The Crisis of the Third Century was a period in which the Roman Empire nearly collapsed under the combined pressures of invasion, civil war, plague, and economic depression.
Facing the pressures of civil war, plague, invasion, and economic depression, Diocletian was able to stabilize the Roman empire for another hundred years through economic reform and the establishment of the Tetrarchy.
Though the early Christians were persecuted under emperors such as Nero and Diocletian, the religion continued to thrive and grow, eventually becoming the official religion of the Roman Empire under Constantine.
Constantine the Great was a Roman Emperor from 306 to 337 AD who adopted Christianity and declared it the religion of the Roman Empire.
Constantine built a new imperial residence in Byzantium and renamed the city Constantinople after himself, which would later become the capital of the Empire for over one thousand years.
The Fall of the Western Roman Empire was the period of decline in the Western Roman Empire in which it disintegrated and split into numerous successor states.