Russia is really the the only large colonial power that didn't de-colonize after WWII. That's why you have soldiers from Asia with mongoloid features speaking Russian committing war crimes in Ukraine. They've been weaponizing their purposefully impoverished minorities to fight their wars. There's a reason Dagestan is exploding. They've already had 10x the per capita casualties of Moscow. A draft there would be brutal.
Zelensky understands this and has begun appealing to Russia's minorities to resist Russian colonialism and imperialism:
An interesting observation.
Russia's colonialism, of course, was structured a bit differently than that of Britain or France, in that it was largely territory contiguous to Russia, or her initially expanded empire, as opposed to being on other continents. As with the UK and France, colonialism did see the spread of the colonializer's language, but perhaps more so than typical in the former cases, it also saw the spread of ethnically Russian people into the acquired territory. (though this obviously happened in a large way for Britain in North America and Australia, displacing those who were indigenous over time, as the majority); but not so in India or most or Africa.
Looking at areas that are, today, ethnic Russian, vs those that are not gives one a sense of what may happen here.
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One additional note, China was not typically thought of as a colonizer; yet, much of today's China is not ethnically Han Chinese, and may still not have Mandarin as a mother tongue. Fully 1/3 of Chinese citizens are not native Mandarin speakers.
Divisions in China do exist today. In the west, we might think of Tibet or the Uyghurs (who are mostly Muslim), though there are other regions. I don't consider myself sufficient expert on China to discuss whether serious secession movements are plausible there. But that's something that always come up in the context of China engaging Taiwan, is whether those with domestic grievances might try to use such a moment to their advantage, and how cognizant China is of that risk.