Following the turbulent third century, the Emperor Diocletian (r. 284-305) issued a series of reforms which stabilized and irrevocably changed the Roman Empire. Prior to his reign, the imperial government had made few demands upon its citizenry and most of its functions were performed by local officials. But inflation skyrocketed in the third century and the army was undermanned and poorly supplied. Diocletian greatly expanded both the imperial bureaucracy and the military. He augmented tax revenues through more rigorous assessment and collection and tried to stem inflation by freezing prices. He fought shortages in labor and production by making many occupations related to military production hereditary: sons would have to take their fathers' jobs whether they wanted to or not. These reforms helped create the heavier-handed, more militarized Empire of Late Antiquity. Since economic and military crises were averted, many scholars have praised Diocletian's reforms, but his contemporary Lactantius gives us a glimpse of how the typical Roman citizen may have viewed them.

Finding the third-century Empire too vast and beset with turmoil to rule alone, Diocletian, in one of his major reforms, deicided not to rule alone. He created the tetrarchy, a system of four emperors, two senior Augusti and their subordinates and eventual successors, the Caesares. Each Augustus had responsibility for one half the Empire, Diocletian choosing the wealthier east. The Augusti would choose their Caesares on the basis of personal ability, not family connection. Diocletian hoped to solve the succession struggles that had plagued the Empire in this fashion. It worked briefly, but after Diocletian died the relatives of the retired Augusti made war on their appointed successors, plunging the Empire into conflict. A more lasting legacy was division and multiple emperors ruling simultaneously, sometimes in conflict and sometimes not. This sculpture shows the tetrachs in idealized form.

Constantine considered himself “the restorer of the Roman Empire” since he unified it following the collapse of Diocletian’s tertarchy. The militarization of the Empire continued under him as he expanded the use of mobile field armies staffed primarily by barbarians. His numerous treaties with German tribes initiated a policy of conciliation and alliance which eventually led to the formation of barbarian kingdoms within the Western Empire. The reforms of Diocletian and Constantine created a more stable empire, but one which was very distinct from its predecessor.

In 378 the Roman Empire suffered its first major defeat at the hands of the barbarians. Pushed westward by the Huns, the Visigoths crossed the Danube and entered the Empire in the northern Balkans in the 370s. Exploited by local Roman officials and unable to reach a permanent settlement with the Eastern Emperor Valens (r. 364-378), the Visigoths rebelled and defeated his forces at Adrianople. The Visigoths continued to be a thorn in the Empire’s side, even sacking Rome itself in 410, until they received imperial permission to establish their own kingdom in southern Gaul in 418. Thus the battle of Adrianople represents the first step in the transformation from Empire to independent kingdoms in the West.

In this amusing letter, written around 460, Sidonius Apollinaris (c. 430-c. 479) chastises his friend Syagrius for learning the language of the barbarians who settled in late Roman Gaul. Sidonius, whose family had held high administrative posts in Gaul for generations, epitomized classical culture. While dismayed at his friend’s decision, Sidonius acknowledges the necessity of speaking German for a late fifth-century man of affairs. This begrudging acknowledgment illustrates the profound political and demographic changes which occurred as the Western Empire stumbled toward oblivion.

The Visigoths were the first barbarian people to enter the late Empire en masse in 376 and the first to found their own kingdom, based in southern Gaul, within the boundaries of the Western Empire in 418. Subsequent barbarian tribes established kingdoms in the western imperial provinces of Africa (the Vandals), northern Gaul (the Franks), and Italy (the Ostrogoths). By the time that this crown was created for the Visigothic king Recceswinth (r. 653-72), the Franks had driven the Visigoths out of Gaul, thus creating the embryo of the later kingdom of France. The Visigoths moved south of the Pyrenees and ruled in Spain until they succumbed to Islamic forces in the early eighth century.

The Emperor Justinian (r. 527-565) is justly remembered as the greatest ruler of Late Antiquity. While imperial authority had collapsed in the West, Justinian reinvigorated the Eastern Empire. His legal and religious reforms and the conquest of the former Roman provinces of Italy and Africa are applauded below by the contemporary historian Procopius, writing around 560. However, Procopius reserves his greatest praise for the Emperor’s role in the construction of the great church Hagia Sophia (b. 532-537) in Constantinople, thus illustrating how completely Christian the world of Late Antiquity had become.

The Empress Theodora (d. 548), wife of Justinian, was one of the most remarkable women of Late Antiquity. Before she married into the purple she had been an actress, a term often employed at the time as an euphemism for an even less reputable profession. A brave and intelligent woman, she became one of her husband’s key advisors. As Procopius relates below, she persuaded her husband not to flee when the people of Constantinople revolted early in his reign. This was called the Nika Insurrection because the rioters shouted "Nika!" (victory). The excerpt, written about twenty years later, also demonstrates the factional disputes which plagued most of the cities of the time period.

Two mosaics of Justinian and Theodora, situated above and on either side of the altar of the church of San Vitale in Ravenna, Italy, are the only surviving visual representations of this famous couple. Following his conquest of Italy, Justinian commissioned these works as symbols of the imperial restoration in the heartland of the old Empire. Their position above the altar captured the attention of any worshipper. The fact that the mosaic of the empress is of equal size and prominence as that of her husband exemplifies the ruling partnership that the two had formed.

The law code of Justinian has had an immeasurable impact upon Western Civilization. The code collected and organized over a thousand years of Roman legislation. It was accompanied by two other works: the Digest, containing the works of many Roman jurists, and the Institutes, which served as an introductory textbook for law students. The legal systems of almost every modern Western nation owe a profound debt to Justinian’s code. The following excerpt from the Institutes makes some basic distinctions between different types of laws and describes the functions of various institutions within the Roman legal system.

Shapur I (r. 240-72), represented here on a silver and gilt presentation dish, began the rule of the Sassinid dynasty in Persia. An ancient foe of Rome, the Persian Empire had been quiescent in the years before the Sassanids’ ascendancy. The ambitious new dynasty wreaked havoc on Rome’s eastern frontiers. Shapur captured the Roman emperor Valerian in 260 and used him as a human stepladder for mounting and dismounting his horse. The conflict between Persia and Rome continued into the seventh century. In an era when Roman emperors sought to contain the barbarian threat to their northern frontier, the Persian menace meant that they often faced war on more than one front.

Procopius, a scathing critic of the Emperor Justinian (r. 527-565), provides an unflattering portrait of the condition of the Byzantine Empire, its treatment of its soldiers, and the conditions along the frontiers with the Sassanian Persians and the borderlands of northern Arabia.

The reign of the Eastern, or Byzantine, Emperor Heraclius (r. 610-641) witnessed a long war against the Sassanid Persian Empire. At first the Persians had the upper hand, conquering many Byzantine provinces and taking what was thought to be the true cross from Jerusalem. Ultimately, Heraclius prevailed and, in a scene described below by the seventh-century Armenian historian Sebeos, returned the cross in triumph to Jerusalem. With the defeat of their ancient enemy, the Byzantine Empire seemingly reached new heights. However, the desperate struggle left both the victorious Byzantines and the defeated Persians too exhausted to effectively counter the followers of Muhammad when they unexpectedly broke out of Arabia in 634.

Inspired by earlier interpretations of Rome's decline offered by Gibbon, historians such as Michael Rostovtzeff attempted to explain the causes of the collapse within the late antique period. In these excerpts from his 1928 Oxford University Press history, Rostovtzeff argues that the ancient world grew old and decrepit from within during late antiquity, and that the period saw no great artistic or political achievements of any significance.

For centuries the deposition of the last Western Roman Emperor in 476 was considered to be one of the major turning points of history. With this event the classical world ended and the Middle Ages began. Only with the works of Peter Brown and other historians of the ‘Late Antique’ school did the idea of a very gradual transition and of great continuities spanning the centuries around 476 emerge. In this view the late antique period represents a crucial era in the formation of ideas and structures that continue to shape today's world.