quadrumvirate n : a group of four men

This article is mainly on the Tetrarchy created in the Roman by Diocletian. For the tetrarchy formed from the kingdom of Herod the Great see Tetrarchy (Judea) Although power was shared in the Tetrarchic system, the public image of the four emperors in the imperial college was carefully managed to give the appearance of a united empire (patrimonium indivisum). This was especially important after the civil war of the third century.

The Tetrarchs appeared identical in all official portraits. Coinage dating from the Tetrarchic period depicts every emperor with identical features - only the inscriptions on the coins indicate which one of the four emperors is being shown. The Portrait of Four Tetrarchs porphyry sculpture (pictured at right), now standing at the south-west corner of St. Mark's Basilica in Venice, shows the Tetrarchs again with identical features and wearing the same military costume.

Military successes

One of the greatest problems facing emperors in the Third Century Crisis was that they were only ever able to personally command troops on one front at any one time. While Aurelian and Probus were prepared to accompany their armies thousands of miles between war regions, this was not an ideal solution. Furthermore, it was risky for an emperor to delegate power in his absence to a subordinate general, who might win a victory and then be proclaimed as a rival emperor himself by his troops (which often happened). All members of the imperial college, on the other hand, were of essentially equal rank, despite two being senior emperors and two being junior; their functions and authorities were also equal.

Under the Tetrarchy a number of important military victories were secured. Both the Dyarchic and the Tetrarchic system ensured that an emperor was nearby to every crisis area to personally direct and remain in control of campaigns simultaneously on more than just one front. After suffering a defeat by the Persians in 296, Galerius crushed Narseh in 298 - reversing a series of Roman defeats throughout the century - capturing members of the imperial household, a substantial amount of booty and gaining a highly favourable peace treaty, which secured peace between the two powers for a generation. Similarly, Constantius defeated the British usurper Allectus, Maximian pacified the Gauls and Diocletian crushed the revolt of Domitianus in Egypt.

Fall of the Tetrarchy

Confusion and collapse

When in 305 the 20-years reign term of Diocletian and Maximian ended, both abdicated. Their Caesares, Galerius and Constantius Chlorus, were both raised to the rank of Augustus, and two new Caesares were appointed: Maximinus (Caesar to Galerius) and Flavius Valerius Severus (Caesar to Constantius). These four formed the second Tetrarchy.

However, the system broke down very quickly thereafter. When Constantius died in 306, Galerius promoted Severus to Augustus while Constantine I was proclaimed Augustus to succeed his father Constantius, by his father's troops. At the same time, Maxentius, the son of Maximian, resented having been left out of the new arrangements, defeated Severus before forcing him to abdicate and then arranging his murder in 307. Maxentius and Maximian both then declared themselves Augusti. By 308 there were therefore no fewer than four claimants to the rank of Augustus (Galerius, Constantine, Maximian and Maxentius), and only one to that of Caesar (Maximinus).

In 308 Galerius, together with the retired emperor Diocletian and the supposedly-retired Maximian, called an imperial 'conference' at Carnuntum on the River Danube, which agreed that Licinius would become Augustus in the West, with Constantine as his Caesar. In the East, Galerius remained Augustus and Maximinus remained his Caesar. Maximian was to retire, and Maxentius was declared an usurper. This agreement proved disastrous: by 308 Maxentius had become de facto ruler of Italy and Africa anyway, even if he was deprived of imperial rank; neither Constantine nor Maximinus - who had both been Caesares since 305 - were prepared to tolerate the promotion of the Augustus Licinius as their superior.

After an abortive attempt to placate both Constantine and Maximinus with the meaningless title filius Augusti ('son of the Augustus', which could have been an alternative title for Caesar, as either implied the right to succeed), they both had to be recognised as Augusti in 309. However, four full Augusti all at odds with each other did not bode well for the Tetrarchic system.

End of the Tetrarchy

Between 309 and 313 most of the claimants to the imperial office died or were killed in various internecine wars. Constantine arranged Maximian's death by strangulation in 310. Galerius died naturally in 311. Maxentius was defeated by Constantine at the Battle of the Milvian Bridge in 312 and subsequently killed. Maximinus committed suicide at Tarsus in 313 after being defeated in battle by Licinius.

By 313, therefore, there remained only two emperors: Constantine in the West and Licinius in the East. The Tetrarchic system was at an end, although it took until 324 for Constantine to finally defeat Licinius, reunite the two halves of the Roman empire and declare himself sole Augustus.

Legacy

Although the Tetrarchic system as such only lasted until c. 313, many aspects survived. The fourfold regional division of the empire continued in the form of Praetorian prefectures, each of which was overseen by a praetorian prefect and subdivided into administrative dioceses, and often reappeared in the title of the military supra-provincial command assigned to a magister militum.

The pre-existing notion of consortium imperii, the sharing of imperial power, and/or the — in the theoretical republic still unconstitutional — notion that an associate to the throne was the designated successor (possibly conflicting with the notion of hereditary claim by birth or adoption), was to reappear repeatedly.

The idea of the two halves, the East and the West, re-emerged and eventually resulted in the permanent de facto division into two separate Roman empires after the death of Theodosius I (though it is important to remember that the Empire was never formally divided, Emperors of East and West legally ruling as one imperial college till the fall of Rome's western empire left Byzantium, the 'second Rome', sole direct heir).

Lesser Tetrarchies

• Tetrarchies in the ancient world existed in both Thessaly (in northern Greece) and Galatia (in central Asia Minor; including Lycaonia).
• The constellation of Jewish principalities in Roman Palestine: for instance, Herod Antipas ruled Galilee and Perea as a tetrarch (so styled in the gospel of Matthew, but rendered as king in the Gospel of Mark).
• At a number of modern American universities, tetrarchy is the preferred format for student government, based on the model established at the University of Virginia with the governing body known as HJM.

See also

• Augustus (honorific)
• Caesar (title)
• Consortium imperii

References

External links

• A detailed chronology of the tetrarchy and a convenient chart.

Sources

(incomplete)

• Notitia dignitatum, a later document from the imperial chancery
• Pauly-Wissowa, Realencyclopädie der Klassischen Altertumswissenschaft