In my Idea it's a UK of Great Britan, Denmark, Belgium and Ireland.
Im thinking Soviets try to go to war with Poland while in the Civil War and do incredibly worse than otl (or maybe one of the Russian sides cuts a deal with Poland), or Russia tryed to go to war with Poland after the Purges and utterly fails at the art of war.I'm curious how Poland got all of those vassal states. I guess the POD is before the Partitions. Beyond that...no dice.