Gibbon begins The Decline and Fall of the Roman Empire with a picture of the Roman Empire at its apparent height. He describes the second century CE of the Roman Empire as a golden age. At that time, the Roman Empire included “the most civilized portion of mankind,” whose “peaceful inhabitants enjoyed and abused the advantages of wealth and luxury” (1). As Gibbon explains, by the second century the Roman Empire had reached its greatest extent, failing only to expand into Ethiopia, the Arabian Peninsula, Ireland, and modern-day Scotland. However, the second-century emperor Trajan did try to push the empire’s borders even further. After a five-year war, he conquered the territories of Decebalus, king of the Decian people in modern-day Romania, establishing a new province called Decia. Also, he defeated the Parthian Empire based in Iran and made new imperial provinces of Armenia, Assyria, and Mesopotamia.

After Trajan’s death, however, his successor Hadrian gave up all of these provinces except Decia, and reestablished the Euphrates River as the eastern boundary of the Roman Empire. Hadrian and the two emperors who followed him, Antoninus Pius and Marcus Aurelius, “persisted in the design of maintaining the dignity of the empire, without attempting to enlarge its limits” (8).