Diocletian and the Tetrarchy

Diocletian rises from the common soldiers and takes power after half a century of turmoil. So that one man need not be on the Danube and the Euphrates at once, he divides the government: two senior rulers, the Augusti, and two junior, the Caesars, each with his own territory and residence — and Rome ceases to be the city where the emperor lives. The provinces are split and multiplied, tax is assessed on units of land and heads, and an edict attempts to hold down prices — in vain. Under him, too, comes the last and heaviest persecution of the Christians; and in 305 he lays down power of his own will, which no one before him had done.