The Gallic Empire under Tetricus I by 271 A.D. (in green)
|Capital||Colonia Agrippina (260–271), Augusta Treverorum (271–274)|
|Languages||Latin (popular), Local languages such as Gaulish, British, other languages that survived into this period.|
|-||270–274||Tetricus II (Caesar)|
|Historical era||Late Antiquity|
It was founded by Postumus in 260 in the wake of barbarian invasions and instability in Rome, and at its height included the territories of Germania, Gaul, Britannia, and (briefly) Hispania. After Postumus' assassination in 268 it lost much of its territory, but continued under a number of emperors and usurpers. It was retaken by Roman Emperor Aurelian after the Battle of Châlons in 274.
The Crisis of the Third Century began as Emperor Valerian was defeated and captured by the Sassanid Empire of Persia, leaving his son Gallienus in very shaky control. Shortly thereafter, the Palmyrene Empire, which came to encompass Egypt, Syria, Judea, and Arabia Petraea also broke away.
The governors in Pannonia staged unsuccessful local revolts. The Emperor left to the Danube to attend to their disruption. This left Postumus, who was governor of Germania Superior and Inferior, in charge at the Rhine border. The imperial heir Saloninus and the praetorian prefect Silvanus remained at Colonia Agrippina (Cologne), to keep the young heir out of danger and perhaps also as a control on Postumus' ambitions. Before long, however, Postumus besieged Colonia Agrippina and put the young heir and his guardian to death. Postumus established his capital at Cologne.
The Gallic Empire had its own senate, two annually elected consuls (not all of the names of the consuls have survived) and its own praetorian guard. Postumus himself seems to have held the office of consul five times.
Postumus successfully fended off Gallienus in 263, and was never challenged by him again. However, in early 268 he was challenged by Laelianus, probably one of his commanders, who was declared Emperor at Mogontiacum (Mainz) by his Legio XXII Primigenia. Postumus quickly retook Mogontiacum and Laelianus was killed. However the success meant little and he was overthrown and killed by his own troops, reportedly because he did not allow them to sack the city.
After Postumus 
After the death of Postumus, the Gallic Empire began to fall apart. Roman Emperor Claudius Gothicus re-established Roman authority in Gallia Narbonensis and parts of Gallia Aquitania, and there is some evidence that the provinces of Hispania, which did not recognize the subsequent Gallic Emperors, may have re-aligned with Rome.
Marcus Aurelius Marius was instated as Emperor upon Postumus' death, but died very shortly after; the literary sources say he reigned only two days, though it is more likely he reigned for a few months. Subsequently Victorinus came to power, being recognized as Emperor in northern Gaul and Britannia, but not in Hispania. Victorinus spent most of his reign dealing with insurgencies and attempting to recover the Gaulish territories taken by Claudius Gothicus. He was assassinated in 271, but his mother Victoria took control of his troops and used her power to influence the selection of his successor. With Victoria's support, Tetricus I was made Emperor, and was recognized in Britannia and the parts of Gaul still controlled by the Empire. Tetricus fought off Germanic barbarians who had begun ravaging Gaul after the death of Victorinus, and was able to re-take Gallia Aquitania and western Gallia Narbonensis while Roman Emperor Aurelian was engaging Queen Zenobia's Palmyrene Empire in the east. He established the imperial court at Trier, and in 273 he elevated his son, Tetricus II, to the rank of Caesar. The following year Tetricus II was made co-consul, but the Empire grew weak from internal strife, including a mutiny led by the usurper Faustinus. By that time Aurelian had defeated the Palmyrene Empire and had made plans to re-conquer the west. He moved into Gaul and defeated Tetricus at the Battle of Châlons in 274; according to the sources, Tetricus, weary of the in-fighting, offered to surrender in exchange for clemency for him and his son. This detail may be later propaganda, but either way, Aurelian was victorious, and the Gallic Empire was effectively dismantled.
Beyond a mere symptom of chaos in the third century crisis, the Gallic Empire can be interpreted as a measure of provincial identification competing with the traditional sense of romanitas, of the cohesive loyalties of individual legions, and of the power accumulated by entrenched Romanized aristocratic kinship networks whose local power bases ranged from the Rhine to Baetica, although the extent of "Gaulish" self-identification that nationalist historians have inferred is probably inflated.[neutrality is disputed] Postumus declared his sole intention was to protect Gaul – this was his larger Imperial task – and in 261 he repelled mixed groups of Franks and Alamanni to hold the Rhine limes secure, though lands beyond the upper Rhine and Danube had to be abandoned to the barbarians within a couple of years.
The usurpation of Britain and Northern Gaul under Carausius just twenty years later reflects this trend. Local loyalties from the landed aristocracy and deteriorating morale in the legions enabled him to seize power in Britain, in an attempt to carve out a "Britannic" Empire based on the Roman model in Britain and Northern Gaul. Similarly with the withdrawal of legions after 408, many Britons desired a localized Roman authority rather than nationalist revolt. The desire for Roman order and institutions was therefore entirely compatible with a degree of national separatism.
Gallic Emperors 
The Gallic Emperors are known primarily from the coins they minted. The political and military history of the Gallic Empire can be sketched through their careers. Their names are as follows:
- Postumus 260 – 268 (including joint rule with his son Postumus Junior ? – 268)
- (Laelianus 268, usurper)
- Marius 268
- Victorinus 268 – 270
- (Domitianus 271? usurper)
- Tetricus I 270 – 274 (residence Trier)
See also 
- Bourne, R. J. (2001) Aspects of the relationship between the Central and Gallic Empires in the mid to late third century AD with special reference to coinage studies. Archaeopress. p. 22.
- Aurelius Victor 33.8; Eutropius 9.9.1.
- Polfer, Michel (June 3, 2000). "Victorinus (A.D. 269–271)". De Imperatoribus Romanis: An Online Encyclopedia of Roman Rulers and Their Families. Retrieved July 10, 2009.
- Weigel, Richard D. (June 19, 2001). "Claudius II Gothicus (268–270)". De Imperatoribus Romanis: An Online Encyclopedia of Roman Rulers and Their Families. Retrieved July 10, 2009.
- Polfer, Michael (June 24, 1999). "Marius (A.D. 269)". De Imperatoribus Romanis: An Online Encyclopedia of Roman Rulers and Their Families. Retrieved July 10, 2009.
- Polfer, Michel (January 28, 2000). "Tetricus I (AD 271–273)". De Imperatoribus Romanis: An Online Encyclopedia of Roman Rulers and Their Families. Retrieved July 10, 2009.