantius Chlorus died in Britain on 25 July 306, his troops proclaimed Constantine his successor. Three months later, Maxentius took control of southern and central Italy and Africa. Valerius Severus attacked Maxentius, but his troops who had served under Maximian mutinied and captured him. After seizing northern Italy, Maxentius persuaded his father to abandon his retirement and again rule as Augustus in spring 307. Constantine married Maximian's daughterFausta, and his new father-in-law appointed him as Augustus. After a conflict between Maximian and Maxentius, Maximian sought refuge at Constantine, and the governor ofAfrica,Domitius Alexander assumed the imperial title.^[17]

To tackle the chaotic situation Galerius convinced Diocletian to preside over a conference atCarnuntum in November 308. The conference established a new tetrarchy, with Galerius and his Dacian protégé,Licinius asAugusti, and Maximinus Daia and Constantine asCaesares. Neither Maximinus nor Constantine acquiesced in their degradation, and both Maxentius and Domitius Alexander insisted on their imperial status. Maxentius sent an expeditionary force against Domitius Alexander and reconquered Africa, while Maximian staged a coup against Constantine. The coup failed and Maximian was forced to commit suicide in summer 310. After Galerius, the last surviving ruler of the first tetrarchy, died in May 311, Constantine made an alliance with Licinius against Maxentius and Maximinus Daia. Maxentius died fighting Constantine in theBattle of the Milvian Bridge on 28 October 312, and Licinius routed Maximinus Daiain Thrace on 30 April 313.^[18][19]

Licinius had not yet won his war against Maximinus Daia when he married Constantine's half-sisterConstantia in Milan in February 313. The two emperors jointly issued a law about religious tolerance, now known as theEdict of Milan. No more excluded from imperial service, Christians could have brilliant careers, likeAblabius, a Greek of humble origin, who held the highest offices between 324 and 331.^[20][21] Relationship between the two emperors grew tense and Constantine seized theDioceses of Pannonia andMoesia by force in 318. Six years later Constantine launched a new attack against Licinius and forced him to abdicate. In a year, Licinius and his about ten-year-old son by Constantia, also calledLicinius, were executed.^[22] The tragic child had been appointed as Caesar along with Constantine's two eldest sons,Crispus andConstantine II in 317. Crispus' motherMinervina was Constantine's first wife, while the younger Constantine was born to Fausta. In 326, Crispus and Fausta were executed on mysterious charges, likely because of their adulterous relationship.^[23][24] Always hostile to the first Christian emperor, Zosimus alludes that Constantine's actual conversion to Christianity was the consequence of their execution, because only Christianity offered himabsolution for his sin. Constantine made his younger sons by Fausta,Constantius II andConstans, and his nephewDalmatius Caesars, and appointed Dalmatius' brotherHannibalianus ruler of thePontic regions.^[25][26]

Constantine continued Diocletian's administrative and financial reforms, butChristian ethics had an impact on his legislation. He banned gladiator games and promoted the less violentchariot racing. He forbade thebranding of slaves on the forehead, abolished penalties forcelibacy, and offered financial support to poor parents to discourage infanticide. On the other hand, he prescribed that a slave nurse participating in a girl's abduction be punished with molten lead poured down her throat, and a woman who abandoned her husband was to be banished pennilessly to a remote island.^[27][28] Constantine established a new city at a highly defensible place on the site of the ancient Greekpolis ofByzantium on theBosporus in 324. In four years, his "New Rome" was surrounded by walls enclosing about 600 hectares (1,500 acres) of land, and it was adorned with all elements of an imperial capital, including a palace and a large stadium. The city was consecrated asConstantinople on 11 May 330.^[29] Constantine launchedsuccessful campaigns against the Goths in 332 and 336, and against the Sarmatians in 334. The new Persian kingShapur II invaded Armenia and expelled the Roman client kingTigran VII. Constantine decided to launch a counter-attack, but he died unexpectedly on 22 May 337.^[30] His stepbrothers and their sons were soon massacred likely on Constantius II's initiative. Only two childrenGallus andJulian survived the purge.^[23]

Constantine II, Constantius II, and Constans met in Pannonia in September 337. They assumed the title of Augustus and divided the empire, with Constantine ruling the western, Constans the central and Constantius the eastern regions. Constantius restored Roman protectorate over Armenia and secured the Roman control of the eastern borderlands through a series of military campaigns against Persia.^[31][32] In 340, Constantine attacked Constans reportedly to avenge a slight, but died fighting atAquileia. Constans seized his territory, but he could not gain the support of the army. A military commander of Germanic origin,Magnentius staged a coup against him in Gaul, and Constans was murdered by his own troops in early 350. In Illyricum, an other high-ranking officerVetranio assumed the imperial title allegedly with the support of Constans' sisterConstantina. Constantius could deal with the usurpers after defeating the Persians atNisibis. He forced Vetranio to surrender and married off Constantina to their cousin, Gallus, whom he made Caesar with responsibility for the eastern borderland. Constantius inflicted three major defeats on Magnentius who committed suicide in 352. Gallus proved himself incompetent to rule: he crushed aJewish revolt with excessive cruelty and ordered the execution of citizens on false charges. He was imprisoned and executed on Constantius' order in 354. Constantius made Gallus' younger half-brother Julian Caesar charging him with the command of Gaul and returned to Mesopotamia to repel a Persian invasion. He ordered Julian to send Gallic troops to the east, but they rioted and proclaimed Julian Augustus. Constantius departed for the west to fight Julian, but he died unexpectedly inCilicia in November 361. To avoid a civil war, Constantius' troops acknowledged Julian as his sole successor.^[33][34]

Julian had received a Christian education, but he was captivated byNeoplatonic mysticism in his youth. During the reign of Constantius II, he had to conceal his pagan sympathies, but as emperor he could openly adhere to paganism. He declared the restoration of religious tolerance as his principal object, but he prohibited Christians from teaching rhetoric and grammar. He wanted to justify his conversion to paganism by a splendid victory, buthis invasion of Persia failed. While his army was retreating from Mesopotamia, he was killed in a skirmish on 26 June 363.^[35][36] After a high-ranking pagan officialSalutius refused the imperial title, a Christian military commander,Jovian was proclaimed emperor. He abandonedRoman territories in Mesopotamia and acknowledged Persian protectorate over Armenia in return for a thirty-year peace treaty with Shapur II. He died unexpectedly in February 364.^[37]

The commanders of Jovian's army discussed his succession with civil officials at Nicaea. On 26 February 364, they elected a Pannonian tribuneValentinian I emperor, and about a month later, Valentinian appointed his younger brotherValens his co-ruler. They divided the empire with Valentinian ruling in the West, and Valens in the East.^[38] After a severe illness, Valentinian made his sonGratian the third co-emperor. AlthoughPicts,Scoti,Attacotti, Alemanni,Saxons,Quadi, Sarmatians and Goths launched regular raids across the imperial borders, the Roman army pacified the situation. In the east, Valens had to face a rebellion by Julian's relativeProcopius, but he quickly crushed itin Lydia in 366.^[39] After launching two invasions across the Lower Danube, Valens forced the Goths to renounce their claim to a yearly contribution from Rome.^[40] When Valentinian I died in November 375, leaders of his army proclaimed his four-year-old sonValentinian II emperor. Gratian acknowledged his half-brother's promotion, but in practice he ruled the western part of the empire alone.^[41]

From the 350s, the nomadicHuns were invading thePontic steppes from the east, and the natives could not long resist them. In the summer of 376, thousands of Goths fleeing from the Huns gathered along the northern bank of the Lower Danube to seek asylum in the Roman Empire.^[42] Regarding them as potential recruits, Valens allowed them to settle inThrace, but failure to provide ample amounts of food, and abuses by Roman officials outraged the Goths. Further waves of asylum seekers crossed the river and the Goths rose up in rebellion. Valens had concentrated his troops in Antioch in preparation for a military campaign against Persia, and the Roman troops left behind in the Balkans could not crush the rebellion. Valens sought military assistance from Gratian, while the Goths hired Huns andAlans to invade Roman territory. Without waiting for the arrival of reinforcements from the west, Valens engaged the Goths in personat Adrianople on 9 August 378. TheEast Roman army was nearly annihilated and Valens died in the battlefield.^[43][44] Gratian appointed a talented generalTheodosius to deal with deteriorating situations in the Balkans, and awarded him with the title Augustus early in 379. Theodosius recruited new troops, but he was unable to defeat the rebels. The conflict ended with a compromise in 382, unprecedented and humiliating to the Romans: the Goths were allowed to settle in groups in Thrace and Pannonia asfoederati, or allies, but they were not subjected to Roman officials' rule.^[45] Theodosius appointed his elder sonArcadius co-emperor.^[46]

Gratian's alleged favoritism towards his Alan mercenaries outraged the Roman troops in Britain and they proclaimed their commanderMagnus Maximus emperor in 383. Gratian was assassinated by his own guards in August, and Maximus took control of the western provinces to the north of theAlps. He invaded Italy and forced the young Valentinian II and his family to seek refuge in Thessaloniki in 387. After marrying Valentinian II's sisterGalla, Theodosius launched a surprise attack against Maximus. Unable to resist, Maximus was captured and executed at Aquileia. In 388, Valentinian returned to the West, but Theodosius appointed a Frankish military commanderArbogast as the young emperor's guardian.^[47] In the east, Theodosius and the Sassanian kingShapur IIIdivided Armenia to avoid a new war. Western Armenia was incorporated into the Roman Empire, but the new provinces were ruled by localArmenian hereditary governors.^[48] Arbogast openly disobeyed Valentinian's orders and the young emperor committed suicide in 392. With Arbogast's support, a Roman pagan aristocrat,Eugenius was proclaimed emperor. Theodosius elevated his younger sonHonorius to the status of Augustus before departing for a military campaign against Eugenius. He inflicted a decisive defeat on the usurper in theBattle of the Frigidus on 6 September 394. He re-unified the Roman Empire, but he died on 17 January 395.^[49]

Theodosius I was succeeded by the eighteen-year-old Arcadius in the East, and the ten-year-old Honorius in the West. The notion of imperial unity persisted, although divergences between the two realms deepened.^[51] A Western Roman general of half-Vandal originStilicho announced that the dying Theodosius had appointed him the guardian of both emperors, but his claim to rule theEastern Roman Empire was challenged by thepraetorian prefectRufinus.^[52][53] Taking advantage of their conflict,Alaric I the leader of a group of Goths who became known asVisigoths established a new power centre in the Balkans.^[54] Attacking the empire from the east, the Huns pillaged Syria and Cappadocia. Rufinus' opponents blamed him for the calamities and a Gothic commander in Roman service,Gainas murdered him in November 395. During the ensuing power struggle, theeunuchEutropius assumed power with Arcadius' consent.^[55] In 397, Stilicho invadedAchaea allegedly to attack Alaric, but Eutropius was worried about Stilicho's ambitions. On his advice, Arcadius declared Stilicho a public enemy, forcing him to return to the west. Eutropius was unpopular and the Gothic troops' riot inPhrygia provided an excuse for Gainas to achieve his deposition in 399. Gainas took control of state administration, but an anti-Gothic riot in Constantinople enabled Arcadius to remove him with the support of an other Gothic generalFravitta.^[56]

The empire faced new waves of mass migrations likely triggered by the Huns' westward expansion. Around 405, a mixed group of peoples invaded Italy under the command of a Gothic chieftainRadagaisus, but Stilicho overcame themat Florence. On 31 December 406, tens of thousands of Vandals, Alans,Suebi, Sarmatians and "hostile Pannonians"crossed the Rhine into Gaul.^[57][58] Insecurity led to insurrections in Britain, and the rebellious troops proclaimed their commanders emperors, but only one of them,Constantine III could consolidate his position. He crossed the Channel and restored peace along the Rhine through treaties with the Franks, Alemanni andBurgundians. The western crisis compromised Stilicho's position.^[59][60]

When Arcadius died on 1 May 408, his seven-year-old sonTheodosius II succeeded him under the tutelage of the praetorian prefectAnthemius. A Hunnic leader,Uldin invaded the Balkans and demanded a tribute, but Anthemius forced him to abandon the campaign by bribing his lieutenants.^[61][62] Taking advantage of the Romans' distrust of Stilicho's foreign mercenaries, his former protégéOlympius staged a coup and achieved Stilicho's execution.^[63] Searching for a new homeland, the Vandals and their allies left Gaul and invaded theIberian Peninsula in 409. Constantine III appointed his sonConstans to take command of the defence, but the generalGerotnius disobeyed and proclaimed oneMaximus emperor inTarraco.^[64] Alaric invaded Italy in the autumn of 408. He demanded tribute and his appointment to a senior military office, but his negotiations with Honorius failed. On his demand, the Senatus proclaimed a Roman aristocratPriscus Attalus emperor, but Honorius resisted at Ravenna with the support of Eastern Roman reinforcements. Alaric attacked Rome and the Visigothssacked the city on 24 August 410. As historianPeter Heather emphasizes, the Visigoths carried out "one of the most civilized sacks of a city ever witnessed", but their capture of the old capital shocked the Roman world. After abandoning Rome, Alaric decided to conquer the wealthy northern African provinces, but a storm destroyed his fleet and he died in southern Italy.^[65][66]

As Honorius could no more guarantee the defense of Britain, he suggested the provincials to provide for their own protection in 410. The influx of Roman coins stopped, indicating that Britainceased to be an integral part of the Roman world.^[67] The Vandals and their allies took control of most Roman provinces in Iberia, and Alaric's successor,Athaulf led the Visigoths to Gaul from Italy.^[68] Maximus attacked Constantine III in Gaul, but his troops deserted him on the unexpected arrival of Honorius' army under the command of the generalConstantius. Maximus fled, and Constantine III was executed, but Western Roman unity was not restored. With the support of the Burgundians, Alans and Visigoths, a Gallic aristocratJovinus was declared emperor on the Rhine. His alliance with the Visigoths proved transitory because Honorius convinced Athaulf to desert Jovinus promising food supply to his people. Although Athaulf murdered Jovian, the Romans failed to deliver the promised grain. Athaulf married Honorius' half-sisterGalla Placidia who had been captured during the sack of Rome, but fell victim to a Visigothic conspiracy in 415. Constantius restored Roman rule in southern and central Iberia and cededAquitania Secunda to the Visigoths in return for their assistance against the Vandals, Alans and Suebi.^[69][70]

Constantius married the widowed Galla Placidia and the childless Honorius appointed them Augustus andAugusta early in 421, but Theodosius II did not acknowledge Constantius' promotion. Constantius died while planning a military campaign against the Eastern Roman Empire, and Galla Placidia lost Honorius' favor. She fled to Constantinople along with her children,Valentinian andHonoria shortly before Honorius died on 15 August 423. Three months later a high-ranking official,John was elected emperor in Rome, but Theodosius proclaimed the six-year-old Valentinian Caesar. In preparation for an invasion from the Eastern Roman Empire, John ordered thecura palatii ("curator of the palace")Flavius Aetius to hire Hunnic mercenary troops. Aetius who had spent years with the Huns as a hostage succeeded, but by the time he returned to Italy, an Eastern Roman expeditionary force had defeated John's army. John was executed and Valentinian was acknowledged as the new emperor in the west. Aetius persuaded his Hunnic mercenaries to leave Italy in return for his appointment as the new military commander in Gaul. As Valentinian was still a minor, high-ranking officers like Aetius and the military commander of AfricaBonifatius were competing for power.^[71][72]

The Vandals and Alans suffered heavy losses during their fights with the Romans and Visigoths in Iberia and their kingGaiseric decided to guide them to northern Africa in 429. They landed atTangiers and Bonifatius was unable to stop their advance. The Eastern Roman generalAspar came to the rescue ofCarthage, but Bonifatius was ordered to return to Italy, probably by Galla Placidia who needed his support against Aetius. Bonifacius routed Aetiusat Rimini, but he died of the wounds received in the battle. Aetius secured the Huns' support, enforcing his appointment as thesupreme commander of the Western Roman army in 433. In two years the Eastern Roman reinforcements left Carthage and Valentinian concluded a peace treaty with the Vandals, acknowledging their acquisition of much of northern Africa. The Huns had meanwhile established their new power base in the plains along the riverTisza and Valentinian had to cede Pannonia to them.^[73][74]

The Huns extracted 350 pounds of gold as a yearly tribute from the Eastern Roman Empire, and the amount was doubled in a new treaty in 434. The same treaty prohibited the Romans to receive fugitives from theHunnic Empire, but the influx of asylum seekers could not be stopped.^[75] The Vandals resumed the war andcaptured Carthage in 439.^[76] Theodosius dispatched relief troops to north Africa, but a Hunnic invasion of the northern Balkans forced him to abandon the naval campaign.^[77] In return for the renewal of the peace treaty, Theodosius agreed to pay a higher yearly tribute, probably 1,400 pounds of gold, but after his fleet returned from northern Africa he ceased to pay it.^[78] In 442 Valentinian acknowledged the Vandals' conquest of two wealthy provinces, Africa proconsularis andByzacena in return for their abandonment of the rest of theMaghreb. The Vandals built a new fleet and emerged as a major naval power in the western Mediterranean.^[76] To enforce the tribute payment from the Eastern Romans, the Hunnic king Attila plundered the Balkans as far as Constantinople andThermopylae in 447. He only withdrew his troops when Theodosius agreed to pay 6,000 pounds of gold in compensation for the arrears and increase the annual tribute to 2,100 pounds of gold.^[78]

The childless Theodosius died in a riding accident on 28 July 450. His sisterPulcheria chose an elderly military commanderMarcian as her husband without consulting with Valentinian. She allegedly acted in concern with the all-powerful Aspar who had been Marcian's superior in the army. Marcian was proclaimed emperor in Constantinople in late August. On learning of Attila's plan about a military campaign in the west he stopped tribute payments to the Huns.^{[note 3][79][80]} Attila launched a massive incursion into Gaul at the head of a mixed army of Huns and subject peoples. Aetius assembled Roman, Visigothic and Burgundian troops and engaged the enemyat the Catalaunian fields in June 451. Although the battle was inconclusive, Attila withdrew from Gaul. Next year he invaded Italy, but supply problems and an epidemic forced him to again withdraw. He died unexpectedly of bleeding in 453. In a year, the Hunnic Empire collapsed due to a civil war between his sons and a revolt of the subject peoples. With the Hunnic threat vanishing, Valentinian got rid of the domineering Aetius with the assistance of his eunuch courtierHeraclius who murder the general in September 454. Aetius' death was revenged by his two retainers who assassinated Valentinian on 16 March 455.^[81][82]

Officials who were staying at Rome proclaimed one of their numberPetronius Maximus as Valentinian's successor. He married Valentinian's widowLicinia Eudoxia. Her elder daughter by ValentinianEudocia was married off to Maximus' sonPalladius breaking her engagement to Gaiseric's heir,Huneric.^[83][84] The Vandals occupied the remnants of Roman Africa and Geiseric sent his fleet against Rome. News of the arrival of the Vandal ships caused panic in the city and a mob slaughtered Maximus and Palladius on 31 May. The Vandalssacked Rome for two weeks and captured many prisoners, among them Licinia Eudoxia and her two daughters, Eudocia andPlacidia. While Rome was in anarchy, the Gallic troops proclaimed their commanderAvitus emperor. He hastened to Rome, but his attempts to secure his Gallic and Visigothic soldiers' food supply and salary at all costs caused a general discontent. In October 456, two powerful generalsRicimer andMajorian took up arms against him, enforcing his abdication. The two generals entered into negotiations with Marcian about Avitus' succession, but Marcian died in Constantinople on 26 January 457. Marcian's son-in-lawAnthemius was bypassed, and the still powerful Aspar secured the Eastern Roman throne for theThracianLeo I who had been his lieutenant. Leo rewarded Ricimer and Majorian with honors and the two generals agreed that Majorian was to rule the Western Empire first as Caesar, then as Augustus. Majorian restored imperial rule in Gaul and launched successful campaigns against the Visigoths and Suebi, but his position weakened after the Vandalscrushed his fleet.^[85][86]

Assuming the role of king-maker, Ricimer captured and executed Majoran and proclaimedLibius Severus, a man of unknown background, emperor in 461. Leo and most Western Roman generals did not acknowledge Severus' ascension. The Western Roman Empire quickly disintegrated asAegidius held sway over Gaul andMarcellinus assumed power in Dalmatia. The Vandals seizedCorsica,Sardinia and theBalearic Island. Severus died in November 465. A sixteen-month-long interregnum followed until Ricimer and Leo accepted Anthemius as a compromise candidate. Marcellinus accompanied Anthemius to Rome and Ricimer married Anthemius' daughterAlypia. Eastern and western forces were united for a common attack against the Vandals in Sardinia and Sicily, but during the campaign Marcellinus was murdered, likely on Ricimer's order. In Gaul, the imperial government left the provincials to their fate.^[87] After Aegidius died in 464, his sonSyagrius ruled the Roman enclaves.^[88] In the east, Leo I promoted the career of an Isaurian commanderZeno to diminish Aspar's power. He married off his daughterAriadne to Zeno, but his younger daughterLeontia was in short married to Aspar's sonPatricius who was made Caesar on this occasion. In 471 a popular riot broke out against Aspar and his mainly Gothic troops in Constantinople, enabling Leo to arrest and murder Aspar. The Gothic mercenaries mutinied and the rebellion enabled the Pannonian Goths, known asOstrogoths, to invade the Balkans, and theGepids to seizeSirmium. Leo could only appease the Ostrogoths through land grants in Macedonia and Thrace.^[89]

Relationship between Ricimer and Anthemius grew tense and Ricimer attacked Rome with the assistance with his Burgundian nephewGundobad. Leo appointed a Roman aristocratOlybrius to mediate between Anthemius and Ricimer. Olybrius had married Valentinian III's younger daughter Placidia. On his arrival to Rome, he was proclaimed emperor by Ricimer. In July 472Rome surrendered and Ricimer's troops killed Anthemius, but both Ricimer and Olybrius died before the end of the year. After a five-month interregnum, Gundobad acclaimedGlycerius, a court official, emperor, but Leo sent Marcellinus' nephewJulius Nepos to Rome to claim the imperial throne. Gundobad's father, the Burgundian kingGondioc, died in 473, and he left Italy to claim his inheritance. After his protector's departure, Glycerius abdicated in Julius Nepos' favor.^[90] In Constantinople, Leo was succeeded by his seven-year-old grandsonLeo II in 474. His father Zeno assumed the regency. When the child-emperor died before the end of the year Zeno became the new emperor. His mother-in-lawVerina and her brotherBasiliscus forced him to flee from Constantinople with the support of the Isaurian generalIllus and the Ostrogothic leaderTheoderic Strabo. Basiliscus was proclaimed emperor, but he lost popular support due to his interventions in church affairs. Zeno returned to Constantinople and deposed Basiliscus without much opposition in 476.^[91] In Rome, a powerful Pannonian generalOrestes mutinied against Julius Nepos, forcing him to withdraw to Dalmatia. Orestes proclaimed his sonRomulus Augustulus the new emperor at Ravenna, but he was unable to pay off his troops and they rebelled. One of their commanders,Odoacer, captured Orestes anddeposed Romulus Augustulus on 4 September 476.^[92][93]

The early-6th-century historianMarcellinus Comes states that the "Western Empire of the Roman people perished" with the deposition of Romulus Augustulus. Odoacer's appointment as patricius by Zeno legitimized his position as the actual ruler of Italy, but he mainly styled himselfrex ("king") in official documents. He recognized Julius Nepos and Zeno as emperors and minted coins in their name. The Visigothic kingEuriccaptured Arles andMarseille in Gaul. After Zeno confirmed his conquest, Euric began the systematic conquest of the Iberian Peninsula. In 480 Julius Nepos was assassinated and Odoacer seized Dalmatia.^[95][96] Syagrius died fighting the Franksat Soissons and their kingClovis I conquered thelast Roman enclave in Gaul in 486.^[88] Zeno had been unable to stabilise his rule in the east. Unpaid Ostrogothic troops launched pillaging raids against the Balkan provinces and Theodoric Strabo nearly captured Constantinople before died in a riding accident in 481. Zeno's claim to rule was challenged by his brother-in-lawMarcianus in 479, and by the Isaurian generalLeontius in 484, but he overcame them with the support of hastily mustered troops. To eliminate Ostrogothic threat from the Balkans, he offered Odoacer's realm to the Ostrogothic kingTheodoric the Amal, who completed the conquest of Dalmatia and Italy between 488 and 493. He had Odoacer executed.^[97][98]

As Zeno outlived his two sons, his death caused a succession crisis in April 491. His brotherLonginus could claim the throne, but the high-ranking officials despised him. On their intervention the widowed Ariadne chose an elderly court official,Anastasius I Dicorus, as her second husband and the new emperor. He exiled Longinus to Egypt, and his troopscrushed a revolt by Longinus' supporters in Isauria. Popular riots and street-fighting between the fans of two racing teams, theGreens and theBlues, caused much destruction in Constantinople. The Lower Danube remained barely defended, enabling Hunnic,Bulgar andSlavic groups to make frequent pillaging raids against the Balkan provinces.^[99] In the east, Arabs raided Syria and Palestine, and the Sassanian kingKavad I demanded a tribute from Anastasius in 502. Anastasius refused, but after years ofmutual invasions, promised to pay a symbolic yearly tribute of 36,900nomismata.^[100] He died on 8 July 518. Two days later, the Senate elected the Latin-speaking commander of thepalace guardJustin I emperor. He summoned his relatives to the imperial court and appointed Illyrians to high offices.^[101][102] In Italy, Theoderic discovered that Roman senators entered into correspondence about the restoration of Roman rule and had them arrested for treason in 523. Hismagister officiorum, or master of offices,Boethius were among the suspects, and Theoderic had him executed. The Christian kings of the CaucasianLazica and Iberia sought Justin's protection against the Sassanians. In retaliation, Kavad Iresumed the war against the Romans.^[103]

The childless and ailing Justin appointed his nephewJustinian I as Augustus shortly before he died on 1 August 527.^[104] Justinian was one of the most ambitious Roman emperors and he implemented systematic reforms to improve state administration and the army. He continued the war against the Sassanians, but neither the Roman nor the Persian army could achieve a decisive victory. In spring of 532 Justinian and the new Sassanian kingKhosrow I concluded apeace treaty whereby Justinian paid 11,000 pounds of gold, reportedly in remuneration for the defense of the Caucasian passes by the Sassanians.^[105] Justinian introduced harsh measures against rioters to restore public order in the major cities, and his officials implemented his laws with great vigour. After a bloody riot following the races on 10 January 532, seven fans of the racing teams were arrested for murder. Five were executed, but one each from the Blue and the Green team escaped. Three days later, at the next racing, the Blues and the Greens made public appeals to Justinian on the two convicts' behalf, but he ignored them. The fans of both clubs united in a riot of elementary force, chanting the word Nika ("Conquer!") as a rallying cry. Although theNika riots lasted for less than a week, the rioters destroyed much of the city center. Justinian's three generals,Narses,Belisarius andMundus, crushed the riot mercilessly, reportedly slaughtering at least 30,000 townspeople.^[106]

The pro-Roman Vandal kingHilderic was deposed by his cousinGelimer in 530. The ensuing insurrections in Sardinia andTripolitania provided Justinian with a pretext to intervene. He appointed Belisarius to lead theinvasion against theVandal Kingdom early in 533. Theodoric's daughter,Amalasuntha, who ruled theOstrogothic Kingdom in Italy as regent for her sonAthalaric, allowed the Roman expeditionary forces to use the port of Syracuse during the campaign. In a year, Belisarius defeated the Vandals with thenative population's support and conquered their kingdom. The pacification of the reconquered northern African territories lasted for years because of riots by unruly Berber tribes and their cooperations with rebellious Roman troops. In Italy, Athalaric died and Amalasuntha's cousinTheodahad had her assassinated in 535.^[107][108] An unidentified natural catastrophe, likely dust from a major volcanic eruption,darkened the sun between 24 March 535 and 24 June 536. The low temperature caused disastrous crop failures and massive famine.^[109] The catastrophe did not prevent Justinian from going towar against the Ostrogoths. In 535 Mundus conquered Dalmatia and Belisarius captured Sicily. During the following five years, Belisarius occupied almost whole Italy, but an Ostrogothic kingdom survived in the north.^[110] Taking advantage of the concentration of the Roman troops in Italy, the Bulgars launched a pillaging raid over the Balkans, and Khosrow resumed the war. He invaded Syria, sacked Antioch and restored Sassanian suzerainty over Lazica.^[111]

From 541 to 543, the first outbreak ofbubonic plague ravaged the Roman Empire and its neighbors. The death toll was tremendous, particularly in the largest cities,^{[note 4]} and epidemic recurred several times. Justinian was among the few who caught the plague but survived.^[112][113] Although the Sassanian Empire was also struck by the plague, Khosrow made a new incursion against Syria in 544. His siege ofEdessa was unsuccessful, and early next year he signed a five-year truce in return for the lump sum of 144,000nomismata.^[114] The conflict between the two empires enabled the Ostrogothic king,Totila to expel the Romans from much of Italy. Cooperating with unpaid Roman troops, he could termporarily seize Romein 546 and550. Justinian sent Narses with fresh troops to Italy and he defeated the Ostrogothsat Taginae in 552. Totila perished in the battlefield, and his successorTeia died fighting in theBattle of Mons Lactarius. The Ostrogothic Kingdom collapsed, although small Ostrogothic groups resisted atCumae and other places till 562.^[115] In 551, a rebellious Visigothic aristocrat,Athanagild, sought Roman alliance against KingAgila. Justinian appointed the praetorian prefect of ItalyLiberius to lead an expeditionary force against the Visigothic Kingdom. Cooperating with Roman rebels, Liberius conquered southern Hispania.^[116] To defend the Balkan provinces against further raids by the HunnicUtigurs, the Romans persuaded an other steppe people theKutrigurs to attack them in the 550s. The Kutrigurs were attacked from the east by the nomadicAvars. Tensions along the western frontier developed into a new armed conflict between Rome and the Sassanians until anew peace treaty was signed for fifty years in 562.^[117]

Justinian, as historianWarren Treadgold emphasizes, "had added more land to the empire than any emperors but Trajan and Augustus",^[118] but the preservation of the territorialstatus quo was a costly enterprise. When Justinian died on 14 November 565, the sole courtier who was present, thesacellarius Callinicus stated that the dying emperor had named his nephewJustin II as his sole heir. Justinian's death was announced only after Justin's coronation.^[119] The Avars defeated the Gepids and conquered their realm in alliance with theLombards in 567. After the Gepids' fall, the Romans seized Sirmium, and the Lombard kingAlboin realized that he could not resist an Avar invasion of Pannonia.^[120] He led his people to Italy where they occupied thePo Valley. After Alboin was murdered in 573, ambitious Lombard chieftains continued the conquest, but central Italy,Naples,Calabria and Sicily remained under Roman rule. In southern Iberia, the Visigothic kingLiuvigild capturedMálaga,Medina-Sidonia andCórdova from the Romans. A Berber kingGarmul targeted northern Africa and inflicted major defeats on the Romans.^[121][122] After an Armenian revolt, Justinresumed the war against Persia, but the Persians quickly halted the Roman invasion and Khosrow I capturedDara on 15 November 573. On learning of the fall of this key fortress of Roman defense, Justin experienced a nervous breakdown. His wifeSophia and the senators jointly convinced him to appoint his friend the Thracian generalTiberius Caesar in late 574.^[123]

Tiberius paid 45,000 solidi to Khosrow for a one-year peace. A year later he agreed to pay a yearly tribute of 30,000 solidi. He was proclaimed Augustus shortly before Justin died on 26 September 578.^[124] He wanted to renew the peace treaty with the Persians, but the new Sassanian kingHormizd IV refused, likely because he was aware of the Romans' troubles in the West. Tiberius appointed a Cappadocian generalMaurice the commander of the eastern army. The unpaid troops were on the verge of mutiny, but Maurice adopted an offensive tactic until a Persian counter-invasion forced him into retreat. Unable to wage war on two fronts simultaneously, Tiberius left the Balkan frontiers undefended.^[125] He hired the Avars to prevent Slavic raids over the Lower Danube, but he failed to pay the promised yearly tribute—about 1,100 pounds of gold—to them. In retaliation, the Avarsseized Sirmium in 582. From then on, the Slavs freely crossed the Lower Danube and started to settle in Roman territory.^[126]

On his deathbed, Tiberius – who had no sons – proclaimed Maurice Augustus. When Tiberius died in August or October 582, Maurice succeeded as the sole emperor. He was the first emperor to speak Greek at native level since Anastasius. He married Tiberius' daughterConstantina.^[127][128] He hired the Frankish kingChildebert II to attack the Lombards, and with Frankish assistance the Romans halted the Lombard expansion in Italy. The Avars and Slavs made devastating raids as far as Marcianopolis and Thessaloniki, but both towns resisted their attack. In 590, a rebellious Persian general,Bahram Chobin, murdered Hormizd IV and forced his heirKhosrow II to seek asylum with the Romans. Khosrow approached Maurice for assistance and Maurice appointed the generalNarses to invade the Sassanian Empire. The Romans and Khosrow's supporters routed Bahram in theBattle of the Blarathon. After regaining his throne, Khosrow ceded Armenia and eastern Mesopotamia, including Dara, to the Romans. The peace allowed Maurice to relocate his troops to the Balkans and they launched aseries of invasions against Slavic and Avar territory after 593.^[129] When a famine caused a riot in Constantinople in 602, Maurice ordered a Roman army to winter in Slavic territory, living off the land over the Danube, but the troops mutinied and proclaimed thecenturionPhocas emperor. Phocas led his partisans to Constantinople, and a riot forced Maurice to flee the city. After Phocas secured the support of the Greens and theSenate, PatriarchCyriacus II of Constantinople crowned him emperor on 23 November. Four days later, Maurice and his sons were captured and executed.^[130][131]

Phocas replaced many high-ranking officers with his relatives. He could not gain popularity, and he faced popular riots in Constanstinople. The Avars and the Lombards made simultaneous raids against Dalmatia, and Slavic troops in Avar service assisted the Lombards to captureCremona andMantua in Italy. In the east, Narses took up arms in favor of a young pretender whom he had identified as Maurice's son,Theodosius, claiming that Theodosius survived the purge. A hastily concluded peace treaty with the Avars enabled Phocas to deploy troops against Narses from the Balkans. As the Balkans was left almost undefended, the Slavs resumed their raids and attacked Thessaloniki. Narses's revolt provided Khosrow II with a pretext to capture and destroy Dara in 604. Narses was fooled into surrender with a promise of amnesty, but Phocas had him burnt alive.^[132][133]

The plague returned and a bad harvest caused a famine in 608. Maurice's old comradeHeraclius, who was the governor of Roman Africa,revolted and refused to ship grain to Constantinople. He sent a fleet to Sicily under the command of his son and namesake, and appointed his nephewNicetas to invade Egypt. Phocas was forced to relocate troops from the eastern provinces to Egypt, enabling the Persians to make raids as far as the Bosporus. In 610, Nicetas overcame the loyalist forces in Egypt, and the youngerHeraclius sailed for Constantinople. On his arrival in October, the Greens and the commander of the imperial guard,Priscus deserted to him. A mob captured Phocas and dragged him to Heraclius, who reportedly beheaded him in person.^[134][135]

On Heraclius' ascension the empire was in ruins. His father died in Africa, and he could trust only a few people. He concentrated his troops in Anatolia and appointed Priscus as their commander. Between 610 and 613, the Persians capturedCaesarea in Cappadocia, and Antioch,Apamea andEmesa in Syria. Heraclius dismissed Priscus and took command of the Anatolian army in person, but the Persians routed him near Antioch. The Sassanian generalShahrbaraz seized Damascus and Jerusalem. After he left Jerusalem the Christians expelled his garrison, but he quickly returned andconquered the city. He deported the mass of the Christian population to Persia. Meanwhile, Slavic tribes seized much of Illyricum, the Avars capturedSalona,Naissus andSerdica, and the Visigoths conquered most Roman territory in Iberia.^[136][137]

The Persian invasion continued: Shahrbaraz occupied Egypt in 620, and an other Persian general,Shahin launched devastating raids against Anatolia. Heraclius could muster new troops only after he convinced PatriarchSergius I of Constantinople to lend gold and silver to the state. In early 622 he made a truce with the Avars and attacked the Persians in Anatolia. He defeated Shahrbaraz in Cilicia, but news of an Avar invasion of Thrace forced him to return to Constantinople. He paid 200,000 nomismata to the Avars for the renewal of the truce, and hastened back to the eastern theatre of war. The Persians and Avars joined their forces in anattack on Constantinople in the summer of 626, but they could not conquer the city. The Slavs revolted against their Avar overlords and the Avars could not again attack the Romans. Heraclius resumed the invasion of the Sassanian Empire and routed the Persiansat Nineveh. Khosrow was murdered and his sonKavad II concluded a peace treaty with Heraclius, giving up all territories that his predecessors had conquered from the Romans after 591. The Sassanian Empire plunged into anarchy and Roman rule was quickly restored in Syria and Egypt.^[138][139]

The Romans did not regard the disorganized Arab tribes of theArabian Desert as potentially dangerous enemies early in the 7th century.^[140] However, the ArabicGhassanids andLakhmids had been deeply involved in the Roman–Persian wars, and the Arabization of the Near East had started. Arab tribes settled in thinly populated lands near the Roman–Persian frontier, and the thriving Syrian and Mesopotamian cities attracted Arab settlers. The situation changed rapidly with the unification of the desert tribes by theIslamic prophet Muhammad between 622 and 632. After he died, his monotheistic movement was led by his successors, styledcaliphs, who were both the political and religious leaders of the Islamic community. Conducting thejihad, or Islamic holy war, against the "infidels", the Arabs attacked the Syrian Roman territories and conquered Damascus in 633.^[141] Heraclius deployed a Roman field army against the Arabs, but they annihilated the Roman armyon the Yarmuk River in Syria in 636. As the war against Persia had exhausted the empire, Heraclius could not send a second field army against the invaders and they conquered Syria. Two years later, the Arabs inflicted a major defeat on the Persiansat Qadisiyyah.^[142] As the Arabs continued the invasion, Heraclius sent reinforcements to Egypt, but they could not halt the invaders. PatriarchCyrus of Alexandria offered a yearly tribute of 200,000 nomismata to the Arab generalAmr ibn al-As for a truce and went to Constantinople to seek imperial confirmation. Heraclius refused, likely because he knew that a tribute would not stop the conquerors on the long run.^[143] On Cyrus' arrival, Heraclius was already dying, and he died on 11 February 641.^[144]

The ancient world came to an abrupt end withearly Islamic conquests.^[145] The Sassanian Empire collapsed and the Arabs completedits conquest by 651. The Roman Empire persisted, but its territory shrunk.^[146] With the loss of Syria, Egypt and Africa, Rome was no more the dominant Mediterranean power, and the Roman state persisted in the east mainly in the shadow of the more powerfulUmayyad Caliphate.^[9] The empire's remaining citizens continued to regard themselves as Romans (Greek: Ρωμαίοι), however since 610 the official language was changed to Greek. The term "Byzantines", nowadays applied in reference to them, is an early modern scholarly invention.^[147]

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