At least three aspects of the contemporary situation of Byzantium and Persia account for the phenomenal ease with which the Arabs overcame their enemies. First, both empires, exhausted by wars, had demobilized before 632. Second, both had ceased to support those client states on the frontiers of the Arabian Peninsula that had restrained the Bedouin of the desert for a century past. Third, and particularly in reference to Byzantium, religious controversy had weakened the loyalties that Syrians and Egyptians rendered to Constantinople. Heraclius had sought in 638 to placate miaphysite sentiment in those two provinces by promulgating the doctrine of monothelitism, holding that Christ, although of two natures, had but one will. Neither in the East nor in the West did that compromise prove successful. The victorious Muslims granted religious freedom to the Christian community in Alexandria, for example, and the Alexandrians quickly recalled their exiled miaphysite patriarch to rule over them, subject only to the ultimate political authority of the conquerors. In such a fashion the city persisted as a religious community under an Arab Muslim domination more welcome and more tolerant than that of Byzantium.
The aging Heraclius was unequal to the task of containing that new menace, and it was left to his successors—Constantine III (ruled February to May 641), Constans II (641–668), Constantine IV (668–685), and Justinian II (685–695, 705–711)—to do so. That bare list of emperors obscures the family conflicts that often imperiled the succession, but gradually the principle was established that, even if brothers ruled as coemperors, the senior’s authority would prevail. Although strife between Blues and Greens persisted throughout the century, internal revolt failed to imperil the dynasty until the reign of Justinian II. The latter was deposed and mutilated in 695. With the aid of the Bulgars, he returned in 705 to reassume rule and wreak a vengeance so terrible that his second deposition, and death, in 711 is surprising only in its delay of six years. From 711 until 717 the fortunes of the empire foundered; in that year Leo, stratēgos of the Anatolikon theme, arrived as a second Heraclius to found a dynasty that would rescue the empire from its new enemies, the Arab Muslims and the Bulgars.
Justinian II, gold solidus, 7th–8th century; in the British Museum.Peter Clayton
Three features distinguish the military history of the years 641–717: first, an increasing use of sea power on the part of the Arabs; second, a renewed threat in the Balkans occasioned by the appearance of the Onogur Huns, known in contemporary sources as the Bulgars; and third, a persisting interest among the emperors in their western possessions, despite the gradual attrition of Byzantine authority in the exarchates of Carthage and Ravenna. Thanks to the control that the Arabs gradually asserted over the sea routes to Constantinople, they climaxed their earlier assaults on Armenia and Asia Minor with a four-year siege of the great city itself (674–678). Defeated in that last attempt by the use of Greek fire, a flammable liquid of uncertain composition, the Arabs signed a 30-year truce, according to which they agreed to pay tribute in money, men, and horses. Lured by the unsettled conditions following Justinian’s second deposition, they renewed their assaults by land and sea, and in 717 the Arabs were again besieging Constantinople.
On the Balkan frontier, meanwhile, the Bulgars assumed the role abdicated by the Avars after 626. A pagan people whom the Khazars had forced toward the Danube Delta in the latter part of the 7th century, they eluded Constantine IV’s attempts to defeat them in 681. By virtue of a treaty signed in that year, as well as others dating from 705 and 716, the Bulgars were recognized as an independent kingdom, occupying (to the humiliation of Byzantium) lands south of the Danube into the Thracian plain. While the Bulgars had thus deprived the empire of control in the north and central Balkans, the Byzantines could take comfort in the expeditions of 658 and 688/689 launched, respectively, by Constans II and Justinian II into Macedonia and in the formation of the themes of Thrace (687) and Hellas (695). Those moves were evidence that Byzantine authority was beginning to prevail along the peninsular coastline and in certain parts of Greece where Slavs had penetrated.
In the West the situation was less reassuring. Monothelitism had evoked a hostile reception among the churches of North Africa and Italy, and the resulting disaffection had encouraged the exarchs of both Carthage (646) and Ravenna (652) to revolt. By the end of the century, Africa had been largely lost to Muslim conquerors who would, in 711, seize the last outpost at Septem. For the moment Sicily and the scattered Italian possessions remained secure. Constans undertook operations against the Lombards, and he apparently intended to move his capital to Sicily, before his assassination ended the career of the last Eastern emperor to venture into the West. In summary, Leo III in 717 ruled over an empire humiliated by the presence of pagan barbarians upon Balkan soil rightfully considered “Roman,” threatened by an attack upon its Anatolian heartland and its capital, and reduced, finally, in the West to Sicily and the remnants of the Ravenna exarchate.
However dismal the military record, institutional and economic developments had permitted the empire to survive and were to provide foundations for greater success in the centuries to come. The themal system had taken root and, with it, probably the institution of soldiers’ properties. Military service was a hereditary occupation: the eldest son assumed the burden of service, supported primarily by revenues from other members of the family who worked the land in the villages. That last was a task easier to accomplish at the end of the 7th century, thanks to the colonies of Slavs and other peoples taken into the empire and settled in the rural areas by Heraclius, Constantine IV, and Justinian II. In the 8th and 9th centuries, other emperors—including Leo III, Constantine V, and Nicephorus I—were to continue the practice, thus ending the population decline that had long eroded the ranks of Byzantine society. There are unmistakable signs of agricultural expansion even before 800, and, at about that time, urban life, which had never vanished in Asia Minor, began to flourish and expand in the Balkans. To judge from the evidence of the Farmer’s Law, dated in the 7th century, the technological base of Byzantine society was more advanced than that of contemporary western Europe: iron tools could be found in the villages; water mills dotted the landscape; and field-sown beans provided a diet rich in protein. None of those advances was to characterize western European agriculture until the 10th century. Byzantine agriculture enjoyed the further advantage of a highly developed tradition of careful farming that persisted even in the darkest days, enabling the peasant to make the most of the soil upon which he worked. The invasions had even provided a form of stimulus to development: having lost first its Egyptian granary and, later, its North African and Sicilian resources, the empire had to live essentially, although not totally, from whatever it could produce in the lands remaining to it. The invasions had also, in all probability, broken up many a large estate, and the small peasant holding seems to have been the “normal” form of rural organization in that period. Although collective village organization persisted in the form of the rural commune and, with it, certain collective agricultural practices, the state seems to have made little or no attempt to bind the peasant to the soil upon which the tax registers had inscribed him. While Byzantium remained a slave-owning society, the colonus of the later Roman Empire had vanished, and a greater degree of freedom and mobility characterized agricultural relationships during the 7th and 8th centuries.