With a POD of 1900, you’r challenge is to make Poland be divided by at lest 2 countries into the modern day. The most odvious to me are Germany and Russia holding onto their polish territory, but is it possible to have other scenarios? Maybe a Czechoslovakia controlling the southern part of Poland, Germany in the west, and Russia in the east (is it possible for Belarus and Ukraine to also get involved with Russia still having a claim in Poland through winning East Prussia in WW2?)