of the Third Century, with the shift towards a more openly autocratic and ritualized form of government, the adoption of Christianity as the state religion, and a general rejection of the traditions and values of Classical Antiquity. While traditional historiography emphasized this break with Antiquity by using the term "Byzantine Empire" instead of Roman Empire, recent schools of history offer a more nuanced view, seeing mostly continuity rather than a sharp break. The Empire of Late Antiquity already looked very different from classical Rome. The Roman Empire emerged from the Roman Republic when Julius Caesar and Augustus Caesar transformed it from a republic into a monarchy. Rome reached its zenith in the 2nd century, then fortunes slowly declined (with many revivals and restorations along the way). The reasons for the decline of the Empire are still debated today, and are likely multiple. Historians infer that the population appears to have diminished in many provinces—especially western Europe—from the diminishing size of fortifications built to protect the cities from barbarian incursions from the 3rd century on. Some historians even have suggested that parts of the periphery were no longer inhabited because these fortifications were restricted to the center of the city only. Tree rings suggest "distinct drying" beginning in 250. By the late 3rd century, the city of Rome no longer served as an effective capital for the Emperor and various cities were used as new administrative capitals. Successive emperors, starting with Constantine, privileged the eastern city of Byzantium, which he had entirely rebuilt after a siege. Later renamed Constantinople, and protected by formidable walls in the late 4th and early 5th centuries, it was to become the largest and most powerful city of Christian Europe in the Early Middle Ages. Since the Crisis of the Third Century, the Empire was intermittently ruled by more than one emperor at once (usually two), presiding over different regions. At first a haphazard form of power sharing, this eventually settled on an east–west administrative division between the Western Roman Empire (centered on Rome, but now usually presided from other seats of power such as Trier, Milan, and especially Ravenna), and the Eastern Roman Empire (with its capital initially in Nicomedia, and later Constantinople). The Latin-speaking west, under dreadful demographic crisis, and the wealthier Greek-speaking east, also began to diverge politically and culturally. Although this was a gradual process, still incomplete when Italy came under the