Why Rome had to fall
The history of the progress of civilization is simple - civilization begins in some fertile place or other, where it, as a wheel that is given a turn, stagnates after a few centuries of development. It then, after a few more centuries, expands to a neighboring region, where it, as in the parable of the sower, stagnates at an even lower level than its origin (as in, e.g., Ethiopia) or moves to a higher level and similarly stagnates after a few centuries (as in, e.g., southern China). The question is why this process is not smooth, but can suffer abrupt reversals. The most prominent such reversal is undoubtedly the receding of the tide of civilization away from Britain, Gaul, Spain, and Italy and toward the Middle East with the collapse of the Roman Empire in the West and Justinian’s wars.
The above chart is simplistic, yet true. There was more intellectual and economic progress in Europe during the first quarter of the twentieth century than there was during the whole period between Augustine and the Renaissance. The question is why world progress had to be temporarily confined to the southerly parts of the globe while the Global North retreated into semibarbarism -why the wheels of progress had to spin in the opposite direction in Western Europe.
In the second quarter of the first millennium AD, both the Roman Empire and the Chinese Empire suffered catastrophic wounds at the hands of their “five barbarians” from the North. Yet, while China recovered (though, for various reasons, did not succeed in starting the industrial or scientific revolutions), the Roman Empire did not. The reason for this is simple -until the eighteenth century, there were hardly any people in Manchuria, while Germany could, due to steady population growth, start its own “Holy Roman Empire” independent of the Roman lake, which made the Mediterranean’s political reunification impossible.
The history in the West goes like this
Rome builds a civilized, literate Trier (first and second centuries AD, analogous with the 汉朝)
a “Gallic Empire” is established (equivalent to China’s 三国 era)
both Rome and the Gallic Empire are destroyed by barbarians (fifth and sixth centuries, analogous to China’s fourth century)
the Gallic Empire recovers, this time being centered around the Blue Banana (seventh to ninth centuries, roughly analogous to China’s 西魏)
The economic move southward seen in the Roman empire region (so called by Scheidel) during Late Antiquity also happens in China -there was no great difference between the great Caliphates of the early and central middle ages and the 宋 dynasty. As in the case of Theoderic’s tomb in Italy, there was plenty of monumental construction in northern China under barbarian rule. Trier was located in the same place for the Roman Empire 北京 was to the Chinese empire. Yet, even in the eighteenth century, 北京 was as much a border zone to China as Trier was to the Roman Empire in the fourth century. Simply put, the 金 Dynasty -China’s equivalent of the Kingdom of the Franks -was much less viable due to the much smaller population behind the Ming Great Wall.
Both the North China Plain and Western Europe ended up recovering during the central middle ages. The great difference, however, between the Empire of China described by Marco Polo and the Roman Empire of Aristeides (thanks to Kaldellis’ Romanland for the reference) was a simple one: the Roman Empire had a vast potentially fertile Northern European Plain bordering it; China only had Manchuria. And unlike Germany, Poland, and Russia, Manchuria in the nineteenth century was still China’s Hungary. Only in the twentieth century did it surpass Germany in population. The Chinese equivalent to the Western European Frankreich was a northern Chinese dynasty centered on 北京 and controlling both Manchuria and the north China plain. Pre-Mongol China often had this. Its equivalent to Italy, however (the region around 西安), was strong enough to claw back power from the barbarians during the sixth century, while the actual Italy was destroyed by Ostrogoths, Romans and Lombards and divided into a kaleidescope of city-states.
It is as if in China, Manchuria had become a more populous region than that around 西安, and, thus, Manchuria and the north China plain could not be conquered by the Mongols. The 金 dynasty would have hypothetically had a role similar to France in Europe, with 开封 playing the role of Paris. Notably unlike actually existing Medieval Manchuria, however, Medieval Germany was divided, fairly densely populated, and free of the threat of steppe nomadism -the Mongols only destroyed Russia and Hungary, not Poland and Germany. The role of the Mongols in China was as if Mongolia had first destroyed Hungary, then invaded, as the Huns did, Austria, Germany, France, and Italy, and (much unlike the Huns), after forging a unified Western European state, failed at attacking Britain. Ultimately, the Mogol invasions of Europe resulted in the creation of a system that would unify only one country -Russia.
What does this have to do with the long Italian stagnation? Simple: for Germany to rise, both Trier and Rome had to fall -and the new center of Western European culture had to be centered around Trier, not as a frontier zone as in the fourth century, but as a core region between settled France and settled Germany.
Remember the famous quote from Seneca:
Who can be braver than the Germans? Who charge more boldly? Who have more love of arms, among which they are born and bred, for which alone they care, to the neglect of everything else? Who can be more hardened to undergo every hardship, since a large part of them have no store of clothing for the body, no shelter from the continual rigour of the climate: yet Spaniards and Gauls, and even the unwarlike races of Asia and Syria cut them down before the main legion comes within sight, nothing but their own irascibility exposing them to death. Give but intelligence to those minds, and discipline to those bodies of theirs, which now are ignorant of vicious refinements, luxury, and wealth, —to say nothing more, we should certainly be obliged to go back to the ancient Roman habits of life.
Athaulf, Clovis, and Charlemagne were all part of the same process -Germany writing.