The highpoint of Justinian’s reign was the recapture of Italy and the overthrow of the Ostrogothic Kingdom in 552.
However, even at this high-water mark in the revival of the Roman Empire, we see the seeds of the future collapse of Roman power.
Plague had already broken out in the Mediterranean in the 540s and the death toll may have been as high as around a third of the population of the empire. Even so, Justinian’s tax collectors were so efficient that the coffers of the state continued to be filled and the money ensured that Roman arms were able to retake the southern portion of Visigothic Spain. At Justinian’s death in 565 the empire was larger again than at any time since the collapse of the Western Empire in the 460s and 470s.
However, this expansion had been at a huge cost in financial terms, as well as in manpower and in the impact of the Gothic Wars on the Italian peninsula. Also, to create the armies that conquered Spain, Italy and North Africa, Justinian transferred troops from the Danubian and Persian frontiers. When the human cost of the plague is added in, we see a decline in both the number and the quality of the troops and a general replacement of frontier forces with fortifications. We also see a change in the tactics of the Roman military with heavy cavalry becoming more and more important in the field armies and with diplomacy being used more and more as an instrument of state.
However, the real legacy of Justinian’s reign was that he took the empire of Constantine and his successors and remade it as a different type of state.
In his turning away from the traditional ruling classes of Constantinople and in his changes to the government which emphasised the central role of the figure and majesty of the emperor, Justinian created the basis for the mediaeval Byzantine Empire, with a court ruled by elaborate protocol and with a renewed emphasis on the central role of religion and imperial power. Justinian increased the focus on the capital to such an extent that the provincial elites went into a decline that was accompanied by a rise in the power of the bishops and the rural landowners and we see an end to those local town and city councils that were a feature of urban life in Late Antiquity.
After Justinian’s death, his imperial reconquests came under renewed threats, from the nomadic Avars across the Danube, from the Germanic Langobards or Lombards in Italy and from a revitalised Sassanian Persia.
Within a dozen years the Lombards had conquered much of Italy and the Avars were challenging Roman control of the Balkans. Justinian’s patrimony was simply too extended, too unwieldy and too expensive to maintain to be a viable entity in the radically changed world of the later 6th century.
Justinian’s immediate successor, his nephew Justin II soon became embroiled in costly wars against the Persians, leading to a loss of Roman territory. Justin eventually became unable to rule because of his increasing mental instability and he was replaced as emperor by the general Flavius Tiberius Constantinus who ruled as Tiberius II. His short reign was marked by a renewal of Slav incursions into the Balkans, by a Persian invasion and by his emptying of the imperial coffers in an orgy of expenditure.
He was replaced on his death by the emperor Maurice, who was able to defeat the Persians and bring stability to the East before turning his attentions to the Danubian border and the Balkans, where his armies were able to defeat the Avars and Gepids, as well as crushing the Slavs.
Unfortunately Maurice was not popular with his armies in the Balkans who mutinied in 602, murdering Maurice and his family and raising their own candidate, Flavius Phocas, to the purple.
Phocas ruled for a mere eight years, seeing his frontiers come under renewed pressure from the Avars and Slavs, leading to the loss of the Danubian provinces and in 608, the Exarch of Africa, Heraclius the Elder, rebelled against Phocas, his son Heraclius leading an army to Constantinople where he was able to overthrow Phocas and become the next emperor.
Heraclius’ reign was one of those turning points in world history and deserves its own post, so I shall end here with just a few comments.
The loss of the western reconquests of Justinian and the shift in emphasis to wars in the Balkans and against the perennial threat from the Persians marks the beginning of the end of the Roman Empire’s role as a power in western Europe, from now on the concerns of the empire lie in the Near and Middle East. The loss of most of Italy meant that although there would continue to be a Byzantine presence in western Europe and the western Mediterranean for several centuries to come, the centre of the empire has firmly shifted eastwards. The western presence becomes an issue on the periphery of the empire, rather than one of central importance.
To grasp this is of major importance in the way that we should understand the mediaeval empire and its importance in the development of Christendom and the European identity.