As a matter of historical convention, the late Roman Empire emerged from the
Principate (the early Roman Empire), with the accession of Diocletian in 284, following the
Third Century Crisis of AD 235–284. or of
Heraclius (AD 641). The subsequent period of centuries of the Roman Empire's history is conventionally labelled the "
Byzantine Empire", with the reign of Heraclius beginning the Middle Byzantine period, which lasted until the
Fourth Crusade.
284–301: Diocletian and the Tetrarchy sculpture sacked from a
Byzantine palace in 1204, Treasury of
St Mark's,
Venice The transition to divided western and eastern halves of the empire was gradual. In July 285, Diocletian defeated rival emperor
Carinus and briefly became sole emperor of the Roman Empire. Diocletian's reign stabilised the empire and marked the end of the Crisis of the Third Century. Diocletian appointed a co-emperor in 286 and delegated further with two junior-emperors. Diocletian secured the empire's borders and purged it of all threats to his power. He defeated the
Sarmatians and
Carpi during several campaigns between 285 and 299, the Alamanni in 288, and usurpers in
Egypt between 297 and 298. Galerius, aided by Diocletian, campaigned successfully against
Sassanid Persia, the empire's traditional enemy. In 299, he sacked their capital, Ctesiphon. Diocletian led the subsequent negotiations and achieved a lasting and favourable peace. Diocletian separated and enlarged the empire's civil and military services and reorganised the empire's provincial divisions, establishing the largest and most
bureaucratic government in the history of the empire. He established new administrative centres in
Nicomedia,
Mediolanum, Antioch, and
Trier, closer to the empire's frontiers than the traditional capital at Rome had been. Building on third-century trends towards
absolutism, he styled himself an autocrat, elevating himself above the empire's masses with imposing forms of court ceremonies and architecture. Bureaucratic and military growth, constant campaigning, and construction projects increased the state's expenditures and necessitated a comprehensive tax reform. From at least 297 on, imperial taxation was standardised, made more equitable, and levied at generally higher rates. Diocletian saw that the vast Roman Empire was ungovernable by a single emperor in the face of internal pressures and military threats on two fronts. He therefore split the Empire in half along a northwest axis just east of Italy, and created two equal emperors to rule under the title of
augustus. Diocletian himself was the
augustus of the eastern half, and he made his long-time friend
Maximian augustus of the western half. In doing so, he effectively created what would become the western empire and the eastern empire. On 1 March 293, authority was further divided. Each
augustus took a junior emperor called a
caesar to aid him in administrative matters, and to provide a line of succession.
Galerius became
caesar for Diocletian and
Constantius Chlorus caesar for Maximian. This constituted what is called the Tetrarchy by modern scholars, as each emperor would rule over a quarter-division of the empire. After the empire had been plagued by bloody disputes about the supreme authority, this finally formalised a peaceful succession of the emperor: in each half a
caesar would rise up to replace the
augustus and select a new
caesar. On 1 May 305, Diocletian and Maximian abdicated in favour of their
caesares. Galerius named the two new
caesares: his nephew
Maximinus Daia for himself, and
Valerius Severus for Constantius. The arrangement worked well under Diocletian and Maximian and shortly thereafter. The internal tensions within the Roman government were less acute than they had been. In
The History of the Decline and Fall of the Roman Empire,
Edward Gibbon notes that this arrangement worked well because of the affinity the four rulers had for each other. Gibbon says that this arrangement has been compared to a "chorus of music". With the retirement of Diocletian and Maximian, this harmony disappeared. After an initial period of tolerance, Diocletian, who was a fervent pagan and was worried about the ever-increasing numbers of Christians in the Empire,
persecuted them with zeal unknown since the time of Nero; this was to be one of the greatest persecutions the Christians endured in history. Not all of Diocletian's plans were successful: the
Edict on Maximum Prices (301), his attempt to curb
inflation via
price controls, was counterproductive and quickly ignored. Although effective while he ruled, Diocletian's tetrarchic system collapsed after his abdication under the competing dynastic claims of
Maxentius and Constantine, sons of Maximian and Constantius respectively. The
Diocletianic Persecution (303–11), the empire's last, largest, and bloodiest official persecution of
Christianity, did not destroy the empire's Christian community; indeed, after 324 Christianity became the empire's preferred religion under its first Christian emperor, Constantine. '' struck in
Antioch under
Constantius Chlorus, the
tetrarchs are sacrificing to celebrate a victory against the
Sarmatians. In spite of his failures, Diocletian's reforms fundamentally changed the structure of Roman imperial government and helped stabilise the empire economically and militarily, enabling the empire to remain essentially intact for another hundred years despite being near the brink of collapse in Diocletian's youth. Weakened by illness, Diocletian left the imperial office on 1 May 305, and became the first Roman emperor to voluntarily abdicate the position (
John VI retired to a monastery in the 14th century). He lived out his retirement in
his palace on the Dalmatian coast, tending to his vegetable gardens. His palace eventually became the core of the modern-day city of
Split. The peaceful Tetrarchy would effectively collapse with the death of Constantius Chlorus on 25 July 306. Constantius's troops in
Eboracum immediately proclaimed his son
Constantine the Great as
augustus. In August 306, Galerius promoted Severus to the position of
augustus. A revolt in Rome supported another claimant to the same title: Maxentius, son of Maximian, who was proclaimed
augustus on 28 October 306. His election was supported by the Praetorian Guard and the Roman Senate. This left the Empire with five rulers: four
augusti (Galerius, Constantine, Severus and Maxentius) and one
caesar (Maximinus). The year 307 saw the return of Maximian to the rank of
augustus alongside his son Maxentius, creating a total of six rulers of the Empire. Galerius and Severus campaigned against them in Italy. Severus was killed under command of Maxentius on 16 September 307. The two
augusti of Italy also managed to ally themselves with Constantine by having Constantine marry
Fausta, the daughter of Maximian and sister of Maxentius. At the end of 307, the Empire had four
augusti (Maximian, Galerius, Constantine and Maxentius) and a sole
caesar. In 311, Galerius's
Edict of Serdica officially put an end to the persecution of Christians, though the persecution continued in the territory of Maximinius Daia until his death in 313. Constantine and his co-
augustus Licinius legalised Christianity definitively in 313 in the so-called
Edict of Milan. In 317, Constantine and Licinius elevated three of the grandchildren of Constantius to
caesar: Constantine's eldest sons
Crispus and
Constantine II, and his nephew, Licinius's son
Licinius II. Constantine defeated his brother-in-law in 324 and executed both him and his son. This unified the empire under his control as sole
augustus, with only his young sons as co-emperors; he raised his son
Constantius II to
caesar in 324.
324–363: Constantinian dynasty Constantine and his sons : from west to east, the territories of
Constantine II,
Constans,
Dalmatius and
Constantius II Having executed his eldest son and
caesar Crispus in 326, Constantine also elevated his son
Constans to
caesar in 333, as well as appointing his relatives
Dalmatius and
Hannibalianus to
caesar and
King of Kings respectively. Constantine would rule until his death on 22 May 337. On their father's death, an interregnum followed during which Constantine II, Constantius II, and Constans eliminated most of the Constantinian dynasty in a struggle for power that ended with the elevation of the three brothers as co-
augusti in September 337. The empire was parted again among his three surviving sons. Constantine II was killed in conflict with his youngest brother in 340. Constans was himself killed in conflict with the rebel
augustus Magnentius on 18 January 350. Magnentius was at first opposed in the city of Rome by self-proclaimed
augustus Nepotianus, a paternal first cousin of Constans. Nepotianus was killed alongside his mother
Eutropia. His other first cousin Constantia convinced
Vetranio to proclaim himself
caesar in opposition to Magnentius. Vetranio served a brief term from 1 March to 25 December 350. He was then forced to abdicate by the legitimate
augustus Constantius. The
usurper Magnentius would continue to rule the western Roman Empire until 353 while in conflict with Constantius. His eventual defeat and suicide left Constantius as sole emperor until the nomination of his cousin
Constantius Gallus as his
caesar and co-emperor. Constantius's rule would, however, be opposed again in 360. After his execution of Constantius Gallus, the
augustus Constantius had named his paternal half-cousin and brother-in-law
Julian as his
caesar in 355, sending him to rule from Trier. During the following five years, Julian had a series of victories against invading
Germanic tribes, including the
Alamanni. This allowed him to secure the Rhine frontier. His victorious
Gallic troops thus ceased campaigning. Constantius sent orders for the troops to be transferred to the east as reinforcements for his own currently unsuccessful campaign against
Shapur II of Persia. This order led the Gallic troops to an
insurrection. They
acclaimed, invested, and crowned their commanding officer Julian as
augustus after the decisive
Battle of Strasbourg, a distinction he had previously been offered but declined. Both
augusti readied their troops for another Roman civil war, but the timely demise of Constantius on 3 November 361 and his deathbed recognition of Julian as co-
augustus prevented the
Roman civil war of 350–353 from reaching Constantinople.
361–363: Julian Julian would serve as the sole emperor for two years. He had been raised by the
Gothic slave
Mardonius, a great admirer of
ancient Greek philosophy and
literature. Julian had received his
baptism as a
Christian years before, but no longer considered himself one. His reign would see the ending of restrictions and violence against paganism introduced by his uncle and father-in-law Constantine I and his cousins and brothers-in-law Constantine II, Constans and Constantius II. He instead placed similar restrictions on Christianity, and some unofficial violence against Christians occurred. His
edict of toleration in 362 ordered the reopening of pagan
temples and the reinstitution of alienated temple properties, and, more problematically for the
Christian Church, the recalling of previously exiled Christian
bishops. Returning orthodox and
Arian bishops resumed their conflicts, thus further weakening the Church as a whole. Julian himself was not a traditional pagan. His personal beliefs were largely influenced by
Neoplatonism and
Theurgy; he reputedly believed he was the
reincarnation of
Alexander the Great. He produced works of
philosophy arguing his beliefs. His brief renaissance of paganism would, however, end with his death. Julian eventually resumed the war against
Shapur II of Persia. He received a mortal wound in battle and died on 26 June 363. According to Gibbon in
The Decline and Fall of the Roman Empire, upon being mortally wounded by a dart, he was carried back to his camp. He gave a farewell speech, in which he refused to name a successor. He then proceeded to debate the philosophical nature of the soul with his generals. He then requested water and, shortly after drinking it, died. He was considered a hero by pagan sources of his time and a villain by Christian ones. Gibbon wrote quite favourably about Julian. Contemporary historians have treated him as a controversial figure.
364: Jovian Julian died childless and with no designated successor. The officers of his army elected the rather obscure officer
Jovian emperor. He is remembered for signing an unfavourable
peace treaty with the
Sasanian Empire, ceding territories won from the Persians, dating back to
Trajan. He restored the privileges of Christianity. He is considered a Christian himself, though little is known of his beliefs. Jovian himself died on 17 February 364.
364–392: Valentinianic dynasty Valentinian and Valens The role of choosing a new
augustus fell again to army officers. On 28 February 364,
Pannonian officer
Valentinian I was elected
augustus in
Nicaea,
Bithynia. The army had been left leaderless twice in less than a year, and the officers demanded Valentinian choose a co-ruler. On 28 March, Valentinian chose his own younger brother
Valens and the two new
augusti parted the empire in the pattern established by Diocletian: Valentinian would administer the western provinces, while Valens took control over the eastern empire. The election of Valens was soon disputed.
Procopius, a
Cilician maternal cousin of Julian, had been considered a likely heir to his cousin but was never designated as such. He had been in hiding since the election of Jovian. In 365, while Valentinian was at Paris and then at Rheims to direct the operations of his generals against the Alamanni, Procopius managed to
bribe two
legions assigned to Constantinople and take control of Constantinople. He was acclaimed
augustus on 28 September and soon extended his control to both
Thrace and Bithynia. War between the rival emperors continued until Procopius was defeated. Valens had him executed on 27 May 366. On 4 August 367, the eight-year-old
Gratian was proclaimed as a third
augustus by his father Valentinian, who had fallen ill, a nominal co-ruler and means to secure succession. In April 375, Valentinian I led his army in a campaign against the
Quadi, a
Germanic tribe which had invaded his native region of Pannonia. According to
Ammianus Marcellinus, during an audience with an
embassy from the Quadi at
Brigetio on the Danube, Valentinian suffered a burst blood vessel in his brain while angrily yelling at the people gathered, resulting in his death on 17 November 375. Gratian was then a 16-year-old and arguably ready to act as emperor, but the troops in Pannonia proclaimed his infant half-brother emperor under the title
Valentinian II. Valens and Gratian acquiesced in their choice. While the senior
augustus administered the eastern empire, Gratian governed the
praetorian prefecture of Gaul. The
praetorian prefecture of Italy, Illyricum, and Africa were officially administrated by infant brother and Gratian's stepmother
Justina. However the division was merely nominal, actual authority in the west still rested with Gratian, and with Valens as the senior emperor.
Battle of Adrianople (378) invasions of the Roman Empire, showing the Battle of Adrianople Meanwhile, the Eastern Roman Empire faced its own problems with Germanic tribes. The
Thervingi, an
East Germanic tribe, fled their former lands following an invasion by the
Huns. Their leaders
Alavivus and
Fritigern led them to seek refuge in the Eastern Roman Empire. Valens allowed them to settle as
foederati on the southern bank of the Danube in 376. However, the newcomers faced problems from allegedly
corrupted provincial commanders and a series of hardships. Their dissatisfaction led them to revolt against their Roman hosts. Conflicts continued for the following two years. Valens led a campaign against them in 378. Gratian provided his uncle with reinforcements from the western Roman army. However, this campaign proved disastrous for the Romans. The two armies approached each other near
Adrianople. Valens was apparently overconfident of the numerical superiority of his own forces over the Goths. Some of his officers advised caution and to await the arrival of Gratian, others urged an immediate attack and eventually prevailed over Valens, who, eager to have all of the glory for himself, rushed into battle. On 9 August 378, the
Battle of Adrianople resulted in the crushing defeat of the Romans and the death of Valens. Contemporary historian
Ammianus Marcellinus estimated that two-thirds of the Roman army were lost in the battle. The battle had far-reaching consequences. Veteran soldiers and valuable administrators were among the heavy casualties. There were few available replacements at the time, leaving the Empire with the problem of finding suitable leadership. The
Roman army also started to face recruiting problems. In the following century much of the Roman army would consist of Germanic mercenaries.
Gratian and Valentinian II The death of Valens left Gratian and Valentinian II as the sole
augusti. Gratian was now effectively responsible for the whole empire. He sought a replacement
augustus for the Eastern Roman Empire. His choice was
Theodosius I, son of formerly distinguished
magister equitum Count Theodosius. The elder Theodosius had been executed in early 375 for unclear reasons. The younger Theodosius was named Gratian and Valentinian's junior co-
augustus on 19 January 379, at Sirmium. Gratian governed the western Roman Empire with energy and success for some years, but he gradually sank into indolence. He is considered to have become a
figurehead while
Frankish general
Merobaudes and bishop
Ambrose of
Milan jointly acted as the
power behind the throne. Gratian lost favour with factions of the
Roman Senate by prohibiting traditional paganism at Rome and relinquishing his title of
Pontifex maximus. The senior
augustus also became unpopular with his own Roman troops because of his close association with so-called
barbarians. He reportedly recruited
Alans to his personal service and adopted the guise of a
Scythian
warrior for public appearances. Meanwhile, Gratian, Valentinian II and Theodosius were joined by a fourth
augustus. Theodosius elevated his oldest son
Arcadius to
augustus in January 383, in an obvious attempt to secure succession. The boy was still only five or six years old and held no actual authority. Nevertheless, he was recognised as a co-emperor by all three
augusti.
383–388: rebellion of Magnus Maximus The increasing unpopularity of Gratian would cause the four
augusti problems later that same year.
Magnus Maximus, a general from Hispania, stationed in
Roman Britain, was proclaimed
augustus by his troops in 383 and, rebelling against Gratian, he invaded Gaul. Gratian fled from
Lutetia (
Paris) to Lugdunum (
Lyon), where he was assassinated on 25 August 383, at the age of 25. Maximus was a firm believer of the
Nicene Creed and introduced state persecution on charges of
heresy, which brought him into conflict with
Pope Siricius, who argued that the
augustus had no authority over church matters. But he was an emperor with popular support, as is attested in
Romano-British tradition, where he gained a place in the
Mabinogion, compiled about a thousand years after his death. Following Gratian's death, Maximus had to deal with Valentinian II, at the time only twelve years old, as the senior
augustus. During the first few years, the
Alps would serve as the borders between the respective territories of the two rival western Roman emperors. Maximus controlled the
praetorian prefecture of Gaul. He assumed the government at Augusta Treverorum (
Trier), the prefecture's capital. Maximus soon entered negotiations with Valentinian II and Theodosius, attempting to gain their official recognition. By 384 negotiations were unfruitful and Maximus tried to press the matter by settling succession as only a legitimate emperor could do: proclaiming his own infant son
Flavius Victor an
augustus. The end of the year found the Empire having five
augusti (Valentinian II, Theodosius I, Arcadius, Magnus Maximus and Flavius Victor) with relations between them yet to be determined. Theodosius was left a widower in 385, following the sudden death of
Aelia Flaccilla, his
augusta and the mother of Arcadius and
Honorius. In 386, Maximus and Victor finally received official recognition by Theodosius but not by Valentinian. In 387, Maximus apparently decided to rid himself of his Italian rival. He crossed the Alps into the valley of the
Po and threatened Milan. Theodosius was remarried to the sister of Valentinian II, Galla, after their mother Justina fled with the young emperor to Theodosius's territory to escape Magnus Maximus's invasion of Italy. The marriage secured closer relations between the two
augusti. Theodosius indeed campaigned west in 388 and was victorious against Maximus. Maximus himself was captured and executed in
Aquileia on 28 July 388. The
magister militum Arbogast was sent to Trier with orders to also kill Flavius Victor. Theodosius restored Valentinian to power and through his influence had him converted to orthodox catholic Christianity. Theodosius continued supporting Valentinian and protecting him from a variety of usurpations.
379–457: Valentinianic–Theodosian dynasty s on the
Obelisk of Theodosius in
Istanbul (
Constantinople), showing Roman emperor
Theodosius I surrounded by members of his court and receiving
tributary gifts from foreign emissaries, late 4th century AD
392–394: rebellion of Eugenius In 392
Valentinian II died mysteriously in
Vienne. Arbogast, who may have killed him, arranged for the appointment of
Eugenius as emperor. However, the eastern emperor
Theodosius refused to recognise Eugenius as emperor and invaded the West, defeating and killing Arbogast and Eugenius at the
Battle of the Frigidus. He thus reunited the entire Roman Empire under his rule, the last emperor who had practical power over the whole empire. On his death in February 395, the two halves of the Empire went to his two sons
Arcadius and
Honorius.
395–423: Arcadius and Honorius Arcadius became ruler in the East, with his capital in Constantinople, and Honorius became ruler in the West, with his capital in Milan and later
Ravenna. The Roman state would continue to have two different emperors with different seats of power throughout the 5th century, though the eastern Romans considered themselves to be the only ones who were fully Roman. Latin was used in official writings as much as, if not more than, Greek and the two halves were nominally, culturally and historically, if not politically, the same state. Arcadius died in 408, having already elevated his infant son
Theodosius II to
augustus in 402. Theodosius II reigned for more than forty years. Theodosius had two sons and a daughter,
Pulcheria, from his first wife,
Aelia Flacilla. His daughter and wife had died in 385. By his second wife, Galla, the daughter of
Valentinian the Great, he had a daughter,
Galla Placidia; his son Gratian did not survive infancy. Galla Placidia, having grown up at Constantinople, married first
Athaulf, king of the Visigoths, and then the future
Constantius III. Both her husbands died not long after the marriages, and Constantius III, who succeeded Honorius as
augustus, reigned for less than a year. Galla Placidia and Constantius had two children: the future
Valentinian III, who became
augustus in the western empire, and
Justa Grata Honoria. On the death of Honorius, the official
Joannes seized power in Italy and Thedosius II appointed Valentinian III his
caesar and dispatched him to the western empire with an army, which deposed Joannes and whose commander elevated Valentinian to
augustus on the first anniversary of his appointment as
caesar. His mother the
augusta Galla Placidia was regent during his youth. Valentinian III married Theodosius II's daughter
Licinia Eudoxia and reigned for three decades until his murder by the rebel
augustus Petronius Maximus and his
caesar Palladius, who forced Valentinian's wife Licinia and daughter Placidia to marry them. On the death of Theodosius II, the military officer
Marcian was acclaimed Valentinian III's co-
augustus and married the late emperor's elder sister, the
augusta Pulcheria. Marcian was the last of the Theodosians to rule in the east, and only connected to them by marriage to the
augusta. When Pulcheria died in 453 and Marcian died in 457, ending the Theodosian line, the court at Constantinople selected the general
Leo I as his successor as
augustus, beginning the reign of the
Leonid dynasty.
Decline of the Western Roman Empire After 395, the emperors in the western empire were usually figureheads, while the actual rulers were military strongmen who took the title of
magister militum,
patrician or both—
Stilicho from 395 to 408,
Constantius from about 411 to 421,
Aëtius from 433 to 454 and
Ricimer from about 457 to 472. The year 476 is generally accepted as the formal end of the Western Roman Empire. That year,
Orestes, having stolen power from the emperor
Julius Nepos the year before, refused the request of Germanic mercenaries in his service for lands in Italy. The dissatisfied mercenaries, including the
Heruli, revolted. The revolt was led by the Germanic chieftain
Odoacer. Odoacer and his men captured and executed Orestes; weeks later they captured Ravenna and deposed Orestes' usurper son,
Romulus Augustus. This event has been traditionally considered the fall of the Roman Empire in the west. Odoacer quickly conquered the remaining provinces of Italy. Odoacer returned the western imperial regalia to the eastern emperor, Zeno. Zeno soon received two deputations. One was from Odoacer requesting that his control of Italy be formally recognised by the empire, in which case he would in turn acknowledge Zeno's supremacy. The other deputation was from Julius Nepos, requesting support to regain the throne. Zeno granted Odoacer the title
patrician. Zeno told Odoacer and the Roman Senate to take Nepos back, but Nepos never returned from Dalmatia, even though Odoacer issued coins in his name. Upon Nepos's death in 480, Zeno claimed Dalmatia for the East;
J. B. Bury considers this the real end of the Western Roman Empire. Odoacer attacked Dalmatia, and the ensuing war ended with
Theodoric the Great, King of the
Ostrogoths, conquering Italy under Zeno's authority and forming the
Ostrogothic Kingdom, with its capital at
Ravenna. ==Map gallery==