Many consider Emperor Constantine I (reigned 306–337) to be the first "Byzantine Emperor". It was he who moved the imperial capital in 324 from Nicomedia to Byzantium, refounded as Constantinople, or Nova Roma ("New Rome"). The city of Rome itself had not served as the capital since the reign of Diocletian. Some date the beginnings of the Empire to the reign of Theodosius I (379–395) and Christianity's official supplanting of the pagan Roman religion, or following his death in 395, when the political division between East and West became permanent. Others place it yet later in 476, when Romulus Augustulus, traditionally considered the last western Emperor, was deposed, thus leaving sole imperial authority with the emperor in the Greek East. Others point to the reorganization of the empire in the time of Heraclius (ca. 620) when Latin titles and usages were officially replaced with Greek versions. In any case, the changeover was gradual and by 330, when Constantine inaugurated his new capital, the process of hellenization and increasing Christianization was already under way. The Empire is generally considered to have ended after the fall of Constantinople to the Ottoman Turks in 1453. The Plague of Justinian was a pandemic that afflicted the Byzantine Empire, including its capital Constantinople, in the years 541–542. It is estimated that the Plague of Justinian killed as many as 100 million people across the world. It caused Europe's population to drop by around 50% between 541 and 700. It also may have contributed to the success of the Arab conquests.