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In 285 Diocletian divided the Roman Empire in a western and eastern part, assigning the latter to himself.
Establishment
January 286: The first phase of the Tetrarchy, sometimes referred to as the Diarchy ('the rule of two'), involved the designation of the general Maximian as co-emperor of Diocletian.
Chronology
Interactive Chronologies with maps are available in the section Changes Navigation
Were a series of Wars between Rome (first the Roman Republic then the Roman Empire and finally the Eastern Roman Empire) and Persia (the Parthian Empire, and then its successor, the Sasanian Empire). The wars were ended by the early Muslim conquests, which led to the fall of the Sasanian Empire and huge territorial losses for the Byzantine Empire.
1.1.Sasanian Campaign of Galerius
Was a military campaign by Roman Emperor Galerius against the Sasanian Empire.
January 297: Narses, to punish the Romans for supporting the Armenian revolt, invaded the Roman province of Syria.
January 298: After two battles with uncertain outcome, the third battle (fought between Carre and Nicephorium or Callinicum) was a complete defeat for the Romans, following which Rome lost the province of Mesopotamia.
January 299: Diocletian assembled a cover army in Syria, ready to go into action in an emergency. Taking advantage of the advantage, he took the city of Ctesiphon.
1.1.1.Peace Treaty of Diocletian with the Sasanian Empire
Was a peace treaty between the Roman Empire under Diocletian (in the East) and the Sasanian Empire.
January 300: Diocletian and Galerius, after meeting in Nisibis, sent Sicorio Probus, one of their secretaries, to communicate the conditions for peace to the Persians. When the day of the audience finally arrived, Probus communicated the conditions for peace to the Shah: Armenia and Iberia became client kingdoms of the Romans; the border between the two empires is fixed on the Tigris river while the border between Armenia and Persia is fixed near Zintha, a fortress of Media on the border with Armenia; The Persians cede five regions beyond the Tigris. According to Peter Patrick, these were Intelene, Sophene, Arzanene, Zabdicene and Carduene. According to Ammianus Marcellinus, however, the five regions ceded would have been Zabdicene, Arzanene, Moxoene, Carduene and Rehimene. Narses only opposed the first point, which however he was forced to accept in the face of the firmness of the Romans. After the treaty was made, relatives who had been taken captive by the Romans were returned to Narses.
Was a peace treaty of Roman Emperor Diocletian with the Nubian Nobatae and Blemmyes tribes that moved Rome's borders north to Philae.
January 299: Diocletian travelled south along the Nile the following summer, where he visited Oxyrhynchus and Elephantine. In Nubia, he made peace with the Nobatae and Blemmyes tribes. Under the terms of the peace treaty Rome's borders moved north to Philae.
Were a series of conflicts between the co-emperors of the Roman Empire (the system of Thetrarchy introduced by Diocletian divided the Roman Empire between two emperors, the augusti, and their junior colleagues and designated successors, the caesares). The war ended with Constantine I as undisputed Emperor.
January 306: The senior Roman emperors jointly abdicated and retired in 305 AD, allowing Constantius and Galerius to be elevated in rank to Augusti. They in turn appointed two new Caesars - Severus in the west under Constantius, and Maximinus Daia in the east under Galerius.
3.1.Early Tetrarchic Period
The Tetrarchy was the system instituted by Roman emperor Diocletian in 293 AD to govern the ancient Roman Empire by dividing it between two emperors, the augusti, and their junior colleagues and designated successors, the caesares. This marked the end of the Crisis of the Third Century.
January 294: In 293, feeling more focus was needed on both civic and military problems, Diocletian, with Maximian's consent, expanded the imperial college by appointing two Caesars.
Disestablishment
January 306: The senior Roman emperors jointly abdicated and retired in 305 AD, allowing Constantius and Galerius to be elevated in rank to Augusti. They in turn appointed two new Caesars - Severus in the west under Constantius, and Maximinus Daia in the east under Galerius.
Diocletian: East
