The picture in the East is more complex. We’ve been avoiding the Eastern Roman Empire because our question is about the fall of Rome and Rome didn’t fall there. Like the successor states of the western Roman Empire, the Eastern Roman Empire was heir to the centralized, bureaucratic, somewhat top-heavy imperial system of the late empire, though whereas the western Empire had multiple centers of power (Rome itself, but also Ravenna, Milan, and Split all spent time as imperial headquarters), in the East, Constantinople was the obvious center of the empire and thus the home of the imperial bureaucracy.

This isn’t a place for a full history of the Eastern Roman Empire (because that would run until 1453), but we do need to note some features. The Eastern Roman Empire was more urbanized, more densely peopled and wealthier than the west, but it also faced arguably more severe security problems in the fifth century and beyond. The east was as exposed in the fifth century to the in-migration of the Goths (Adrianople had been in the Eastern Empire, after all) and later the Huns, but the armies of the east always had to have their primary focus on the eastern border with the Sassanid Empire. Founded out of the collapse of the Parthian Empire in 205, the Sassanid Empire was a hostile competitor to Rome for its entire existence (205-651), with the two at war more often than not and engaged in a robust cold war stand off between wars. The Sassanids, controlling the Iranian Plateau, Mesopotamia and the coastlines of the Persian Gulf, were a true peer to the Eastern Roman Empire, similar in size, population and wealth. Both states had sophisticated and disciplined armies.

The fourth century had seen a series of major wars between the two powers, culminating in the disastrous campaign of 363 which cost the emperor Julian his life. Despite more minor flare-ups (in 421 and 440), the fifth century was calmer which was fortunate because the Eastern Roman Empire had its hands full for much of the century dealing with the Goths and Huns. But the calm broke in the sixth century with a series of inconclusive but escalating wars (502-506, 526-532, 541-562, 572-591). Nevertheless it was in the midst of this that the emperor Justinian (r. 527-565) – an emperor of considerable talents and supported by the equally talented Empress Theodora – felt strong enough to try to reclaim large parts of the Western Roman Empire, launching invasions into North Africa, Italy and Spain while also fighting with the Sassanids. Justinian’s campaigns were successful, but they mostly succeed only in straining imperial resources, especially because climate-motivated harvest failures in the 530s and plague in the 540s severely weakened the empire precisely as he was stretching it.

The bigger catastrophe was Khosrow II (r. 590-628), a Sassanid Shahanshah with both talents and ambitions to match the by then deceased Justinian, who would be even more of a disaster to his own empire. In 602, Khosrow launched what would be the last great Roman-Sassanid War (though by this point, after Justinian, we generally call this state the Byzantine Empire, so this would be the last great Byzantine-Sassanid War; I am going to keep calling these folks the Romans because that’s what they called themselves). Khosrow was initially fantastically successful, overrunning much of the Eastern Roman Empire and even laying siege to Constantinople in 626 but then the tide turned catastrophically against him. Khosrow II was killed in a mutiny which sparked civil war in the Sassanid Empire and left both empires exhausted, their subjects over-taxed and war weary. And then in 634, Arab armies, united by the new religion of Islam slammed into the Roman province of Syria; by 650, Egypt, Syria and the Levant were lost to the Romans, while the Sassanid Empire was destroyed outright. What was left of the Eastern Roman Empire became a primarily Aegean power, its strength concentrated in the Balkan Peninsula and Anatolia and the sea that united them.

Unlike in the West, where the Church and secular rulership had eventually become separate institutions, in the East the emperor and the church – what would become the Eastern Orthodox Church – were closely linked and there was an expectation that the emperor would encourage the “right” sort of Christianity. That was certainly a continuity with early Roman policy – the first emperor to persecute Christians for being the “wrong sort” of Christians was Constantine who persecuted the Donatists. By 388, imperial law required all citizens of the empire to follow “catholic” Christianity (the term adopted, amusingly, by the anti-Donatists to define themselves against the Donatist “heretics”; in this context it doesn’t mean “Roman Catholic” but merely “not heretical”) and so the emperors attempted to enforce that. This was a problem because prior to the loss of Syria and Egypt to the Rashidun Caliphate, the “heretics” may have outnumbered the “orthodox” though of course the many splintered heretical branches didn’t agree with each other either. Miaphysite Christianity was common in Egypt and the Levant and Nestorianism was common in Syria (though many Nestorians fled Roman persecution to live in the Sassanid Empire). Efforts by the imperial center to stamp out these branches of Christianity contributed to the ease with which the southern parts of the empire were lost to the Rashidun Caliphate: many “heretical” Christians could expect better treatment under Muslim rulers who did not much care what sort of Christian one was.

Urban culture lasted longer in the east than in the west, though regional patterns vary. In Syria, Egypt and the Levant, Liebescheutz notes that on the whole the classical form of city continues largely unchanged during the fifth century and indeed continues relatively undiminished until the eighth century. The relatively rapid Muslim conquests caused these regions to transition fairly seamlessly from being protected Roman territory to being the core heartland of the Umayyad dynasty; it was only the movement of the capital to Baghdad under the Abbasid which finally led to the marked decline of these civic centers. The exception here were cities that had thrived off of Mediterranean trade – places like Antioch, Tyre and Caesarea, which lost importance as those trade systems broke down, though their fall was matched by the rise of places like Aleppo, Damascus, and Emesa (modern Homs).

Urban decline in Anatolia and around the Aegean was swifter and sharper; older scholarship (and occasionally newer scholarship) tends to assume that the downturn for most of these cities began with the catastrophic Roman-Sassanid Wars of the 600s, but Liebescheutz shows fairly clearly that for the smaller centers, the decline set in substantially earlier, though the full collapse would come only in the seventh century. What seems to be the main factor was the further centralization of Roman administration, leading to wealth and importance piling up around regional and provincial capitals which became the focus of that centralized administration. Consequently the smaller centers declined sharply, while the provincial and later theme capitals held on.

Roman governance in the east responded to the challenges of the sixth and seventh century with evolution. Civil and military officials, who had been divided by Diocletian, began to be merged back together by Justinian in an effort to make provinces which were more able to defend themselves; this trend would continue and culminate in the mid-seventh century with the theme system, which tied territorial division directly to local military units (both called themata) which in theory were then supported by the main field army (the tagmata) which stayed with the emperor in Constantinople. This system shed almost all of its old Roman terminology and organization (indeed, much of it was gone by the age of Justinian), but it represented a fairly straightforward evolution of the Late Roman army, changing in small evolutionary steps over centuries.

If our look at “Words” was largely a victory for our knight of “change and continuity”, the look at “Institutions” has been much more mixed, with the collapse of urbanism in particular making for a strong argument for a “decline and fall” viewpoint. But the collapse of institutions was hardly a complete process, with significant survivals in the Church and also in the east. And while political institutions did collapse, the kingdoms that followed owed more than a little of their structure to the Roman model that had come before, yet at the same time, the decline of administrative capacity and state capabilities is obvious: these were smaller, weaker, poorer states. In my own view, the question, in the end, really comes down to the impact this period had on the lives of the great majority of people who were not elites and did not wield any power within the great institutions of the day.

Bret Devereaux, “Collections: Rome: Decline and Fall? Part II: Institutions”, A Collection of Unmitigated Pedantry, 2022-01-28.