During the era of the Russian Empire and into the Soviet Union, Russification was the strongest policy essentially removing aspects of any ethnic difference to appear more harmonious and as one people. This primarily is seen as enforcing the usage of the Russian language as the dominant or sole language and modifying history to make it as though Russia was the protector or liberator of oppressed groups for example Orthodox Christians in South-Eastern Ukraine such as Crimea when it was under Muslim Ottoman Rule. Another example of this being the fact that during the Red Army's invasion of Poland in 1939 propaganda was issued that it was the Soviets liberating western Ukrainians and Belarusians from Polish landlords. Of course, differences in regards to forming republics on the grounds of ethnicity began to spring in the 19th century the ideas of territory for a people based on shared language and culture and there were famous authors particularly in Ukraine that endeavored to produce writings in their own languages but under Russian rule this was viewed as negative. During the ending days and collapse of the USSR, a language renaissance was spread in order to justify independence and to demonstrate a difference from Russia such as the predominance of say, Belarusian, Ukrainian, Estonian, Tajiki, and Georgian in schooling to name a few. Ethnic differences have also shaped the former Russian republics by replacing the total pro-Russian history and acknowledging faults of Russia such as brutal repercussions and repression of language and culture.