The continued survival of the Eastern Roman Empire during the period 400-600, in contrast to the dissolution of the empire in the west traced in Chapter 7, depended on the continued viability of a strong central administration capable of extracting taxes from an economy that remained more urban, trade- connected, and vital than that of the west. Imperial territory included Egypt and, at times, at least parts of Mesopotamia, the richest provinces of the southwest Asian-Mediterranean world. That administration, in turn, supported a paid professional army and the construction of significant fortifications that protected vital towns, cities, and communications routes and provided bases for offensive action by the army. The heart of a system that was increasingly centralized lay in the imperial city of Constantinople, protected from the late fourth century onward by massive walls built by the emperor Theodosius (379-395).
The organization of the army itself reflected the reforms of Diocletian and Constantine in the decades around 300. The army consisted of two major types of units: the limitanei, or soldiers settled near the borders of provinces for local defense, whose connections with local society were strong; and a mobile central army designed for offensive action. The latter contained an increasing proportion of cavalry, reflecting both the need for mobility and offense and the fact that Rome’s major foe in the east, the Sassanid Persian Empire, depended heavily on cavalry forces. A significant Roman navy completed the military system of the empire and enhanced the strategic mobility of the field army.
The Walls of Constantinople
The Silvergate, a reconstructed section of the Theodosian land defenses of Constantinople, shows the multiple walls and towers that guarded the city for a thousand years.
The combination of financial resources, strong central control, professional forces, and a virtually impregnable capital allowed the Eastern Empire to weather invasions by Goths, Huns, and others (though often by bribing them to head west to the more vulnerable western provinces) and even, under Justinian (527-565), to go on the offensive against the Vandals in North Africa, the Visigoths in Spain, and the Lombards in Italy (Figure 8.1). But Justinian’s most important wars, and the training ground for his brilliant general Belisarius, were always against Persia, where simply maintaining the frontiers rather than expanding them was the realistic goal. And the cost of his expansionism was high in both economic and political terms. The financial and manpower resources of the empire were strained by constant warfare combined with massive building programs. In addition, Justinian had barely survived a massive revolt early in his reign and dealt autocratically with potential opposition thereafter. He was suspicious of rivals, which accounts in part, along with parsimony, for his forcing Belisarius to conduct his wars with minimal forces and even imprisoning him for a time for treason. His reign coincided with outbreaks of plague and probably some population decline that reduced the empire’s resources by the last quarter of the sixth century. By 600, Justinian’s legacy included a mounting crisis in renewed war with Persia, discussed further below.
Further, the continuity of Roman institutions was affected by two somewhat contradictory forces of change. First, the army tended increasingly in the east, as in the west, to recruit troops from among its barbarian foes, often incorporating them in large groups. This created an increasing gulf between the central mobile army and the society it protected. The consequences for the ideology of the army and its loyalty to Roman principles of politics tended to promote instability and alienation of social support for the state. But, second, the increasingly important ties between imperial government and the Christian Church, which had become by Theodosius’s time effectively a branch of government, especially in the east where imperial rule remained strong and undivided, tended to produce a more complicated set of effects. Christianity, as in the west, began to develop a set of ideologies condoning and even supporting war against heretics and unbelievers; in the Eastern Empire, this ideology became focused in the role of the emperor. Governance in general and military campaigns in particular gained in legitimation and potential popular support as a result. The church also constructed a second avenue, outside of official administrative channels and probably more tapped into popular culture, of organizing and administering the population. On the other hand, the dominance of Constantinople and a creed defined there in increasingly legalistic terms gave alternate (heretical) forms of Christianity political potential. The provinces of Syria and Egypt, whose patriarchs resented the claimed primacy of Constantinople, were by the late sixth century largely adherents of the Monophysite heresy (Monophysites denied the human part of Christ’s nature). The doctrinal details need not concern us, but the political effect was divisive, though its effect on the basic loyalty of the provinces to the empire is a matter of debate among historians and has probably been exaggerated. In the crisis after 600, the effects of Christianity would come decisively to outweigh those of a socially separated army.
Figure 8.1 Justinian's Conquests
That crisis involved increasingly bitter warfare with East Rome’s only superpower foe, the Sassanid Persian Empire. Persia, along with large but varying parts of Mesopotamia and regions to the east and north bordering India and the Central Asian steppes, respectively, had come gradually under Parthian control in the first century BCE, highlighted by the Parthian victory over Roman forces at Carrhae in 53 bce (see Chapter 4). The Parthians, originally steppe nomads, continued to dominate the area into the third century, though their political control was more in the way of a loose confederation than a unitary empire, and they generally acknowledged the superiority of Rome in upper Mesopotamia. Around 200, a series of civil wars seriously weakened Parthian power. Ardashir, governor of the central Persian region of Persis, consolidated his control of the heartland of Persian power in the decade after 200 and then challenged his Parthian overlords. By 226, he had defeated the Parthian ruler and proclaimed his dynasty, the Sassanids, as the successors of the Achaemenids of Cyrus the Great and Darius (see Chapter 2).
Ardashir thus reestablished a consciously Persian identity for the imperial power of southwest Asia, an identity intimately tied up with Zoroastrianism. Under the Achaemenids, this had been a predominantly elite religion that ruled tolerantly over a multitude of local religious traditions. But the Sassanids promoted Zoroastrianism in ways that, while retaining its vital ties to the Persian aristocracy and its legitimization of royal power and the Persian state, made it a more popular religion. Rulers encouraged conformity of practice and perhaps belief, developing an equation of Zoroastrianism not just with “Persianness” but with loyalty to the monarchy. This coincided with a rebuilding of Persian military power around a traditional core, the heavy cavalry forces of the Persian aristocracy, backed by infantry and archers drawn from the broader population and inspired by wider adherence to Zoroastrianism.
Sassanid Persia and East Rome went to war chronically between 230 and 600, usually struggling for control of the rich provinces of Mesopotamia, with the Persians dominating in the south and the Romans more successful in the north, nearer their bases in Asia Minor. Roman organization and military engineering, especially the strength of their fortifications, tended to be balanced fairly evenly against Persian advantages in mobility and cavalry skill and in theaters of conflict that lay closer to Persian centers of power than to Roman ones. The wars tended toward indecisiveness and often ended in a truce by mutual agreement to avoid fiscal crisis. Both empires also faced enemies on other fronts—East Rome in the Balkans and Persia in the borderlands to the Asian steppes to the north—that forced their attention elsewhere.
These wars in the last half of the sixth century became more intense, partly militarily but partly ideologically, as the clash of Christian and Zoroastrian universalisms fueled a rivalry that was already fierce simply on political and economic grounds. The Sassanids, in particular, learned lessons in organization and statecraft from their Roman neighbors. As a result, the political structure of the Sassanid Empire became, like East Rome’s, progressively more centralized over the course of the sixth century while, again like East Rome, its religious culture became more militant externally and more intolerant internally (though a host of smaller religious traditions continued to exist in the spaces between the great powers, especially in culturally heterogeneous and fragmented southern Mesopotamia).
The wars between Persia and Rome came to a climax between 603 and 628, with significant consequences for each empire and for subsequent world history. Sparked by mutual interference in each other’s dynastic disputes, Chosroes II of Persia opened the wars against the emperor Phocas, who murdered his own predecessor, Maurice, who had helped Chosroes gain the Sassanid throne. But with initial success against an East Rome both politically divided—Heraclius overthrew Phocas in 610, assuming command of Roman forces—and threatened by a major Avar invasion in the Balkans, Chosroes’s ambitions grew. By 615, he had conquered Syria and Armenia, the latter a major Roman recruiting area; then, between 616 and 619, he conquered Egypt, cutting off Constantinople’s main grain source. With forces established across the Bosporus from Constantinople in 616, Chosroes allied with the Avars; the new allies approached the mighty city in 619. East Rome was on the verge of extinction, and the empire of Darius on the verge of being reestablished.
Heraclius nearly fled to Africa, but a religious revival led by the patriarch Sergius convinced him to stay, and the church then provided resources for rebuilding the Roman position. Heraclius bought off the Avars and used his naval superiority to renew the war in Syria, drawing the Persians away from his capital. Then, in a daring and brilliant series of campaigns between 623 and 627—during which Constantinople was besieged in 626—he bypassed the reconquest of the provinces completely, striking directly into the heart of Persia. At the decisive battle of Nineveh in 627, he routed the Persian army and pursued the survivors to the gates of the Persian capital of Ctesiphon. The Persians killed Chosroes, installed his son Kavadh II as king, and accepted terms that returned all of Chosroes’s conquests to Roman rule.
It was an amazing recovery, but one that was to be undone rapidly from an unforeseen quarter, in part by the consequences of the sort of warfare each side waged, for both the religious and political impact of the wars spread beyond the confines of the two empires. Some historians have come to call Heraclius’s campaigns against the Persians the first “crusade” because of the importance that Christianity assumed for the morale and fighting spirit of the troops under his command. They marched with crosses on their banners, and the notion of being surrounded by enemies but backed by God contributed to a growing sense in Constantinople that the eastern Christians were a Chosen People. But, of course, similar sentiments opposed the Romans on the other side: These wars could be considered both the first and the last Zoroastrian crusades. At the same time, both sides, given the desperation of the struggle, looked for any allies they could find. The Avars played this role for a time for the Persians, but for the most part, both sides looked to Arab client kingdoms to the south for manpower and diversionary attacks. The result was a flow into Arabia of wealth in the form of bribes to enemies and subsidies to allies, linked to intense ideological pressure in the form of monotheistic religions. This inflow prepared the ground for surprising state formation and religious creativity by one Arab leader in particular, the Prophet Muhammad. What the resulting Arab religious state would meet were two exhausted empires and provinces in Syria and Egypt only recently reintegrated into the structures of Roman rule.