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
Structural history of the Roman military off deep in the enemy's rear. Simultaneously, barbarian troops in Rome's pay came to be "in a condition of almost perpetual turbulence and revolt" from 409 onwards. In 476 these troops finally unseated the last emperor of the Western Roman Empire. The Eastern Roman forces continued to defend the Eastern Roman (Byzantine) Empire until its fall in 1453. The former Oxford University historian Adrian Goldsworthy has argued that the cause of the fall of the Roman Empire in the West should not be blamed on barbarization of the late Roman Army, but on its recurrent civil wars, which led to