Roman Decline

The Decline of the Roman Empire, leading to the Fall of the Roman Empire, or the Fall of Rome, was the end of the Western Roman Empire. Edward Gibbon, in his famous study The Decline and Fall of the Roman Empire (1776), was the first to use this terminology after Montesquieu, but he was neither the first nor the last to speculate on why and when the Empire collapsed. "From the eighteenth century onward," Glen W. Bowersock has remarked,[1] "we have been obsessed with the fall: it has been valued as an archetype for every perceived decline, and, hence, as a symbol for our own fears." It remains one of the greatest historical questions, and has a tradition rich in scholarly interest. In 1984, German professor Alexander Demandt published a collection of 210 theories on why Rome fell, and a number of new theories have emerged since then.[2]

The traditional date of the fall of the Roman Empire is September 4, 476 when Romulus Augustulus, the last Emperor of the Western Roman Empire was deposed by Odoacer. Julius Nepos, the legitimate emperor recognized by the East Roman Empire continued to live in Salona, Dalmatia until he was assassinated in 480. Some modern historians question the relevance of this date,[3] as the Ostrogoths who succeeded considered themselves as upholders of the direct line of Roman traditions, and noting, as Gibbon did, that the Eastern Roman Empire was going from strength to strength and continued until the Fall of Constantinople on May 29, 1453. Some other notable dates are the Battle of Adrianople in 378, the death of Theodosius I in 395 (the last time the Roman Empire was politically unified), the crossing of the Rhine in 406 by Germanic tribes after the withdrawal of the troops in order to defend Italy against Alaric I (such invasions had occurred many times previously but this time it was successful), the death of Stilicho in 408, followed by the disintegration of the western army, the Sack of Rome (410), the first time in almost 800 years that the city of Rome had fallen to a foreign enemy, the death of Justinian I, the last Roman Emperor who tried to reconquer the west, in 565, and the coming of Islam after 632. Many scholars maintain that rather than a "fall", the changes can more accurately be described as a complex transformation.[4] Over time many theories have been proposed on why the Empire fell, or whether indeed it fell at all.

The decline of the Roman Empire is one of the events traditionally marking the end of Classical Antiquity and the start of the European Middle Ages. Throughout the fifth century, the Empire's territories in western Europe and northwestern Africa, including Italy, fell to various invading or indigenous peoples in what is sometimes called the Migration period. Although the eastern half still survived with borders essentially intact for several centuries (until the Arab expansion), the Empire as a whole had initiated major cultural and political transformations since the Crisis of the Third Century, with the shift towards a more openly autocratic and ritualized form of government, the adoption of Christianity as the state religion, and a general rejection of the Classical Antiquities traditions and values. While traditional historiography emphasized this break with Antiquity by using the term "Byzantine Empire" instead of Roman Empire, recent schools of history offer a more nuanced view, seeing mostly continuity rather than a sharp break. The Empire of Late Antiquity already looked very different from classical Rome.

The Roman Empire emerged from the Roman Republic when Julius Caesar and Augustus Caesar transformed it from a republic into a monarchy. Rome reached its zenith in the second century, then fortunes slowly decline (with many revivals and restorations along the way). The reasons for the decline of the Empire are still debated today, and likely multiple. Historians infer that the population appears to have diminished in many provinces--especially western Europe--from the diminishing size of fortifications built to protect the cities from barbarian incursions from the 3rd century on. Because these fortifications were restricted to the center of the city only, some have suggested that parts of the periphery were not inhabited anymore.

By the late third century, the city of Rome no longer served as an effective capital for the Emperor and various cities were used as new administrative capitals. Successive emperors, starting with Constantine, privileged the eastern city of Byzantium, which he had entirely rebuilt after a siege. Later renamed Constantinople, and protected by formidable walls in the late fourth and early fifth centuries, it was to become the largest and most powerful city of Christian Europe in the Early Middle Ages. Since the Crisis of the Third Century, the Empire was intermittently ruled by more than one emperor at once (usually two), presiding over different regions. At first a haphazard form of power sharing, this eventually settled on an East-West administrative division between the Western Roman Empire (centered on Rome, but now usually presided from other seats of power such as Trier, Milan, and especially Ravenna), and the Eastern Roman Empire (with its capital initially in Nicomedia, and later Constantinople). The Latin-speaking west, under severe demographic crisis, and the wealthier Greek-speaking east, also began to diverge politically and culturally. Although this was a gradual process, still incomplete when Italy came under the rule of Barbarian chieftains in the last quarter of the 5th century, it deepened further afterwards, and had lasting consequences for the medieval history of Europe.

Throughout the fifth century, western emperors were usually figureheads, while in the eastern emperors managed to secure their independence from influential military leaders. For most of the time, the actual rulers in the West were military strongmen who took the titles of magister militum, patrician, or both, such as Stilicho and Aetius. Although Rome was no longer the capital in the West it remained the West's largest city and its economic center. But the city was sacked by rebelled Visigoths in 410 (for three days) and later again by the Vandals in 455 (for fourteen days), events that shocked the contemporaries and signalled the disintegration of Roman authority. Saint Augustine wrote The City of God partly as an answer to critics who blamed the sack of Rome by the Visigoths on the abandonment of the traditional pagan religions.

In June 474, Julius Nepos became Western Emperor but in the next year the magister militum Orestes revolted and made his son Romulus Augustus emperor. Romulus, however, was not recognized by the Eastern Emperor Zeno and so was technically an usurper, Nepos still being the legal Western Emperor. Nevertheless, Romulus Augustus is often known as the last Western Roman Emperor. In 476 after being refused lands in Italy, Orestes' Germanic mercenaries, led by the chieftain Odoacer, captured and executed Orestes and took Ravenna, the Western Roman capital at the time, deposing Romulus Augustus. The whole of Italy was quickly conquered and Odoacer was granted the title of patrician by Zeno effectively recognizing his rule in the name of the Eastern Empire. Since, as a barbarian, he was not allowed the title of Emperor,[citation needed] Odoacer returned the Imperial insignia to Constantinople and ruled as King in Italy. Following Nepos' death Theodoric the Great, King of the Ostrogoths, conquered Italy with Zeno's approval.

The East Roman Empire and Barbaric Kingdoms in 480Meanwhile, much of the rest of the Western provinces were conquered by waves of Germanic invasions, most of them being disconnected politically from the East altogether and continuing a slow decline. Although central authority in the West had been lost, Roman culture would continue to exist in most of parts of the former Western provinces into the sixth century and beyond.

The first invasions had disrupted the West to some degree, but it was the Gothic War launched by the Eastern Emperor Justinian in the sixth century, and meant to reunite the Empire, that eventually caused the most damage to Italy, as well as straining the Eastern Empire militarily. Following these wars Rome and other Italian cities would fall into severe decline (Rome itself was almost completely abandoned). A last blow came with the Persian invasion of the East in the seventh century, immediately followed by the Muslim conquests, especially of Egypt, which curtailed much of the key trade in the Mediterranean on which Europe depended.

The Empire was to live on in the east for many centuries, and enjoy periods of recovery and cultural brilliance, but its size would remain a fraction of what it had been in classical times. It became an essentially regional power, centered on Greece and Anatolia. Modern historians tend to prefer the term Byzantine Empire for the eastern, medieval stage of the Roman Empire.

Highlights The decline of the Roman Empire was a gradual transformation that cannot be dated precisely. Some stepping stones in the path toward the loss of the western part of the Empire, the weakening of its eastern part, and the progressive estrangement between the two halves, are nevertheless worth remarking:

3rd century The Crisis of the Third Century (234 - 284), a period of political anarchy. The reign of emperor Diocletian (284 - 305), who attempted substantial political and economic reforms, many of which would remain in force in the following centuries. 4th century The reign of Constantine I (306 - 337), who built the new eastern capital of Constantinople, and converted to Christianity, legalizing and even favoring to some extent this religion. All Roman emperors after Constantine, with the exception of Julian, would be Christians. The first war with the Visigoths (376 - 382), culminating in the Battle of Adrianople (August 9, 378), in which a large Roman army was defeated by the Visigoths, and emperor Valens was killed. The Visigoths, fleeing a migration of the Huns, had been allowed to settle within the borders of the Empire by Valens, but were mistreated by the local Roman administrators, and rebelled. The reign of Theodosius I (379 - 395), last emperor to reunite under his authority the western and eastern halves of the Empire. Theodosius continued and intensified the policies against paganism of his predecessors, eventually outlawing it, and making Nicaean Christianity the state religion. 5th century The Crossing of the Rhine: on December 31, 406 (or 405, according to some historians), a mixed band of Vandals, Suebi and Alans crossed the frozen river Rhine at Moguntiacum (modern Mainz), and began to ravage Gaul. Some moved on to the regions of Hispania and Africa. The Empire would never regain control over most of these lands. The second war with the Visigoths, led by king Alaric, in which they raided Greece, and then invaded Italy, culminating in the sack of Rome (410). The Visigoths eventually left Italy, and founded the Visigothic Kingdom in southern Gaul and Hispania. The rise of the Hunnic Empire under Attila and Bleda (434-453), who raided the Balkans, Gaul, and Italy, threatening both Constantinople and Rome. The second sack of Rome, by the Vandals (455). Failed counterstrikes against the Vandals (461 - 468). The western emperor Majorian planned a naval campaign against the Vandals to reconquer northern Africa in 461, but word of the preparations got out to the Vandals, who took the Roman fleet by surprise and destroyed it. A second naval expedition against the Vandals, sent by emperors Leo I and Anthemius, was defeated in 468. Deposition of the last western emperors, Julius Nepos and Romulus Augustus (475 - 480). Julius Nepos, who had been nominated by the eastern emperor Zeno, was deposed by the rebelled magister militum Orestes, who installed his own son Romulus in the imperial throne. Both Zeno and his rival Basiliscus, in the East, continued to regard Julius Nepos, who fled to Dalmatia, as the legitimate western emperor, and Romulus as an usurper. Shortly after, Odoacer, magister militum appointed by Julius, invaded Italy, defeated Orestes and deposed the child emperor Romulus Augustus on September 4, 476. He then proclaimed himself ruler of Italy and asked the eastern emperor Zeno to become formal emperor of the entire empire, and in so doing legalize Odoacer's own position as imperial viceroy of Italy. Zeno did so, setting aside the claims of Nepos, who was murdered by his own soldiers in 480. Foundation of the Ostrogothic Kingdom in Italy (493). Concerned with the success and popularity of Odoacer, Zeno started a campaign against him, at first with words, then by inciting the Ostrogoths to take back Italy from him. They did as much, but then founded an independent kingdom of their own, under the rule of king Theodoric. Italy and the entire West were lost to the Empire.

Explaining the fall of the Empire

Vegetius The historian Vegetius theorized, and has recently been supported by the historian Arthur Ferrill, that the Roman Empire – particularly the military – declined partially as a result of an influx of Germanic mercenaries into the ranks of the legions. This "Germanization" and the resultant cultural dilution or "barbarization", led to lethargy, complacency and loyalty to the Roman commanders, instead of the Roman government, among the legions and a surge in decadence amongst Roman citizenry.

Edward Gibbon Edward Gibbon famously placed the blame on a loss of civic virtue among the Roman citizens. They gradually entrusted the role of defending the Empire to barbarian mercenaries who eventually turned on them. Gibbon considered that Christianity had contributed to this, making the populace less interested in the worldly here-and-now and more willing to wait for the rewards of heaven. "The decline of Rome was the natural and inevitable effect of immoderate greatness. Prosperity ripened the principle of decay; the causes of destruction multiplied with the extent of conquest; and as soon as time or accident had removed the artificial supports, the stupendous fabric yielded to the pressure of its own weight," he wrote. "In discussing Barbarism and Christianity I have actually been discussing the Fall of Rome."

Henri Pirenne In the second half of the 19th century some historians focused on continuing events in the Roman world and the post-Roman Germanic kingdoms. Fustel de Coulanges in Histoire des institutions politiques de l'ancienne France (1875–1889) argued that the barbarians simply contributed to a running process in their role of transforming Roman institutions.

Henri Pirenne continued this idea in "Pirenne Thesis", published in the 1920s, which remains influential to this day. It holds that the Empire continued, in some form, up until the time of the Muslim conquests in the 7th century, which disrupted Mediterranean trade routes, leading to a decline in the European economy. This theory stipulates the rise of the Frankish realm in Europe as a continuation of the Roman Empire, and thus legitimizes the crowning of Charlemagne as the first Holy Roman Emperor as a continuation of the Imperial Roman state.

Pirenne's view on the continuity of the Roman Empire before and after the Germanic invasion was supported by recent historians such as François Masai, Karl-Ferdinand Werner and Peter Brown.

However, some critics maintain the "Pirenne Thesis" erred in claiming the Carolingian realm as a Roman state, and mainly dealt with the Islamic conquests and their effect on the Byzantine or Eastern Empire.

Other modern critics stipulate that while Pirenne is correct in his assertion of the continuation of the Empire beyond the sack of Rome, the Arab conquests in the 7th century may not have disrupted Mediterranean trade routes to the degree that Pirenne suggests. Michael McCormick in particular notes that more recent sources, such as unearthed collective biographies, notate new trade routes through correspondences in communication. Moreover, records such as book-keepings and coins suggest the movement of Islamic currency into the Carolingian Empire. McCormick concludes that if money is coming in, some form of trade is going out – including slaves, timber, weapons, honey, amber, and furs.

J. B. Bury John Bagnell Bury's History of the Later Roman Empire gives a multi-factored theory for the Fall of the Western Empire. He presents the classic "Christianity vs. pagan" theory, and dismisses it, citing the relative success of the Eastern Empire, which was far more Christian.

He then examines Gibbon's "theory of moral decay," and without insulting Gibbon, finds that to be too simplistic, though a partial answer. He essentially presents what he called the "modern" theory, which he implicitly endorses, a combination of factors, primarily, (quoting directly from Bury):[5]

… The Empire had come to depend on the enrollment of barbarians, in large numbers, in the army, and … it was necessary to render the service attractive to them by the prospect of power and wealth. This was, of course, a consequence of the decline in military spirit, and of depopulation, in the old civilised Mediterranean countries. The Germans in high command had been useful, but the dangers involved in the policy had been shown in the cases of Merobaudes and Arbogastes. Yet this policy need not have led to the dismemberment of the Empire, and but for that series of chances its western provinces would not have been converted, as and when they were, into German kingdoms. It may be said that a German penetration of western Europe must ultimately have come about. But even if that were certain, it might have happened in another way, at a later time, more gradually, and with less violence. The point of the present contention is that Rome's loss of her provinces in the fifth century was not an "inevitable effect of any of those features which have been rightly or wrongly described as causes or consequences of her general 'decline.'" The central fact that Rome could not dispense with the help of barbarians for her wars (gentium barbararum auxilio indigemus) may be held to be the cause of her calamities, but it was a weakness which might have continued to be far short of fatal but for the sequence of contingencies pointed out above.[5]

In short, Bury held that a number of contingencies arose simultaneously: economic decline, Germanic expansion, depopulation of Italy, dependency on Germanic foederati for the military, the disastrous (though Bury believed unknowing) treason of Stilicho, loss of martial vigor, Aetius' murder, the lack of any leader to replace Aetius — a series of misfortunes which proved catastrophic in combination.

Bury noted that Gibbon's "Decline and Fall of the Roman Empire" was "amazing" in its research and detail. Bury's main differences from Gibbon lay in his interpretation of fact, rather than any dispute of fact. He made clear that he felt that Gibbon's conclusions as to the "moral decay" were viable — but not complete. Bury's judgement was that:

The gradual collapse of the Roman power …was the consequence of a series of contingent events. No general causes can be assigned that made it inevitable.

It is his theory that the decline and ultimate fall of Rome was not pre-ordained, but was brought on by contingent events, each of them separately endurable, but together and in conjunction ultimately destructive.

Radovan Richta On the other hand, some historians have argued that the collapse of Rome was outside the Romans' control. Radovan Richta holds that technology drives history. Thus, the invention of the horseshoe in Germania in the 200s would alter the military equation of pax romana.

Lucien Musset and the clash of civilizations In the spirit of "Pirenne thesis", a school of thought pictured a clash of civilizations between the Roman and the Germanic world, a process taking place roughly between 3rd and 8th century.

The French historian Lucien Musset, studying the Barbarian invasions, argues the civilization of Medieval Europe emerged from a synthesis between the Graeco-Roman world and the Germanic civilizations penetrating the Roman Empire. The Roman Empire did not fall, did not decline, it just transformed but so did the Germanic populations which invaded it. To support this conclusion, beside the narrative of the events, he offers linguistic overviews of toponymy and anthroponymy, analyzes archaeological records, studies the urban and rural society, the institutions, the religion, the art, the technology.

Arnold J. Toynbee and James Burke In contrast with the "declining empire" theories, historians such as Arnold J. Toynbee and James Burke argue that the Roman Empire itself was a rotten system from its inception, and that the entire Imperial era was one of steady decay of institutions founded in Republican times. In their view, the Empire could never have lasted without radical reforms that no Emperor could implement. The Romans had no budgetary system and thus wasted whatever resources they had available. The economy of the Empire was basically a Raubwirtschaft or plunder economy based on looting existing resources rather than producing anything new. The Empire relied on booty from conquered territories (this source of revenue ending, of course, with the end of Roman territorial expansion) or on a pattern of tax collection that drove small-scale farmers into destitution (and onto a dole that required even more exactions upon those who could not escape taxation), or into dependency upon a landed élite exempt from taxation. With the cessation of tribute from conquered territories, the full cost of their military machine had to be borne by the citizenry.

An economy based upon slave labor precluded a middle class with purchasing power. The Roman Empire produced few exportable goods. Material innovation, whether through entrepreneurialism or technological advancement, all but ended long before the final dissolution of the Empire. Meanwhile the costs of military defense and the pomp of Emperors continued. Financial needs continued to increase, but the means of meeting them steadily eroded. In the end due to economic failure, even the armor of soldiers deteriorated and the weaponry of soldiers became so obsolete to the extent that the enemies of the Empire had better armor and weapons as well as larger forces. The decrepit social order offered so little to its subjects that many saw the barbarian invasion as liberation from onerous obligations to the ruling class. By the late fifth century the barbarian conqueror Odoacer had no use for the formality of an Empire upon deposing Romulus Augustulus and chose neither to assume the title of Emperor himself nor to select a puppet, although legally he kept the lands as a commander of the Eastern Empire and maintained the Roman institutions such as the consulship. The formal end of the Roman Empire corresponds with the time in which the Empire and the title Emperor no longer had value.

Michael Rostovtzeff, Ludwig von Mises, and Bruce Bartlett Historian Michael Rostovtzeff and economist Ludwig von Mises both argued that unsound economic policies played a key role in the impoverishment and decay of the Roman Empire. According to them, by the 2nd century A.D., the Roman Empire had developed a complex market economy in which trade was relatively free. Tariffs were low and laws controlling the prices of foodstuffs and other commodities had little impact because they did not fix the prices significantly below their market levels. After the 3rd century, however, debasement of the currency (i.e., the minting of coins with diminishing content of gold, silver, and bronze) led to inflation. The price control laws then resulted in prices that were significantly below their free-market equilibrium levels.

According to Rostovtzeff and Mises, artificially low prices led to the scarcity of foodstuffs, particularly in cities, whose inhabitants depended on trade in order to obtain them. Despite laws passed to prevent migration from the cities to the countryside, urban areas gradually became depopulated and many Roman citizens abandoned their specialized trades in order to practice subsistence agriculture. This, coupled with increasingly oppressive and arbitrary taxation, led to a severe net decrease in trade, technical innovation, and the overall wealth of the empire.[6]

Bruce Bartlett traces the beginning of debasement to the reign of Nero. By the third century the monetary economy had collapsed. Bartlett sees the end result as a form of state socialism. Monetary taxation was replaced with direct requisitioning, for example taking food and cattle from farmers. Individuals were forced to work at their given place of employment and remain in the same occupation. Farmers became tied to the land, as were their children, and similar demands were made on all other workers, producers, and artisans as well. Workers were organized into guilds and businesses into corporations called collegia. Both became de facto organs of the state, controlling and directing their members to work and produce for the state. In the countryside people attached themselves to the estates of the wealthy in order to gain some protection from state officials and tax collectors. These estates, the beginning of feudalism, operated as much as possible as closed systems, providing for all their own needs and not engaging in trade at all.[7]

William H. McNeill William H. McNeill (b.1917), a world historian, noted in chapter three of his book Plagues and Peoples (1976) that the Roman Empire suffered the severe and protracted Antonine Plague starting around 165 A.D. For about twenty years, waves of one or more diseases, possibly the first epidemics of smallpox and/or measles, swept through the Empire, ultimately killing about half the population. Similar epidemics also occurred in the third century. McNeill argues that the severe fall in population left the state apparatus and army too large for the population to support, leading to further economic and social decline that eventually killed the Western Empire. The Eastern half survived due to its larger population, which even after the plagues was sufficient for an effective state apparatus.

This theory can also be extended to the time after the fall of the Western Empire and to other parts of the world. Similar epidemics caused by new diseases may have weakened the Chinese Han empire and contributed to its collapse. This was followed by the long and chaotic episode known as the Six Dynasties period. Later, the Plague of Justinian may have been the first instance of bubonic plague. It, and subsequent recurrences, may have been so devastating that they helped the Arab conquest of most of the Eastern Empire and the whole of the Sassanid Empire. Archaeological evidence is showing that Europe continued to have had a steady downward trend in population starting as early as the 2nd century and continuing through the 7th centuries. The European recovery may have started only when the population, through natural selection, had gained some resistance to the new diseases. See also Medieval demography.

Peter Heather Peter Heather, in his The Fall of the Roman Empire (2005), maintains the Roman imperial system with its sometimes violent imperial transitions and problematic communications notwithstanding, was in fairly good shape during the first, second, and part of the third centuries A.D. According to Heather, the first real indication of trouble was the emergence in Iran of the Sassanid Persian empire (226–651). Heather says:

The Sassanids were sufficiently powerful and internally cohesive to push back Roman legions from the Euphrates and from much of Armenia and southeast Turkey. Much as modern readers tend to think of the "Huns" as the nemesis of the Roman Empire, for the entire period under discussion it was the Persians who held the attention and concern of Rome and Constantinople. Indeed, 20–25% of the military might of the Roman Army was addressing the Persian threat from the late third century onward … and upwards of 40% of the troops under the Eastern Emperors.[8]

Heather goes on to state — and he is confirmed by Gibbon and Bury — that it took the Roman Empire about half a century to cope with the Sassanid threat, which it did by stripping the western provincial towns and cities of their regional taxation income. The resulting expansion of military forces in the Middle East was finally successful in stabilizing the frontiers with the Sassanids, but the reduction of real income in the provinces of the Empire led to two trends which, Heather says, had a negative long term impact. Firstly, the incentive for local officials to spend their time and money in the development of local infrastructure disappeared. Public buildings from the 4th century onward tended to be much more modest and funded from central budgets, as the regional taxes had dried up. Secondly, Heather says "the landowning provincial literati now shifted their attention to where the money was … away from provincial and local politics to the imperial bureaucracies." Having set the scene of an Empire stretched militarily by the Sassanid threat, Heather then suggests, using archaeological evidence, that the Germanic tribes on the Empire's northern border had altered in nature since the 1st century. Contact with the Empire had increased their material wealth, and that in turn had led to disparities of wealth sufficient to create a ruling class capable of maintaining control over far larger groupings than had previously been possible. Essentially they had become significantly more formidable foes.

Heather then posits what amounts to a domino theory — namely that pressure on peoples very far away from the Empire could result in sufficient pressure on peoples on the Empire's borders to make them contemplate the risk of full scale immigration to the empire. Thus he links the Gothic invasion of 376 directly to Hunnic movements around the Black Sea in the decade before. In the same way he sees the invasions across the Rhine in 406 as a direct consequence of further Hunnic incursions in Germania; as such he sees the Huns as deeply significant in the fall of the Western Empire long before they themselves became a military threat to the Empire.

An empire at maximum stretch due to the Sassanids, then, encountered, due to the Hunnic expansion, unprecedented immigration in 376 and 406 by barbarian groupings who had become significantly more politically and militarily capable than in previous eras. Essentially he argues that the external pressures of 376–470 could have brought the Western Empire down at any point in its history.

He disputes Gibbon's contention that Christianity and moral decay led to the decline. He also rejects the political infighting of the Empire as a reason, considering it was a systemic recurring factor throughout the Empire's history which, while it might have contributed to an inability to respond to the circumstances of the 5th century, it consequently cannot be blamed for them. Instead he places its origin squarely on outside military factors, starting with the Great Sassanids. Like Bury, he does not believe the fall was inevitable, but rather a series of events which came together to shatter the Empire. He differs from Bury, however, in placing the onset of those events far earlier in the Empire's timeline, with the Sassanid rise.

Joseph Tainter In his 1988 book "The Collapse of Complex Societies" Tainter presents the view that for given technological levels there are implicit declining returns to complexity, in which systems deplete their resource base beyond levels that are ultimately sustainable. Tainter argues that societies become more complex as they try to solve problems. Social complexity can include differentiated social and economic roles, reliance on symbolic and abstract communication, and the existence of a class of information producers and analysts who are not involved in primary resource production. Such complexity requires a substantial "energy" subsidy (meaning resources, or other forms of wealth). When a society confronts a "problem," such as a shortage of or difficulty in gaining access to energy, it tends to create new layers of bureaucracy, infrastructure, or social class to address the challenge.

For example, as Roman agricultural output slowly declined and population increased, per-capita energy availability dropped. The Romans "solved" this problem by conquering their neighbours to appropriate their energy surpluses (metals, grain, slaves, etc). As a consequence of the growing Empire, the cost of maintaining communications, garrisons, civil government, etc. increased. Eventually, this cost grew so great that any new challenges such as invasions and crop failures could not be solved by the acquisition of more territory. At that point, the empire fragmented into smaller units.

We often assume that the collapse of the Roman Empire was a catastrophe for everyone involved. Tainter points out that it can be seen as a very rational preference of individuals at the time, many of whom were actually better off (all but the elite, presumably[citation needed]). Archeological evidence from human bones indicates that average nutrition actually improved after the collapse in many parts of the former Roman Empire. Average individuals may have benefited because they no longer had to invest in the burdensome complexity of empire.

In Tainter's view, while invasions, crop failures, disease or environmental degradation may be the apparent causes of societal collapse, the ultimate cause is diminishing returns on investments in social complexity[9]

Bryan Ward-Perkins Bryan Ward-Perkins's The Fall of Rome and the End of Civilization (2005) takes a traditional view tempered by modern discoveries, arguing that the empire's demise was brought about through a vicious circle of political instability, foreign invasion, and reduced tax revenue. Essentially, invasions caused long-term damage to the provincial tax base, which lessened the Empire's medium to long-term ability to pay and equip the legions, with predictable results. Likewise, constant invasions encouraged provincial rebellion as self-help, further depleting Imperial resources. Contrary to the trend among some historians of the "there was no fall" school, who view the fall of Rome as not necessarily a "bad thing" for the people involved, Ward-Perkins argues that in many parts of the former Empire the archaeological record indicates that the collapse was truly a disaster.

Ward-Perkins' theory, much like Bury's, and Heather's, identifies a series of cyclic events that came together to cause a definite decline and fall.

Adrian Goldsworthy In The Complete Roman Army (2003) Adrian Goldsworthy, a British military historian, sees the causes of the collapse of the Roman Empire not in any 'decadence' in the make-up of the Roman legions, but in a combination of endless civil wars between factions of the Roman Army fighting for control of the Empire. This inevitably weakened the army and the society upon which it depended, making it less able to defend itself against the growing of numbers of Rome's enemies. The army still remained a superior fighting instrument than its opponents, both civilized and barbarian; this is shown in the victories over Germanic tribes at the Battle of Strasbourg (357) and in its ability to hold the line against the Sassanid Persians throughout the 4th century. But, says Goldsworthy, "Weakening central authority, social and economic problems and, most of all, the continuing grind of civil wars eroded the political capacity to maintain the army at this level.".[10]

Environmental degradation Further information: Deforestation during the Roman period Another theory is that gradual environmental degradation caused population and economic decline. Deforestation and excessive grazing led to erosion of meadows and cropland. Increased irrigation caused salinization. These human activities resulting in fertile land becoming nonproductive and eventually increased desertification in some regions. Many animal species become extinct.[11] This theory was explored by Jared M. Diamond in Collapse: How Societies Choose to Fail or Succeed. Also, high taxes and heavy slavery are another reason for decline as they forced small farmers out of business and into the cities, which became overpopulated. Roman cities were only designed to hold a certain amount of people, and once they passed that, disease, water shortage and food shortage became common.

Mining Output Output from the silver mine at Rio Tinto peaked in 79,[12] corresponding to the beginning of the era of coin debasement and inflation and over-taxation. The Roman Emperor debased the coinage because Roman mines had peaked and output was declining. The thesis is that mines of all commodities were being depleted, including gold, silver, iron and so forth. This led to the decline of Roman technological and economic sophistication.

The West Demoted to the Periphery The Western Roman Empire - not the Eastern Empire - fell because the West, including Italy and the city of Rome itself, had been demoted to the periphery. The East had been promoted to the core of the Empire. This occurred on May 11, 330, with the transfer of the capital of the Roman Empire from Rome to Constantinople, by Constantine I. This happened because Greek-speaking Christians - after decades of persecution - took over the Roman Empire. Thus, what little resources of metal were available were used to save the new capital city of the Roman Empire, and its adjacent provinces of Greek-speaking Christian Anatolia. As a result, the Greek-Christian Romans drove all the Germanic invaders toward the pagan Latin West. If the capital of the Roman Empire had not been transferred, then the authorities would have driven the Germanic invasions towards Anatolia, and the West could have been saved.[citation needed]

Late Antiquity Historians of Late Antiquity, a field pioneered by Peter Brown, have turned away from the idea that the Roman Empire "fell" refocusing on Pirenne's thesis. They see a "transformation" occurring over centuries, with the roots of Medieval culture contained in Roman culture and focus on the continuities between the classical and Medieval worlds. Thus, it was a gradual process with no clear break. Brown argues in his book that,

Factors we would regard as natural in a 'crisis'--malaise caused by urbanization, public disasters, the intrusion of alien religious ideas, and a consequent heightening of religious hopes and fears--may not have bulked as large in the minds of the men of the late second and third centuries as we suppose... The towns of the Mediterrean were small towns. For all their isolation from the way of life of the villagers, they were fragile excresences in a spreading countryside."[13]

Historiography Europe in 476, from Muir's Historical Atlas (1911).Historiographically, the primary issue historians have looked at when analyzing any theory is the continued existence of the Eastern Empire or Byzantine Empire, which lasted almost a thousand years after the fall of the West. For example, Gibbon implicates Christianity in the fall of the Western Empire, yet the eastern half of the Empire, which was even more Christian than the west in geographic extent, fervor, penetration and sheer numbers continued on for a thousand years afterwards (although Gibbon did not consider the Eastern Empire to be much of a success). As another example, environmental or weather changes affected the east as much as the west, yet the east did not "fall."

Theories will sometimes reflect the particular concerns that historians might have on cultural, political, or economic trends in their own times. Gibbon's criticism of Christianity reflects the values of the Enlightenment; his ideas on the decline in martial vigor could have been interpreted by some as a warning to the growing British Empire. In the 19th century socialist and anti-socialist theorists tended to blame decadence and other political problems. More recently, environmental concerns have become popular, with deforestation and soil erosion proposed as major factors, and destabilizing population decreases due to epidemics such as early cases of bubonic plague and malaria also cited. Global climate changes of 535-536 caused by the possible eruption of Krakatoa in 535, as mentioned by David Keys and others,[14] is another example. Ideas about transformation with no distinct fall mirror the rise of the postmodern tradition, which rejects periodization concepts (see metanarrative). What is not new are attempts to diagnose Rome's particular problems, with Satire X, written by Juvenal in the early 2nd century at the height of Roman power, criticizing the peoples' obsession with "bread and circuses" and rulers seeking only to gratify these obsessions.

One of the primary reasons for the sheer number of theories is the notable lack of surviving evidence from the 4th and 5th centuries. For example there are so few records of an economic nature it is difficult to arrive at even a generalization of the economic conditions. Thus, historians must quickly depart from available evidence and comment based on how things ought to have worked, or based on evidence from previous and later periods, on inductive reasoning. As in any field where available evidence is sparse, the historian's ability to imagine the 4th and 5th centuries will play as important a part in shaping our understanding as the available evidence, and thus be open for endless interpretation.

The end of the Western Roman Empire traditionally has been seen by historians to mark the end of the Ancient Era and beginning of the Middle Ages. More recent schools of history, such as Late Antiquity, offer a more nuanced view from the traditional historical narrative.