History of the Roman Empire disputes about the supreme authority, this finally formalised a peaceful succession of the emperor: in each half a "Caesar" would rise up to replace the "Augustus" and select a new "Caesar". On May 1, 305, Diocletian and Maximian abdicated in favour of their "Caesars". Galerius named the two new "Caesars": his nephew Maximinus for himself, and Flavius Valerius Severus for Constantius. The arrangement worked well under Diocletian and Maximian and shortly thereafter. The internal tensions within the Roman government were less acute than they had been. In "The Decline and Fall of the Roman Empire", Edward Gibbon notes that this
Historiography of the fall of the Western Roman Empire to the fall of the West Roman Empire (395-476), in his book "The Fall of the West: The Slow Death of the Roman Superpower" (2009). William H. McNeill, a world historian, noted in chapter three of his book "Plagues and Peoples" (1976) that the Roman Empire suffered the severe and protracted Antonine Plague starting around 165 AD. For about twenty years, waves of one or more diseases, possibly the first epidemics of smallpox and measles, swept through the Empire, ultimately killing about half the population. Similar epidemics, such as the Plague of Cyprian, also occurred in the 3rd century. McNeill