Based on a posting in another thread about a grimdark scenario with the Chinese Mainland split between the ROC and PRC...
To be fair that post of my was an off-the-cuff remark, rather than anything I put serious thought into it... not that I'm gonna do any takebacks or anything.
(also funny how this is the second time where a not so serious post from me managed to inspire a thread... and also funny how both times involve posts dealing with lots of people dying.

)
With a POD after 1900 have Poland (defined as any nation with the capital in Warsaw) have a greater population than China (defined as the most populous of the nations that include any of the Historical capitals of China)
Bonus points for use of less than 25 Nukes.
I don't know enough about Poland (I'm pretty sure memes aren't gonna be enough) to speculate on growing their pop for the most part, but I'll take a crack at reducing China's populations... let's be honest though, probably fail the bonus round.
-Poland get's their naval wish-list post WWI somehow (not very important, but might as well throw another joke in while I'm at it), as well as generally more successful in the Polish Soviet War, meaning more territories.
-a longer Russian civil war while we're at it, although still ends with soviet victory... for the most part, maybe missing a few more pieces here and there
-... leading to a more unhinged USSR (as far as foreign relations goes) in the interwar period
-a far less influential China lobby in the US in the interwar period
-a much more brutal second Sino-Japanese war, if that's even possible
-no Western declaration of unconditional surrender of Axis in WWII
-in fact, WWII is more of a 3 way affair between the axis, allies, and the Comintern. There's still plenty of hate for each other going around though
-the major axis powers, while being defeated, still gets some sort of plea bargain deal (mainly as buffers against the soviet threat), this means Japan keep their client state of Manchukuo, their territory of Taiwan, and other bits of China. Basically the Chinese got thrown under the bus
-Poland keeps much of their interwar era borders, somehow, becomes a major power on a par with Italy
-Chinese civil war reach even more brutality, with both (or even more than just 2) sides using chemical and bio weapons on each other (bonus points if some ex Japanese weapons and personnel got involved post WWII). Still ends with communist victory though. (by this point, with a pop of ~300 million, something over 100 million less than OTL by this point, also missing places like Tibet, inner Mongolia, Uyghur, etc.)
-some far east war (akin to OTL's Korean war) gets the US riled up enough to nuke red china a few times to get them to back off on the crazy... it works... sort off... close enough, at least they're not killing people outside their borders...
-with foreign policies a hot mess, Mao (or whoever's in charge of red china by this point) turns inward and goes full pol pot, which means kills a third of the pop, and sending a quarter of the population packing (
so causing the biggest refugee crisis in world history).
-rabid Mao vs. crazed Stalin (or whoever's in the Kremlin by this point) in a war with a higher body count than the one in Twilight of the Red Tzar, some more nukes might be thrown at the Chinese. (think Pol Pot's OTL failed invasion of Vietnam, but on a far larger scale)
-China collapses in another round of civil war, with plenty of countries funneling arms and advisers in, to test out their toys in a live combat environment, WMDs were also part of the weapons tested. Neighboring countries takes a few swipe of territories while they're at it
-what's left of Rump China (singular or plural) is basically a contaminated wasteland with a pop of under 100 million...