The first millennium of the anno Domini or Common Era was a millennium spanning the years 1 to 1000 (1st to 10th centuries; in astronomy: JD 1721425.5 – 2086667.5). The world population rose more slowly than during the preceding millennium, from about 200 million in the year 1 to about 300 million in the year 1000.
In Western Eurasia (Europe and Near East), the first millennium was a time of great transition from Classical Antiquity to the Middle Ages. The 1st century saw the peak of the Roman Empire, followed by its gradual decline during the period of Late Antiquity, the rise of Christianity and the Great Migrations. The second half of the millennium is characterized as the Early Middle Ages in Europe, and marked by the Viking expansion in the west, and the continuation of the Byzantine Empire (Eastern Roman Empire) in the east.