By the late 5th century, Zosimus (also called "Zosimus the Historian"; fl. 490s–510s: a Byzantine historian who lived in Constantinople) could see the writing on the Roman wall, and asserted that empires fell due to internal disunity. He gave examples from the histories of Greece and Macedonia. In the case of each empire, growth had resulted from consolidation against an external enemy; Rome herself, in response to Hannibal's threat posed at Cannae, had risen to great-power status within a mere five decades. With Rome's world dominion, however, aristocracy had been supplanted by a monarchy, which in turn tended to decay into tyranny; after Augustus Caesar, good rulers had alternated with tyrannical ones. The Roman Empire, in its western and eastern sectors, had become a contending ground between contestants for power, while outside powers acquired an advantage. In Rome's decay, Zosimus saw history repeating itself in its general movements.