The main idea of this scenario is that the OTL Common Era evolutionary paths of western Eurasia and eastern Asia are swapped, broadly speaking, as much as it may be plausible (assuming that geographical determinism is a totally fallacious and wrong concept).
Some mandatory and optional events to define the scenario:
- After the collapse of the Han Dynasty, Imperial China permanently breaks down into several states, none ever getting lasting size or population greater than Japan, Korea, or Vietnam, that develop their own distinct culture and separate national consciousness, and in most cases, their own language.
- A loose supranational cultural identity, based on Chinese influence (the "Sinosphere"), nonetheless evolves that by modern times comes to encompass all of East Asia, Southeast Asia, and OTL Russian Far East.
- Classical Imperial Rome manages to purge itself of the domestic flaws that IOTL caused its fall (largely by the means described
here) and evolves into a united civilization-polity with a very strong national consciousness, cultural identity, and Latin-Greek linguistic homogeneity that always manages to pull itself back to political unity despite possible occasional periods of political disunity. Occasional inroads of barbarians, if they ever happen, are invariably and efficiently absorbed within the Roman civilization-polity. Its lasting borders come to include all of continental Europe (minus Scandinavia), North Africa, Nubia, Anatolia, the Levant, Mesopotamia, and Arabia. Eastern borders at the very least reach the Vistula-Dniester line and the Zagros Mountains in classical times, by modern times they may remain as such or be expanded to the Neman-Western Bug-Southern Bug line. To mark the classical eastern border of Rome, a massive line of fortifications exists that stretches from the Baltic Sea to the Black Sea (the "Great Wall of Europe").
- Rome fails to conquer and assimilate Britain (optional) and Persia. Those areas receive some Roman cultural influence and may be conquered or vassallized for a while, but never long and well enough to allow their lasting assimilation in the Roman polity. They keep/develop their own distinct culture and national consciousess, in the case of independent Britain a mix of Celtic, Norse-Germanic, and Roman elements.
- Rome gives up the conquest and assimilation of Scandinavia (due to perceived poor value) and of Sarmatia (due to perceived poor defensibility). Both areas receive some Roman cultural influence but develop their own distinct culture and national consciousess, Scandinavia mostly Norse-Germanic with some Roman elements, Rus a mix of Slavic, Norse-Germanic, and Roman elements.
- Islam is completely butterflied out due to Roman assimilation of Arabia, Christianity is snuffed out in western Eurasia (much like Buddhism was in India). The mainstream religion of Rome becomes a syncretist fusion of Greco-Roman, Celtic, Germanic, Egyptian, and Levant polytheist Pagan faiths with strong monist elements, very akin to Hinduism ("Romanism"). Persia remains Zoroastrian. Independent Britain, Scandinavia, and Rus evolve their own "national" Pagan religions, broadly similar but distinct from Romanism. Buddhism spreads to western Eurasia and becomes its secondary mainstream religion, which exists alongside Romanism or the local equivalent in a complementary, non-competitive relationship similar to the one that exists IOTL between Buddhism and Shinto or Chinese folk religion.
- (optional) Christianity spreads to eastern Asia (in a way similar to the OTL diffusion of Nestorian Christianity to China) and in due time displaces and replaces Buddhism, Shinto, and Chinese folk religion as the mainstream faith (not necessarily as a single confession) of East Asia and Southeast Asia.
- Rome and the Sinosphere powers always remain at least as culturally and technologically dynamic as OTL China and OTL Europe, respectively. Both undergo colonial expansion during the Early Modern period (Sinosphere akin to OTL Europe, Rome akin to an OTL early Ming China that never suffers a swing to isolationism, with the inevitable geopolitical differences).
- The Sinosphere develops industrialization first, but Rome embraces it fast and well enough to prevent its own colonization by foreign powers.
- By modern times, the Sinosphere is at least powerful and wealthy enough as OTL Europe, Rome as OTL China.
A note: the author of the scenario is very well aware, due to past discussions, that it, or some key elements of it, may turn out rather controversial with, and disliked by, certain board elements, for various reasons. I make a plead for everybody to take part in the discussion only if you are willing and able to make a
constructive contribution and
helpful suggestions about the concept of western Eurasia and eastern Asia evolving this way. If you honestly deem the scenario to be too implausible or distasteful to fulfill and have nothing else to say on the subject apart from naysaying, please stay away from the thread, and assume that your naysaying arguments, due to past lenghty discussions on similar subjects, are already known, noted, and overruled.