Greetings and salutations.
This one is based on a short AH story by Olaf Stapledon, called, IIRC, East is West. In it China breaks up in the Middle Ages and stays divided, while the German Emperors succeed in their goal of uniting western Christendom and subordinating the Popes. By the 20th century a sort of mirror image world has come into existence, where the eastern nations are the modern industrial powers, while the west is dominated by a decaying and turbulent Europe-spanning Empire.
Not having quite the Steppe experience of OTL China, the Holy Roman Empire is ruled by a Germanic dynasty with enough local legitimacy that they are still theoretically in charge, although competing revolutionary and separatist groups are stirring up trouble. Planning to use this as an excuse to intervene is the Empire of Britannia, which thanks to its rich industrial resources and strongly centralized government, has managed to modernize like Japan in our world.
The HRE is still struggling to make it out of the 16th century, although there are some hopeful shoots of industrialization here and there. It is heavily Germanized, German dialects being spoken in what our world would be Poland, the Baltic, Venetia, northern France, the Czech republic, and parts of the Ukraine: Latin remains important in Lombardy and the south and west of France. It suffers from severe overpopulation, imports of American food plants by the Asians having brought about a population boom over the last three centuries.
Although the unified Christian Empire managed to do better than OTLs Crusaders, and managed to establish its rule over Egypt, the Holy Land, and much of North Africa, Muslims rallied and were well on their way to driving the Europeans back across the Mediterranean when the Asians put their oar in in the 19th century and to some extents froze things.
Russia, cut off from a hostile Imperial Caesaropapist west and indeed more than once threatened by conquest from it, looked east for civilization and modernity, although retaining their Christianity. “Scratch a Russian and find a Tatar” is truer here than OTL: the Russians became a steppe empire in their own right. (Although there have been some badass pastoralist empires in this TL, there hasn’t been anything quite as apocalyptic as Genghis Khan and Co., so Russia advanced east earlier than OTL). Russians continued to wear robes, did not shave their beards, and studied the works of Kong Fu Tzu (and the many non-OTL glosses on his work). After the revolution brought about by the bloody but inconclusive War of Six Directions (in which Wei lost its colonies) the new government adapted a socialistic regime based on the ideas of Asian philosophers.
The Khanate of Ind, a Mughal-equivalent Islamic empire, is struggling to modernize and keep at bay the Asian powers nipping at its flanks: it is looked upon with some disdain by the major Asian powers, who consider it the Sick Man of Asia.
The Americas or Dawn Lands (Japan is still the Land of the Rising Sun, but the Americas are observably further east) are mostly independent nowadays, the south Chinese and Vietnamese and Nihonese colonies having broken away in previous centuries. Being inconvenient to reach and mostly unpromising jungle and grassland and backwards tribes, the eastern bits were colonized later than OTL: the Nihonese “Brazilian” colony is less populous than OTL Brazil at the time (the Nihonese finally had to use convict labor to get the first settlements going…
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The Kingdom of Dali and Viet played a major role in the early era of overseas exploration and colonization, but has in the last couple centuries declined, being considered nowadays backwards and downright reactionary. Qi and Nihon are long-standing rivals for power in Asia and abroad, while Hubaekje remains a major commercial power. They have kissed and made up due to the rise of Great Wei since the Unification of the Three Northern Kingdoms, and even after the peace of exhaustion in the last war, Wei does not seem reconciled to being merely the first among equals. Now under an extremist neo-legalist regime, it has allied to land-locked (and therefore discontented) Shu and the barbaric but industrialized and regionally powerful Britannians in what seems to be an effort to overthrow the balance of power for good.
Nihon is a power in relative decline, in spite of its still extensive Empire. Its colonies in OTL South Africa, Australia and New Zealand are flourishing, but are also increasingly independent-minded. Nihon perhaps never got over the loss of its Dawn Land colonies, which have since expanded eastwards to become the world’s largest industrial power. Compared to OTLs US, North America is more densely populated in the west and less so in the East: the major surviving Indian populations and tribal lands are in the east rather than the west, having had more time to recover from epidemics before Nihonese settlers arrived, while most tribes west of the Mississippi have been rather thoroughly assimilated. It also has a sizeable European component in the NE, Scandinavian fishermen exploiting the Grand Banks having eventually established settlements after the local tribes were decimated by plagues and before the Nihonese took much interest in that cold, stony-soiled land. Currently the big question is whether the US of the Dawn Lands will interfere in the war many are sure is coming…
Bruce