Byzantium is an elusive phenomenon because so many of its constituent parts altered in place and over time. The overarching fac¸ade of the imperial order remained, with certain fixed points: religious doctrine, use of the Greek language, and the City of Constantinople itself. But many other elements were mutable – from court fashions, administrative methods and commercial undertakings, to forms of warfare or territorial possessions. Byzantium’s distinctive qualities lie in this interplay between the fixed and the changeable, the expendable and the non-negotiable, ensuring its endurance across a millennium or so, longevity which only the Chinese and Japanese empires can unequivocally be said to have surpassed. However, even the chronological limits of the Byzantine empire are contentious. In a material sense, the Constantinopolitan-based emperor could be regarded as powerless, politically dead by the time Sultan Mehmed II’s technicians closed the Bosporus and trained their guns on the City in 1453. Yet alternative or affiliated imperial regimes were still functioning, and to all appearances the empire of Trebizond and the despotate of the Morea could have carried on indefinitely, even flourished, had the Ottomans not determined to put paid to them, too, while reducing other robust polities in the Balkans to tributary status (see below, pp. 831–2, 860–1). And the idea of the central place of the empire and the City in God’s scheme of things persisted among the orthodox well after 1453. From that point of view, 1492 – when the world had been predicted to end following upon the empire’s fall (see above, p. 7) – seems as good a date as any to conclude. And it is not wholly coincidental that 1492 saw the discovery of the New World: Christopher Columbus, himself of Genoese stock, was sailing a refined version of the type of cog which plied directly between Genoese Chios, England and Flanders until the Turks began putting pressure on their trading activities in the Levant (see below, pp. 847–8). Our story might accordingly begin with the new covenant between God and mankind which Constantine the Great (306–37) made upon accepting the Christian religion and basing himself in the city of Byzantion. That is when the emperor became a figure of universal value to influential Christian churchmen such as Eusebius (see above, p. 6). Triumphalist notions about the Christian empire’s destiny and hopes of individual spiritual rebirth started to filter through the lettered and propertied classes of the RomanMediterranean and other strata of society, providing a sense of purpose and consolation through military setbacks and periodic devastation. In other words, something of the amalgam of Christian faith and eschatological hopes that characterised medieval Byzantium was already being mixed in the fourth century, when the Roman empire encompassed much of continental Europe, was a formidable presence in Africa and western Asia and still harboured notions of conquering Persia. To begin the story with Constantine among his bishops has all the more to recommend it, in that the Christian empire’s longevity and perseverance through a variety of changes of fortune and circumstances is the connecting theme of this book. Besides, Constantine’s conversion is roughly the point where several other authoritative surveys of Byzantium begin, whether focused on the ups and downs of the Byzantine state and its ruling classes;1 on the thought-world of the faithful and the dissenters of Byzantium;2 or dealing with culture and society as well as matters of state.3 However, both practical and theoretical considerations have discouraged us from beginning with the fourth century. Constantine accepted Christianity in 312 but the processes by which Christian observance became irreversible, an indispensable attribute of Romanness, were intricate and protracted. At the time of Constantine’s death in 337 and for many decades to come, the majority of the population were non-Christian. The diffusion of Christianity can partly, but only partly, be charted through the injunctions of senior churchmen, the edicts of emperors and the feats of holy men. The decisions of individuals, families or communities to adopt the Christian faith and forms of worship could be made for many different reasons, not least peer-group pressure. These processes are seldom set out in reliable detail in our surviving sources, and such records as there are come from highly partisan writers.4 The fifth century saw the construction of important platforms and spectacular pinnacles of Christian empire that would be admired and utilised by much later regimes in the Christian west as well as the east. The ‘rhetoric of empire’, already well worked upon by Eusebius, Themistius, John Chrysostom and others in the fourth century, was further elaborated.5 A vibrant court culture and ceremonial accrued around the figure of the emperor ensconced in his ‘sacred palace’, the majesty and dignitaries of his court evoking the heavenly court above.6 The monuments of this architecture of empire took both material and institutional form, from the walls of Constantinople, built for Theodosius II (402–50) (fig. 2), to the almost as massive law-code, the Codex Theodosianus, that he promulgated. This law-code marks a milestone in emperors’ attempts to codify law and governance across the spectrum of society, providing for church property and the jurisdiction of bishops and the religious observances and way of life of ordinary subjects. An entire book of the Codex is devoted to religious issues, heretics, Jews and pagans among them.7 These new materials of empire-building did not, however, make unreservedly for the consolidation of imperial power. The leadership of the church was prone to bitter disagreements over elements of doctrine such as the interrelationship of the divine and human qualities of Christ. These controversies periodically reached boiling-point and assemblies of patriarchs and bishops were convened under the supervision of emperors to try and reach an agreement. Of these ‘universal’ – ecumenical – councils, the council of Chalcedon (451) stands out as of particular importance. Its outcome was a formula concerning Christ: that He was ‘recognised in two natures’ while also ‘in one person and hypostasis’. This was acceptable to the papacy, being very close to the terms which it had formulated, and EmperorMarcian’s commissioners pressed the council to accept it. Serious fault-lines, however, remained both among eastern churchmen and between easterners and the papacy.8 The divisions would reopen and become still more acrimonious in the following century. A case could be made for bringing these achievements and controversies within the compass of this book, treating ‘the Byzantine empire’ as already in place in the fifth century. However, such identification of the empire’s development and well-being with the formal elaboration of Christian doctrine by councils and the spread of Christian observance in everyday life raises three major difficulties. Firstly, as already stated, Christianity spread along multifarious channels and its effects – or otherwise – on social attitudes and behaviour patterns in town and country varied greatly between communities and regions. The onset of the new religion in its various guises has been much discussed in recent English-speaking scholarship and might seem to provide grounds for studying the Christianising empire of the fifth and sixth centuries en bloc. But scholarly voices have also sounded in favour of closer attention to the nuts and bolts of empire, institutions of governance such as the law and its enforcement, the state apparatus for revenue raising and expenditure, and coinage.9 These institutions remained in working order across much of the eastern empire throughout the fifth century, and the continuing pax romana rested on impressive reserves of military manpower, coordinated to awesome effect. So long as the empire presented obvious and overwhelming advantages of martial strength, prosperity and public welfare, these material benefits spoke for themselves. Christian preachers and holy men might inveigh against alternative cults, indifference, materialism and – in matters of discipline and doctrine – against one another, and their written outpourings have survived in bulk, as has the Christian framing which orators and senior churchmen now provided for imperial power. But while that power still appeared to underwrite general well-being out of its own vast resources, in the heterogeneous and multi-cult towns and settlements of the easternMediterranean region,10 Christian worship and observance had a wide range of alternative connotations for their inhabitants – whether as an optional extra supplementing other devotions; an imposition; a familial or communal tradition of cult practices and obligations; or an avenue for individual spiritual development. Christian court culture and splendiferous trappings supplemented, embellished and enhanced imperial power, rather than virtually substituting for it. Faith and worship were a valued asset in bringing the emperor victories and the empire dominance, but they were not yet generally seen as vital to the empire’s survival: the empire did not yet, in the fifth century, amount to a faithzone. 11 Secondly, many shades of Christian belief, practices and organisation were developing under their own momentum, on a geographical scale extending far beyond the empire’s frontiers. The ferment of Christianity in the fertile crescent and other parts of the orient posed obstacles for the Roman emperor as well as openings. When Armenia’s King Tiridates IV adopted Christianity early in the fourth century, the Armenian church organisation and distinctive Armenian script provided buildingblocks for the development of a separate political identity. Yet occasionally prospects opened up of bringing Armenia – ever a region of keen strategic interest – under Roman hegemony, if only Armenian churchmen would subscribe to imperially approved church doctrine (see below, pp. 169–70, 337–8). Persia is another example of how Christianity was something of a double-edged sword for the Roman empire. The Sasanians offered safe haven for dissidents, vociferously at odds with the established church and (often) with the imperial authorities; by the sixth century the Nestorians made up a substantial portion of the Persian population and Persianoccupied Nisibis was a school for dissenters from the imperial line. Yet there flickered the prospect of further Christian converts in Sasanian ruling circles and it was not inconceivable that key individuals might opt for Chalcedonian orthodoxy (see below, pp. 136, 142–4, 311). Meanwhile, and less spectacularly, ruling families and local communities adopted Christianity in the Arabian peninsula, Abyssinia and the Sudan for a variety of reasons, sometimes thanks to proselytisation by sects which operated in rivalry with missionaries sponsored by the emperor (see below, pp. 180, 188–9, 308–11). These movements and cross-currents among other societies and powers posed anomalies and challenges to an empire purporting to embody Christianity on earth. It has therefore seemed appropriate to include chapters which look back in detail to the more important developments on the empire’s eastern approaches around the time of Constantine’s conversion.12 They put in perspective the church councils of Ephesus (431) and Chalcedon and those of the sixth century,13 and also the tug of culturoreligious forces working on imperial decision-making from east and west. However, a balanced presentation of the fifth century for its own sake would require full coverage of the western half of the empire, too, and this constitutes a third reason why overall treatment of the fifth-century empire is not attempted here. Law and order ceased to be the sole preserve of the imperial authorities in the west long before the abdication of the last legitimate emperor, Romulus Augustulus, in 476. In the west, the adoption of Christianity as the official religion of the empire appeared to usher in political turbulence and disorder, rather than consolidating military effectiveness, state-maintained infrastructure and prosperity, as it did in the east. Furthermore issues such as the diffusion of power; the levels of law and order sustained and of everyday violence; and the calibre of urban living and economic activity in the Mediterranean world and the Roman provinces further north are highly contentious.14 The contrasts and cross-currents between the easternMediterranean world and the Christian west are a key theme of this work, but the dissolution of empire in the west has distinctive, often quite local, explanations. The broader implications for the eastern empire of the formation of more or less ‘barbarian’ regimes in the central and western Mediterranean regions will be discussed below (see ch. 3). That their existence was unprecedented, posing new problems yet also diplomatic and strategic openings for the rulers of Constantinople, is hard to deny, and this goes some way towards justifying the starting-point of this book around ad 500.15 We have therefore begun our story around the time when Byzantium first stood alone as a working Christian empire, surrounded by potentially formidable predators. Those seeking balanced treatment of the economic, social and politico-administrative history of the earliest centuries of the ChristianisingRoman empire have only to turn to the three final volumes of the Cambridge ancient history, which have advanced the bounds of classical antiquity up to around ad 600.16 They will also find the progress of the Christian faith and its practices traced from its beginnings, across the length and breadth of the Roman empire and beyond, in the Cambridge history of Christianity. The first volume includes accounts of Constantine’s reign and the first council of Nicaea.17 Also of use are discussions by individual scholars or teams of conference speakers on the problems of the sense in which late antiquity may be said to have ended and the Byzantine empire begun, of how far the sixth century marks an end or a beginning.