Drastic decreases in population throughout the western parts of the empire, along with a general degradation of society within the cities, exacerbated the crisis leading to a shortage of labor.

Administrative control was brought under the auspices of the emperor, and the whole of Italia was relegated to the status of a regular province, now also compelled to pay taxes.

The Praetorian prefecture of the East (Praefectura praetorio per Orientem) was made up of five dioceses- Aegyptus, Oriens, Pontus, Asiana, and Thracia.

The Persian Sassanids had grown more menacing in their quest for previous territory, and the barbarians were becoming a more serious problem along the lower part of the Danube.

Judging the threats to be of dire importance, Diocletian took up residence in Nicomedia, where he established his capital there, leaving Maximian, his co-emperor, in charge of the West.

To combat inflation he introduced the solidus, a gold coin that became the standard for Byzantine and European currencies for more than a thousand years.

The Roman army was reorganised to consist of mobile field units and garrison soldiers capable of countering internal threats and barbarian invasions.

Constantine pursued successful campaigns against the tribes on the Roman frontiers—the Franks, the Alemanni, the Goths, and the Sarmatians—even resettling territories abandoned by his predecessors during the Crisis of the Third Century.

The Church of the Holy Sepulchre was built on his orders at the purported site of Jesus' tomb in Jerusalem and became the holiest place in Christendom.

The resulting conflict left Constantine II dead and Constans as ruler of the west until he was overthrown and assassinated in 350 by the usurper Magnentius.

Following his death, the Roman forces were obliged to cede territory in order to escape, including the fortress city of Nisibis.

"Valens was utterly undistinguished, still only a protector, and possessed no military ability: he betrayed his consciousness of inferiority by his nervous suspicion of plots and savage punishment of alleged traitors," writes A.H.M.