Until Heraclius arrived to save the empire in 610, inconsistency and contradiction marked the policies adopted by the emperors, a reflection of their inability to solve the problems Justinian had bequeathed his successors. Justin II (565–578) haughtily refused to continue the payment of tribute to Avar or Persian; he thereby preserved the resources of the treasury, which he further increased by levying new taxes. Praiseworthy as his refusal to submit to blackmail may seem, Justin’s intransigence only increased the menace to the empire. His successor, Tiberius II (578–582), removed the taxes and, choosing between his enemies, awarded subsidies to the Avars while taking military action against the Persians. Although Tiberius’s general, Maurice, led an effective campaign on the eastern frontier, subsidies failed to restrain the Avars. They captured the Balkan fortress of Sirmium in 582, while the Turks began inroads across the Danube that would take them, within 50 years, into Macedonia, Thrace, and Greece.

The accession of Maurice in 582 inaugurated a reign of 20 years marked by success against Persia, a reorganization of Byzantine government in the West, and the practice of economies during his Balkan campaigns that, however unavoidable, would destroy him in 602. Byzantine efforts against Sāsānian Persia were rewarded in 591 by a fortunate accident. The lawful claimant to the Persian throne, Khosrow II, appealed to Maurice for aid against the rebels who had challenged his succession. In gratitude for this support, Khosrow abandoned the frontier cities and the claims to Armenia, the two major sources of contention between Byzantium and Persia. The terms of the treaty gave Byzantium access, in Armenia, to a land rich in the soldiers it desperately needed and, equally important, an opportunity to concentrate on other frontiers where the situation had worsened.

Confronted by a Visigothic resurgence in Spain and by the results of a Lombard invasion of Italy (568)—which was steadily confining Byzantine power to Ravenna, Venice, and Calabria-Sicily in the south—Maurice developed a form of military government throughout the relatively secure province of North Africa and in whatever regions were left in Italy. He abandoned the old principle of separating civil from military powers, placing both in the hands of the generals, or exarchs, located, respectively, at Carthage and Ravenna. Their provinces, or exarchates, were subdivided into duchies composed of garrison centres that were manned not by professional soldiers but by conscript local landholders. The exarchate system of military government seems to have worked well: North Africa was generally quiet despite Moorish threats, and in 597 the ailing Maurice had intended to install his second son as emperor throughout those western possessions in which he had clearly not lost interest.

But the major thrust of his efforts during the last years of his reign was to be found in the Balkans, where, by dint of constant campaigning, his armies had forced the Avars back across the Danube by 602. In the course of those military operations, Maurice made two mistakes: the first weakened him, and the second destroyed him together with his dynasty. Rather than constantly accompanying his armies in the field, as his 7th- and 8th-century successors were to do, Maurice remained for the most part in Constantinople, losing an opportunity to engage the personal loyalty of his troops. He could not count on their obedience when he issued unwelcome commands from afar that decreased their pay in 588, ordered them to accept uniforms and weapons in kind rather than in cash equivalents, and, in 602, required the soldiers to establish winter quarters in enemy lands across the Danube, lest their requirements prove too great a strain on the agricultural and financial resources of the empire’s provinces south of the river. Exasperated by that last demand, the soldiers rose in revolt, put a junior officer named Phocas at their head, and marched on Constantinople. Again becoming politically active, the Blues and the Greens united against Maurice, and the aged emperor watched as his five sons were slaughtered before he himself met a barbarous death.

The ensuing reign of Phocas (602–610) may be described as a disaster. Khosrow seized the opportunity offered him by the murder of his benefactor, Maurice, to initiate a war of revenge that led Persian armies into the Anatolian heartland. Subsidies again failed to restrain the barbarians north of the Danube; after 602 the frontier crumbled, not to be restored save at the cost of centuries of warfare. Lacking a legitimate title, holding his crown only by right of conquest, Phocas found himself confronted by constant revolt and rebellion. To contemporaries, the coincidence of pestilence, endemic warfare, and social upheaval seemed to herald the coming of the Antichrist, the resurrection of the dead, and the end of the world.

But it was a human saviour who appeared, albeit under divine auspices. Heraclius, son of the exarch of Africa, set sail from the western extremes of the empire, placing his fleet under the protection of an icon of the Virgin against Phocas, stigmatized in the sources as the “corrupter of virgins.” In the course of his voyage along the northern shores of the Mediterranean, Heraclius added to his forces and arrived at Constantinople in October 610 to be hailed as a saviour. With the warm support of the Green faction, he quickly bested his enemy, decapitating Phocas and, with him, those Phocas had advanced to high civil and military office. There were, in consequence, few experienced counselors to aid Heraclius, for, among the men of prominence under Phocas—and earlier under Maurice—few survived to greet the new emperor.

Heraclius and the origin of the themes

The most-threatening problem Heraclius faced was the external menace of the Avars and the Persians, and neither people abated that pressure during the first years of the new reign. The Avars almost captured the emperor in 617 during a conference outside the long walls protecting the capital. The Persians penetrated Asia Minor and then turned to the south, capturing Jerusalem and Alexandria (in Egypt). The great days of the Persian Achaemenid empire seemed to have come again, and there was little in the recent history of the Byzantine emperors that would encourage Heraclius to place much faith in the future. He clearly could not hope to survive unless he kept under arms the troops he had brought with him, yet the fate of Maurice demonstrated that that would be no easy task, given the empire’s lack of financial and agricultural resources.

Three sources of strength enabled Heraclius to turn defeat into victory. The first was the pattern of military government as he and the nucleus of his army would have known it in the exarchates of North Africa or Ravenna. As it had been in the West, so it now was in the East. Civil problems were inseparable from the military: Heraclius could not hope to dispense justice, collect taxes, protect the church, and ensure the future to his dynasty unless military power reinforced his orders. A system of military government, the exarchate, had accomplished those objectives so well in the West that, in a moment of despair, Heraclius sought to return to the land of his origins. In all likelihood, he applied similar principles of military rule to his possessions throughout Asia Minor, granting his generals (stratēgoi) both civil and military authority over those lands that they occupied with their “themes,” as the army groups, or corps, were called in the first years of the 7th century.

Second, during the social upheaval of the previous decade, the imperial treasury had doubtless seized the estates of prominent individuals who had been executed either during Phocas’s reign of terror or after his death. In consequence, though the treasury lacked money, it nonetheless possessed land in abundance, and Heraclius could easily have supported with grants of land those cavalry soldiers whose expenses in horses and armament he could not hope to meet with cash. If that hypothesis is correct, then, even before 622, themes, or army groups—including the guards (Opsikioi), the Armenians (Armeniakoi), and the Easterners (Anatolikoi)—were given lands and settled throughout Asia Minor in so permanent a fashion that, before the century was out, the lands occupied by those themes were identified by the names of those who occupied them. The Opsikioi were to be found in the Opsikion theme, the Armeniakoi in the Armeniakon, and the Anatolikoi in the Anatolikon. The term theme ceased thereafter to identify an army group and described instead the medieval Byzantine unit of local administration, the theme under the authority of the themal commander, the general (stratēgos).

When Heraclius “went out into the lands of the themes” in 622, thereby undertaking a struggle of seven years’ duration against the Persians, he utilized the third of his sources of strength: religion. The warfare that ensued was nothing less than a holy war: it was partly financed by the treasure placed by the church at the disposal of the state; the emperor’s soldiers called upon God to aid them as they charged into battle; and they took comfort in the miraculous image of Christ that preceded them in their line of march. A brief summary of the campaign unfortunately gives no idea of the difficulties Heraclius encountered as he liberated Asia Minor (622), fought in Armenia with allies found among the Christian Caucasian peoples, the Lazi, the Abasgi, and the Iberians (624), and struggled in far-distant Lazica while Constantinople withstood a combined siege of Avars and Persians (626). An alliance with the Khazars, a Turkic people from north of the Caucasus, proved of material assistance in those years and of lasting import in Byzantine diplomacy. Heraclius finally destroyed the main Persian host at Nineveh in 627 and, after occupying Dastagird in 628, savoured the full flavour of triumph when his enemy, Khosrow, was deposed and murdered. The Byzantine emperor might well have believed that, if the earlier success of the Persians signalized the resurrection of the Achaemenid empire, his own successes had realized the dreams of Caesar, Augustus, and Trajan.

Yet that was a war fought by medieval Byzantium and not by ancient Rome. Its spirit was manifest in 630, when Heraclius triumphantly restored the True Cross to Jerusalem, whence the Persians had stolen it, and—even more—when Constantinople resisted the Avar-Persian assault of 626. During the attack, the patriarch Sergius maintained the morale of the valiant garrison by proceeding about the walls, bearing the image of Christ to ward off fire, and by painting upon the gates of the western walls images of the Virgin and child to ward off attacks launched by the Avars—the “breed of darkness.” The Avars withdrew when Byzantine ships defeated the canoes manned by Slavs, upon whom the nomad Avars depended for their naval strength. The latter never recovered from their defeat. As their empire crumbled, new peoples from the Black Sea to the Balkans emerged to seize power: the Bulgars of Kuvrat, the Slavs under Samo, and the Serbs and Croats whom Heraclius permitted to settle in the northwest Balkans once they had accepted Christianity.

As for the Byzantine defenders of Constantinople, they celebrated their victory by singing Romanos’s great hymn “Akathistos,” with choir and crowd alternating in the chant of the “Alleluia.” The hymn, still sung in a Lenten service, commemorates those days when Constantinople survived as a fortress under ecclesiastical leadership, its defenders protected by the icons and united by their liturgy. This they sang in Greek, as befitted a people whose culture was now Greek and no longer Latin.

The successors of Heraclius: Islam and the Bulgars

In the same year that Heraclius went out into the themes, Muhammad made his withdrawal (hijrah) from Mecca to Medina, where he established the ummah, or Muslim community. Upon the Prophet’s death in 632, the caliphs, or successors, channeled the energies of the Arab Bedouin by launching them upon a purposive and organized plan of conquest. The results were spectacular: a Byzantine army was defeated at the Battle of the Yarmūk River (636), thereby opening Palestine and Syria to Arab Muslim control. Alexandria capitulated in 642, removing forever the province of Egypt from Byzantine authority. The Arabs had, meanwhile, advanced into Mesopotamia, capturing the royal city of Ctesiphon and, eventually, defeating an army under command of the Persian king himself. So ended the long history of Persia under Achaemenids, Parthians, and Sāsānians; further conquests were shortly to initiate that region’s Islamic phase (see Iran, history of: Iran from 640 to the present; Islamic world).

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.

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.

So it was too in trade and commerce. After the loss of Egypt and North Africa, the grain fleets manned by hereditary shipmasters disappeared. In their place there emerged the independent merchant, of sufficient importance to call forth a code of customary law, the Rhodian Sea Law, to regulate his practices. Military and religious hostilities failed to check him as he traded with the Bulgars in Thrace and, through Cyprus, with the Arabs. Despite constant warfare, this was, in short, a healthier society than the late Roman, and its chances of survival were further increased when the sixth general council (680–681) condemned Monothelitism and anathematized its adherents. With Egypt and Syria under Muslim rule, it was no longer necessary to placate Eastern Monophysitism, and it seemed that doctrinal discord would no longer separate Constantinople from the West. Events were to prove otherwise.