Diocletian established the Tetrarchy, a system by which the Roman Empire was divided into East and West, with each having an Augustus to rule over it and a Caesar to assist him.

From Diocletian's Tetrarchy reform, the provinces were organized into dioceses each administered by a vicarius.

Alternatively, a more idiomatic style may develop into an equally prestigious tradition of titles, because of the shining example of the original – thus various styles of Emperors trace back to the Roman Imperator ( strictly speaking a republican military honorific ), the family surname Caesar ( turned into an imperial title since Diocletian's Tetrarchy ).

In 293, this system was further developed into the Tetrarchy: Maximian was elevated to the rank of Augustus and both Augusti appointed junior sub-emperors with the title Caesar.

Before Constantine's death, he divided the Empire into four parts governed by caesares, apparently intending to re-establish the Tetrarchy.

Diocletian divided the Empire into four parts ( dioceses ), the so-called Tetrarchy.

It developed into the economic capital of Roman Pannonia and later became one of the four capital cities of the Roman Empire during the Tetrarchy.

The history of the empire before the Tetrarchy is portrayed as a time of civil war, savage despotism, and imperial collapse.

Diocletian tried to solve this problem by re-establishing an adoptive succession with a senior ( Augustus ) and junior ( Caesar ) emperor in each half of the Empire, but this system of Tetrarchy broke down within one generation ; the hereditary principle was re-established with generally unfortunate results, and civil war was thereafter the main method of establishing new imperial regimes.

Although Emperor Diocletian is held to have strengthened the navy, and increased its manpower from 46, 000 to 64, 000 men, the old standing fleets had all but vanished, and in the civil wars that ended the Tetrarchy, the opposing sides had to mobilize the resources and commandeered the ships of the Eastern Mediterranean port cities.

On 20 November, he celebrated, with Maximian, the twentieth anniversary of his reign ( vicennalia ), the tenth anniversary of the Tetrarchy ( decennalia ), and a triumph for the war with Persia.

This Tetrarchy lasted until c. 313, when internecine conflict eliminated most of the claimants to power, leaving Constantine in the West and Licinius in the East.

* September 18 – Battle of Chrysopolis: Constantine I definitively defeats Licinius at Chrysopolis, and becomes sole Emperor, thus ending the period of the Tetrarchy.

* November 11 – The Congress of Carnuntum: Attempting to keep peace within the Roman Empire, the leaders of the Tetrarchy declare Maxentius a public enemy and Licinius is proclaimed Augustus, while rival contender Constantine I is declared Caesar of Britain and Gaul.

Constantine won the battle and started on the path that led him to end the Tetrarchy and become the sole ruler of the Roman Empire.

* 324 – 325: Emperor Constantine wins the Civil Wars of the Tetrarchy ( 306 – 324 ) and reunites the empire.

* 311 – The Edict of Toleration by Galerius was issued in 311 by the Roman Tetrarchy of Galerius, Constantine and Licinius, officially ending the Diocletian persecution of Christianity.

* Civil wars of the Tetrarchy ( 306 – 324 ), between the co-emperors of the Roman Empire, starting with the usurpation of Maxentius and the defeat of Severus, and ending with the defeat of Licinius at the hands of Constantine I.

To seal the alliance between them for control of the Tetrarchy, in 307 Maximianus married her to Constantine I, who set aside his wife Minervina in her favour.

A Western Roman Empire existed intermittently in several periods between the 3rd and 5th centuries, after Diocletian's Tetrarchy and the reunifications associated with Constantine the Great and Julian the Apostate ( 324 – 363 ).

The system of the Tetrarchy quickly ran aground when the Western Roman Empire's Constantius died unexpectedly in 306, and his son Constantine the Great was proclaimed Augustus of the West by the legions in Britain.

In 308, the Augustus of the East, Galerius, arranged a conference at Carnuntum which revived the Tetrarchy by dividing the West between Constantine and a newcomer named Licinius.

Following the victory of Christian emperor Constantine in the Civil Wars of the Tetrarchy ( 306 – 324 ), the Christianization of the Roman Empire began, and in 326, Constantine's mother Saint Helena visited Jerusalem and began the construction of churches and shrines.

This left Constantine as the sole emperor, ending the period of the Tetrarchy.

Tiberias was founded sometime around 20 CE in Herodian Tetrarchy of Galilee and Peraea by the Roman Jewish client king Herod Antipas, son of Herod the Great.

* Tetrarchy ( Judea ), formed by the sons of Herod the Great

The Great Persecution officially ended in April 311, when Galerius, senior emperor of the Tetrarchy, issued an edict of toleration, which granted Christians the right to practice their religion, though it did not restore any property to them.

The Tetrarchy was quickly abandoned as a system ( though the four quarters of the empire survived as praetorian prefectures ) in favour of two equal, territorial emperors, and the previous system of Emperors and Emperors-designate was restored, both in the Latin-speaking West and the Greek-speaking East.

The orbis terrarum was central to the iconography of the Tetrarchy, representing the Tetrarchs ' claim of having restored security to the Roman world.

The Tetrarchy | Tetrarchs were the four co-rulers who governed the Roman Empire as long as Diocletian's reform lasted.

The underlying causes of the battle were the rivalries inherent in Diocletian's Tetrarchy.

Since Diocletian's Tetrarchy ( 296 ), it was the major province of a diocese confusingly called Galliae (' the Gaul s '), to which further only the Helvetic, Belgian ( both also Celtic ) and German provinces belonged ; with the dioceses of Viennensis ( the southern provinces of Gaul ), Britanniae ( also Celtic ) and Hispaniae ( the whole Celtiberian peninsula ) this formed the praetorian prefecture also called Galliae, subordinate to the western emperor.

He served with distinction as a soldier under Emperors Aurelian and Probus, and in 293 at the establishment of the Tetrarchy, was designated Caesar along with Constantius Chlorus, receiving in marriage Diocletian's daughter Valeria ( later known as Galeria Valeria ), and at the same time being entrusted with the care of the Illyrian provinces.

Since emperor Diocletian's Tetrarchy reform ( 293 ), the country was further divided in three provinces, as the small, easternmost region Sitifensis was split off from Mauretania Caesariensis.

Since Emperor Diocletian's Tetrarchy reform c. 300, it was part of the diocese of Oriens, in the praetorian prefecture of the same name.

In Diocletian's Tetrarchy, the traditional seniorities were maintained: Augustus was reserved for the two senior emperors and Caesar for the two junior emperors-each delegated a share of power and responsibility but each an emperor-in-waiting, should anything befall his senior.

Under Diocletian's Tetrarchy reform, the easternmost part was broken off as a tiny separate province, Sitifensis, called after its inland capital Sitifis ( Sétif ) with a significant port at Saldae ( presently Béjaïa ).

During the Tetrarchy ( Emperor Diocletian's reform of Roman governmental structures in 296 ), Mauretania Tingitana became part of the Diocese of Hispaniae, ' the Spains ', and, by extension, part of the Praetorian Prefecture of the Gauls.

The term Tetrarchy ( Greek: " leadership of four ") describes any form of government where power is divided among four individuals, but in modern usage usually refers to the system instituted by Roman Emperor Diocletian in 293, marking the end of the Crisis of the Third Century and the recovery of the Roman Empire.

Nicomedia was the metropolis of Bithynia under the Roman Empire, and Diocletian made it the eastern capital city of the Roman Empire in 286 when he introduced the Tetrarchy system.

Nicomedia was the metropolis of Bithynia under the Roman Empire ( see Nicaea ), and Diocletian made it the eastern capital city of the Roman Empire in 286 when he introduced the Tetrarchy system.

On March 1, 293, Gaius Aurelius Valerius Diocletianus established the Tetrarchy, a system of rule by two senior Emperors and two junior sub-Emperors.

Moving the notion of the Emperor away from the republican forms of the Empire's first three centuries, Diocletian introduced a novel system of joint rule by four monarchs, the Tetrarchy.

The Tetrarchy was a system established by Diocletian to facilitate effective government of the Empire.

* Emperor Diocletian attempted an elaborate system with four emperors ( two seniors styled Augustus, each with a junior styled Caesar ), called the Tetrarchy.

Diocletian instituted a number of reforms designed to stabilize the empire and the imperial office, including a collegial system of emperors called the Tetrarchy, bringing an end to the Third Century Crisis and inaugurating the Dominate era of Roman history.

He urged the public to see his reign and his governing system, the Tetrarchy ( rule by four emperors ), as a renewal of traditional Roman values and, after the anarchic third century, a return to the " Golden Age of Rome ".