284–305

Diocletian's reforms and the establishment of the Tetrarchy

For decades in the 3rd century there was military anarchy, as the army made and unmade emperors. Diocletian came to power in 284 and restored stability by dividing power.

In 285 he made Maximian co-ruler in the West. In 293 he added two junior co-rulers, the Caesars Constantius Chlorus and Galerius. This created a system of four rulers, the Tetrarchy, under which a military coup lost its point.

Alongside this, Diocletian reformed the army, taxation and administration. These reforms secured the empire roughly two more centuries of existence. At first these changes, like the preceding "Peace of Gallienus," also benefited the Church.

Yet the same centralization of power and drive for religious uniformity would later, under that same Diocletian, lead to the harshest persecution of Christians. This was the Great Persecution, which began in 303.