Slavs
Slavs can be further grouped by religion. Orthodox Christianity is practiced by the majority of Slavs. The Orthodox Slavs include the Belarusians, Bulgarians, Macedonians, Montenegrins, Russians, Serbs, and Ukrainians and are defined by Orthodox customs and Cyrillic script as well as their cultural connection to the Byzantine Empire (Serbs also use Latin script on equal terms). Their second most common religion is Roman Catholicism. The Catholic Slavs include Croats, Czechs, Kashubs, Moravians, Poles, Silesians, Slovaks, Slovenes, and Sorbs and are defined by their Latinate influence and heritage and connection to Western Europe. There are also substantial Protestant and Lutheran minorities especially amongst the West Slavs, such as the historical Bohemian (Czech) Hussites.
Ukraine
Poland defeated Western Ukraine in the Polish-Ukrainian War, but failed against the Bolsheviks in an offensive against Kiev. According to the Peace of Riga, western Ukraine was incorporated into Poland, which in turn recognised the Ukrainian Soviet Socialist Republic in March 1919. With establishment of the Soviet power, Ukraine lost half of its territory to Poland, Belarus and Russia, while on the left bank of Dniester River was created Moldavian autonomy. Ukraine became a founding member of the Union of Soviet Socialist Republics in December 1922.