Its subject is the fate of one of the world's greatest civilizations over thirteen centuries - its rulers, wars and society, and the events that led to its disastrous collapse. Here, in volumes three and four, Gibbon vividly recounts the waves of barbarian invaders under commanders such as Alaric and Attila, who overran and eventually destroyed the West. He then turns his gaze to events in the East, where even the achievements of the Byzantine emperor Justinian and the campaigns of the brilliant military leader Belisarius could not conceal the fundamental weaknesses of their empire.