This is a history of the Roman empire from the accession of Valentinian in 364 to the death of Marcian in 457, a period of turbulence and radical change, by the end of which the Empire had fragmented. The Roman rulers, whether legitimate emperors or usurpers, sought above all to meet the challenges to the Empire's unity posed by barbarian invasions, religious conflict and political rivalry. Despite impressive achievements, ultimately they failed. How and why they did so, and why the Roman state endured in the East and failed in the west, are key questions posed in this book. These formidably complicated issues have exercised the minds of scholars for a very long time. Mark Humphries draws on his own extensive primary research, as well as on recent and established published work, to provide a full and rounded interpretation. In doing so he examines the interactions the eastern and western churches in the period, whose rivalry and fragmentation parallels (and was itself a factor in) the dissolution of the empire. He also considers the important developments (especially under Theodosius I) in law and administration, and the effects of invasion and civil war on economic and social life.