@RogerCooper "Russia leaves the war if x number of its territories are occupied" sounds good to me. I would simplify it even further, if anything. Like:

It's no longer optional.
No more "after Round 4" condition.
Not even the "only territories close to Moscow or Petersburg" condition.

@Schulz This your mod, you don't have to the same way as the boardgame. Essentially the Russian Revolution means that Russia goes neutral and possibly some territory is transferred. The trigger is a combination of territorial losses, time and luck.

"The Russian Revolution" doesn't trigger in World War I 1914. I assume it's not possible to implement it in the current engine.

What could we do instead that would be feasible to represent it?

Something simple enough that doesn't mess up the AI?

I divided Brest and Vilnius.

I think it would be way too easy to defend against the Russians if territories 2 and 4 were merged. I was initially hesitant because I've always hated how, on the Great War map, it's a no-brainer for the Russian player to just hold the Belarus–Kiev–Warsaw line. (There's a similar issue in Domination 1914 as well.) It was also a no-brainer for the Germans to follow that route. Territory 4 (Brest) shouldn't create the same issue, and luckily I don't think it will, because:

In the Great War, the key territory (Kiev, which blocks both the German and Austrian advances at the same time) is four territories away from Berlin and Vienna, but here it's much closer. The Central Powers will also have Hungarian and Prussian factories. The Russians will also get an increasing IPC penalty each round, so they won't be able to easily hold territory 4 and block the routes. Plus, the Austrians can move 7 in that case and take Kiev if Russia undercommits to that front.

Territory 4 should probably be worth the fewest IPCs to offset its strategic importance. I'm still not a fan of it, but combining territories 2 and 4 sounds even worse to me. I don't know—maybe I can find another way to further reduce the importance of territory 4.

I'm also not sure how to handle the Serbian front. Austria taking on Serbia while holding Galicia at the same time in 1914 was highly unlikely. In most games, Austria shouldn't be able to do both.

Another issue is how to represent the Serbs. Having the Russians represent them would be problematic since all Russian units are meant to be removed if the Revolution triggers. Serbian units shouldn't disappear just because of the Russian Revolution.

I don't like making the Serbs Allied-neutral either, since it would let Austria move everything to the east until Italy enters the war in Round 4.