Saint Donatian and his younger brother Rogatian were natives of Nantes who lived in the fourth century AD. At the time, the ruler of the Western Roman Empire was Diocletian. Since Octavian had established the principate, Rome had shifted from a republic to an empire, and Diocletian was the one who completed the final step of that transformation. He stripped the Senate of the Directory of its last real powers, turning it into nothing more than an honorary decoration.
At the same time, he established the system of tetrarchy, dividing the empire into eastern and western halves. Each half was governed by an emperor called an "Augustus," and each Augustus appointed an assistant and heir called a "Caesar."
He first granted his comrade Madame Maxime the title of Caesar, then elevated her to Augustus, making her co-emperor of the Roman Empire and ruler of its western half, while Diocletian planted cabbages at his palace in Salona by the Adriatic Sea.
Diocletian's father had been a slave and was later freed. After Caracalla abolished the tradition requiring legionary soldiers to be citizens, Diocletian was able to join the army as the son of a lower-class laborer. He accumulated military merit and eventually became the sole ruler of the Roman Empire.
He was tired. At fifty-five, he chose to retire, becoming the only Roman emperor to voluntarily relinquish the throne and power. He had designed the tetrarchy to resolve the empire's disputes. In his plan, he and Madame Maxime would abdicate at the same time, while Galerius and Constantius I would both rise from Caesar to Augustus. But people in Italy disliked their ruler Severus II, so they elected Madame Maxime's son as emperor.
Signs of civil war had already appeared. The emperors had no time to manage religious affairs, leaving them