History of the Roman Empire founder of the brief Flavian dynasty, to be followed by the Nerva–Antonine dynasty which produced the "Five Good Emperors": Nerva, Trajan, Hadrian, Antoninus Pius and the philosophically inclined Marcus Aurelius. In the view of the Greek historian Dio Cassius, a contemporary observer, the accession of the emperor Commodus in 180 AD marked the descent "from a kingdom of gold to one of rust and iron"—a famous comment which has led some historians, notably Edward Gibbon, to take Commodus' reign as the beginning of the decline of the Roman Empire. In 212, during the reign of Caracalla, Roman citizenship was granted
Historiography of the fall of the Western Roman Empire the Huns as deeply significant in the fall of the Western Empire long before they themselves became a military threat to the Empire. He postulates that the Hunnic expansion caused unprecedented immigration in 376 and 406 by barbarian groupings who had become significantly more politically and militarily capable than in previous eras. This impacted an empire already at maximum stretch due to the Sassanid pressure. Essentially he argues that the external pressures of 376–470 could have brought the Western Empire down at any point in its history. He disputes Gibbon's contention that Christianity and moral decay led to the decline.