Beginning of a timeline
Just my own idea for a possible alternate timeline along these lines ...
C. 282 AD – an 8 year old boy named Flavius Valerius Constantinus, son of an officer named Constantius in the Roman army, dies after a sudden illness.
303 AD – Emperor Diocletian launches the last and largest persecution of Christians within the Roman Empire
305 AD Emperor Diocletian abdicates as Emperor, leaving a system of 2 senior emperors and 2 junior emperors that he hopes will ensure a stable succession (which it totally fails to do)
306 AD Constantius dies in the province of Britannia with no son to succeed him
314 – 316 War between Maxentius, ruler of the western Empire, and Licinius, ruler of the Eastern Empire. Licinius is ultimately victorious as many of Maxentius’ troops are disaffected and change sides. Believing that he can not rule the entire empire at once, Licinius appoints Aurelius Valens as co-emperor, responsible for the western part of the empire.
317 – Licinius and Valens issue a general edict of religious toleration, ending the last persecution of Christians (which had been less and less common in the previous few years)
319 – 321 A series of synods are held by the various Christian communities, the main ones being in Antioch, Alexandria, Nicomedia, Carthage, and Rome. They attempt to reach agreement on many questions of doctrine and practice, with very limited success.
325 – Licinius decides to adopt Nicomedia in Asia Minor as his permanent capital, and pushes ambitious building projects in the city. In the west, Valens does much the same thing with Augusta Trevirorum in eastern Gaul, and Mediolanum in northern Italy.
328 – Licinius dies suddenly, leaving the throne to his young son Magentius. The “power behind the throne†in the east is actually Martinianus, who holds the position of Magister Officiorum.
329 – Martinianus deposes Magentius, has him placed under house arrest, and later quietly murdered when he is out of the public view. For some reason, Martinanus also becomes suspicious of the loyalty of the Christians in the eastern empire, and renews the persecution.
330 – Valens invades the eastern empire, declaring his intention to overthrow the murderer and usurper Martinianus.
331 – 332 Valens defeats Martinianus’ forces in a series of battles and sieges, until Martinianus flees with a few followers to the Persians. Most Christians in the eastern Empire welcome the victory of Valens, which ends the renewed persecutions.
333 – Valens decides to stay in the Eastern Empire, and leaves his capable young son Aurelian II in charge of the western empire. He keeps Nicomedia as his eastern capital, but also plans to enlarge and strengthen the nearby city of Byzantium, along the Bosphorus straits. In the recent war, his troops faced a difficult siege at that place, and were only able to capture it due to treachery on the part of one of the garrison’s officers.
334 – 337 Valens fights wars against the Persians. Martinianus sneaks back into the Empire and attempts to raise a revolt, but he is captured and executed.
337 In Alexandria, tension rises between rival groups of Christians, the Arians and Athanasians, who have opposing views on the nature of Christ. When rioting breaks out, imperial garrison troops have to quell the rebellion. Valens issues an edict instituting tough penalties for anyone disturbing the peace over religious disputes.