After fifty years of civil war, plague, and invasion had split the empire in three, a soldier-emperor reunites it by force in under five years.
By A.D. 270 the Roman empire had very nearly come apart. Half a century of murdered emperors, debased coinage, plague, and invasion across the Rhine, Danube, and eastern frontier had broken it into three: a breakaway Gallic empire in the west, the realm of Palmyra under Zenobia in the east, and a shrinking centre. In under five years the emperor Aurelian reunited all three — defeating the Juthungi and Goths on the Danube, marching east to take Palmyra and recover Egypt, and finally receiving the surrender of the Gallic empire at Châlons.
The coinage of these years tells the deeper crisis: the silver denarius had been debased almost to copper, and prices rose accordingly — the inflation that Diocletian would later try to freeze by edict. Aurelian both reformed the coinage and, for the first time in centuries, walled the city of Rome itself.
Scroll to follow Aurelian’s reconquest of the breakaway Gallic and Palmyrene empires and the reunification of Rome.
When Aurelian is acclaimed emperor by the Danubian legions at Sirmium, the Roman world has splintered. In the west, the breakaway Gallic Empire controls Britain, Gaul, and Spain under Tetricus. In the east, Queen Zenobia rules Egypt and the Levant from Palmyra. Aurelian inherits only Italy and the Balkans — with barbarian invaders already massing along the Alps.
The Germanic Juthungi cross the Po and ambush Aurelian’s army in the woods of Placentia. With Rome gripped by terror, Aurelian regroups: he halts the invaders at Fanum Fortunae on the Adriatic and annihilates them at Ticinum (Pavia). To ensure the capital can never again be taken by surprise, he orders the construction of the colossal, nineteen-kilometer Aurelian Walls.
Aurelian marches north to the Danube, crushing a Gothic invasion and killing their king Cannabaudes. Facing military reality on an exposed northern frontier, he makes the hard strategic choice to evacuate Trajan’s old province of Dacia north of the river, resettling the legions and population south of the Danube into Moesia. With the northern border consolidated, he turns his full strength east.
Crossing into Asia at Byzantium, Aurelian retakes Bithynia and spares Tyana after a vision of Apollonius. At Antioch, on the lake of Immae, his light cavalry feigns retreat to exhaust Zenobia’s famed heavy cataphracts before turning to cut them to pieces. Another crushing victory at Emesa shatters the Palmyrene army and opens the desert road to Palmyra itself.
Aurelian besieges Palmyra across waterless desert. Zenobia attempts to flee on swift dromedaries to seek Persian aid but is captured on the banks of the Euphrates; Palmyra yields. When the city rebels months later, Aurelian returns and sacks it. Concurrently, his general Probus recovers Alexandria and Egypt, restoring the empire’s wealthiest granary to Roman control.
Marching west to Gaul, Aurelian confronts the Gallic emperor Tetricus near Châlons. Tetricus secretly defects to Aurelian, and his mutinous army is subdued. Gaul and Britain submit without further slaughter. In late 274, Aurelian enters Rome in the most spectacular Triumph in generations, parading Zenobia and Tetricus in golden chains. The Senate bestows on him the title Restitutor Orbis — Restorer of the World.
Sites: Pleiades. Land, lakes and rivers: Natural Earth (public domain). Campaign routes and breakaway frontiers are schematic — no precise ancient itineraries survive; reconstructed after Zosimus, the Historia Augusta, and Zonaras. Realm boundaries are labels only.
Aurelian earned the title restitutor orbis, restorer of the world, and was murdered by his own officers in 275 before he could finish the work. The lasting repair of the empire’s government would fall to Diocletian a decade later.
Civil wars and breakaway empires, a new Persia, a second capital in the East, and the western provinces lost to the kingdoms.
Commodus' successor Pertinax is murdered by the praetorians after 87 days, and Didius Julianus buys the throne from them. Three armies name their own emperors: Septimius Severus on the Danube, Pescennius Niger in Syria, Clodius Albinus in Britain. Severus reaches Rome first and buys off Albinus with the title of Caesar. Niger holds the East as far as the Bosporus.
Niger is beaten at Cyzicus, Nicaea and finally Issus (194); Byzantium holds out against Severus into 195. Albinus proclaims himself emperor and dies after a great battle outside Lugdunum (197). Severus then turns on Parthia, sacks Ctesiphon, and makes northern Mesopotamia a province with its capital at Nisibis, garrisoned by two new legions.
In 208 Severus takes his sons and a large army to Britain, repairs Hadrian's Wall and campaigns deep into Scotland against the Caledonians and Maeatae. He dies at Eburacum in February 211, advising his sons, as Dio reports it, to agree, to enrich the soldiers and to scorn everyone else. Caracalla and Geta make peace and go home.
Caracalla murders Geta and in 212 makes almost every free inhabitant of the empire a Roman citizen. He annexes the kingdom of Edessa and is killed near Carrhae (217). In 224 Ardashir overthrows the last Parthian king and founds the Sasanian dynasty of Persia. In 235 Severus Alexander is murdered by his own troops near Mogontiacum.
Emperors now rise and fall with their armies; some twenty are recognised in fifty years. Shapur I of Persia claims a victory over Gordian III (244) and takes a large payment from his successor Philip. In 250 the Goths under Cniva cross the Danube. The next summer they trap and kill Decius and his son at Abritus, the first emperor to fall to a foreign enemy.
Shapur takes Antioch and destroys Dura; in 260 he captures the emperor Valerian near Edessa, and Valerian dies a prisoner. In the West the Rhine army proclaims Postumus, whose Gallic empire holds Gaul, Britain and for a time Spain. The lands between the Rhine and the Danube are given up, and Gallienus beats the Alamanni near Mediolanum.
Odaenathus of Palmyra, loyal to Gallienus, drives the Persians back and rules the East for Rome until his murder (267). His widow Zenobia, governing for their son Vaballathus, takes Egypt (270) and pushes into Asia Minor. Spain has returned to the central emperor. The new emperor, Aurelian, beats the Juthungi in Italy and begins a wall round Rome.
Aurelian marches east, beats Zenobia's army at Immae and Emesa (272) and takes Palmyra; when it rebels the next year he sacks it. In 274 Tetricus, the last Gallic emperor, surrenders at Châlons. Aurelian evacuates Dacia north of the Danube, giving its name to new provinces south of the river, and is murdered in Thrace in 275.
Diocletian, emperor from 284, shares power with Maximian (286), and in 293 the two add Caesars, Constantius and Galerius. They govern from cities near the frontiers, such as Trier, Milan, Sirmium and Nicomedia. Italy is divided into provinces and taxed like the rest. In Britain the fleet commander Carausius has ruled as emperor since about 286; his murderer Allectus holds on until 296.
Constantius recovers Britain (296); Galerius beats the Persian king Narseh (298) and gains lands beyond the Tigris. After Diocletian abdicates (305) the tetrarchy breaks down. Constantine, hailed at Eburacum in 306, defeats Maxentius at the Milvian Bridge (312) and Licinius (324). In 330 he dedicates his new capital, Constantinople, on the site of Byzantium.
Constantine's sons divide the empire and fight over it; Constantius II spends years holding the eastern frontier against Shapur II, who takes Amida (359). Julian invades Persia in 363 and reaches Ctesiphon, but dies of a wound in the retreat. To save the army, his successor Jovian surrenders Nisibis, Singara and the lands beyond the Tigris.
In 376, driven west by the Huns, the Tervingi Goths ask to cross the Danube and Valens admits them. Starved and cheated by Roman officials, they revolt. On 9 August 378 they destroy Valens and much of the eastern army outside Adrianople; the emperor's body is never found. The Goths range through Thrace until Theodosius makes peace with them (382).
Theodosius settles the Goths inside the empire as allies under their own leaders (382). After beating the usurper Eugenius at the Frigidus (394) he is briefly the last emperor to rule both halves, and dies at Mediolanum in January 395. His sons divide the empire: Arcadius at Constantinople, Honorius, aged ten, in the West. The two courts soon go their own ways.
At the end of 406, by tradition on the last day of the year, Vandals, Alans and Suebi cross the Rhine; by 409 they are in Spain. The army of Britain makes Constantine III emperor and takes Gaul. Alaric's Goths, refused land and pay, besiege Rome three times and on 24 August 410 sack it. Honorius, safe in Ravenna, can send Britain no help.
The Visigoths are settled in Aquitaine as allies (418), with their capital at Tolosa. Under Gaiseric the Vandals cross from Spain to Africa (429), besiege Hippo, where Augustine dies in 430, and on 19 October 439 take Carthage, the West's richest city. In Spain the Suebi take Emerita. Aetius, the West's general, holds Gaul with Hunnish troops.
Attila leads the Huns into Gaul in 451 and is checked by Aetius and the Visigoths on the Catalaunian Plains; the next year he destroys Aquileia and turns back from Italy. He dies in 453. Valentinian III murders Aetius (454) and is murdered in turn (455). Weeks later Gaiseric's fleet reaches Rome, and the Vandals plunder it for two weeks.
Nine emperors follow in twenty-one years, most made by generals. In 476 the soldiers in Italy, refused land, raise Odoacer as king. He deposes the boy Romulus, sends the imperial regalia to Constantinople, and rules Italy acknowledging the emperor there. Visigoths, Burgundians, Franks and Vandals share the western provinces; Julius Nepos, the last western emperor, holds only Dalmatia.
Province outlines: Ancient World Mapping Center, “Roman Empire c. 60 BC”, “c. AD 117 extent” and “c. AD 200 extent and provinces” (ODbL; after the Barrington Atlas). Each territory is drawn at its c. 60 BC or c. AD 200 extent from the date it came under Roman rule, so earlier inland limits are drawn too large. Changes after A.D. 200 are drawn on the AD 200 provinces, so a province is coloured whole even where only part of it was lost, shared or settled; Mesopotamia after 363 kept a western strip. The fifth-century kingdoms are labels only: their borders are not drawn. Invasion arrows are schematic. Coastlines and rivers: Natural Earth. Sites: Pleiades.