A Red-White Civil War in Post-WWI Germany?
In our history, although there were Communist uprisings in various parts of Europe after the First World War, when people think of Reds and Whites they think of the Russian Civil War in what became the Soviet Union.
However, there was a Communist uprising in Germany (and even a short-lived Communist regime in Bavaria) that got scotched pretty quickly.
But what if they hadn't? That's the plot of the alternate timeline "Rosa's Reich," in which Communist leader Rosa Luxemburg's people manage to seize power in parts of Germany after the fall of the Kaiser and the end of the war. Luxemburg, to her credit, strongly opposed Lenin's authoritarianism and gangster tactics and seemed to really believe in workers' democracy, so if her Reds manage to defeat the German Whites, such a regime would be much more humane than the Russian one.
And it would be a useful way to remove a young Adolf Hitler from history. Some historians think he briefly served the Communist regime in Bavaria, while other material I found suggested he remained part of the regular German military, joining the embryonic Nazi party to spy on them and drinking the Kool-Aid. Either way, a German civil war would allow for plenty of opportunity to kill him, disable him (which would likely prevent his historical political career), or send him down a different life path altogether. Even if the Communists ultimately lose, a German equivalent of Admiral Horthy in Hungary would be much better than what ended up happening.
*Although Rosa and friends don't go so far as to allow the embryonic Strasserists into their coalition and ultimately don't allow the Social Democrats (SPD) either, there are all sorts of interesting characters who are part of it. Christian Communists, anarchists, etc. Germany's Overton Window hasn't shifted as far to the left as Russia's and leaving out democratic parties like the SPD isn't cool, but this could lead to a very interesting Red regime.
*The battle sequences are quite interesting and well-crafted. So far they're pretty small-scale owing to Germany's military collapse, but they can always get bigger.
*The successful Communist revolutions (and even the less-successful ones) were confined to Eastern Europe in our history (Hungary had a brief Communist dictatorship, there was a Red-White war in Finland, the Freikops helped prevent the Bolsheviks from taking over the Baltic states). However, with the Communists gaining strength in Germany and a strong reluctance of the Allies' tired soldiers to intervene, it's possible the revolution could spread into Scandinavia and possibly even France. Europe could look very different this time around.
*Luxemburg was partly Jewish and partly Polish, so her ruling Germany is particularly ironic given it's actual history. I'm not aware of any non-monarchical female world leaders until after WWII at least, so this is even more interesting.