I even not use word ukrainian anymore.
I'll write a high effort post for Ruskies and bystanders explaining Ukrainian nationality.
South eastern Ukrainians are descendants of Cossacks, while western Ukrainians don't share Cossack legacy and never had their autonomy under both Commomwealth and Russian Empire, but otherwise with time merged into same folk culture and language with Zaphorozhian Cossacks. Cossacks under both Commonwealth and Russians were given autonomy when they were needed for some war campaigns and than had their lands stolen and given to Polish/Russian landlords and turned into peasant serfs as a result of brutally suppressed rebellions, few times.
By the XIXth century, other than Galicia these lands were basicaly Russian colony, Russian landlords rulling local populatian, and Russians migrating to and modernising and developping cities and towns and russyfying what little of local population was allowed to migrate to cities. But majority of local population were slave like serfs, they were owned by landlord, could be physically abused, not allowed to leave their land, needed landlord permission to start a family, could be uprooted from their family and sold to other landlord, could be drafted into army for 10 years. So when you say that Russians born in Ukraine were treated like other Russians in Russian Empire, that is true, Cossacks and local peasants is a different story.
Meanwhile in Galicia under Austrian rule the same ethnically people were practically free in comparison, this is where the modern Ukrainian identity originated and was encouraged and spread into Russian controlled lands. It doesn't mean it was "manufactured", the idea that the same language and folk culture was manufactured by foreign power in lands colonised by Russians for centuries, is completely bonkers. On the other hand after Napoleonic wars, the myth of ethernal friendship between Cossacks and Russian Empire was created and Cossacks from relatively poor agriculturally lands of Zaporozhia were russified while serving in imperial army as cannon fodder for generations. Later during industrialization there was migration of Russian workes to Donbas region and they've bacame an overwhelming majority of urban population there, while during WWII Galicia was ethnically cleared of Poles by banderists and Stalin, while there were never Russians there.
Ukrainian nationalists/ banderists were basically the first generation of free Ukrainian peasants that received modern education, their ancestors were exploited by Russians for generations and while their fathers and grandfathers received freedom and right to own land, russian communists came to steal their land again and make them poorly paid and abused employees in collective farms, just like Cossacks were turned into serfs centuries earlier. During soviet times education, media and official language were russian, so russian became primary language of all educated population and only in Galicia and provincial villages elsewhere people spoke primarily ukrainian at home.
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As for the current situation, before the conflict about half of Ukrainian population were Russians, or russian speakers and were against ukrainian nationalists enforcing ukrainian language on them and voted against them, it doesn't mean they were all pro Russian state. Yanukovych won elections by being pro russian culture and rights to some autonomy of russian dominated regions, but promising to integrate the country as a whole with the west at the same time and got removed by mass protests, when the second part turned out to be a lie. At this point, after all death and destruction brought by Russia probably half of primarily russian speakers consider it to be a lesser evil if their children will receive ukrainian education, but become EU citizens, than to become citizens of USSR 2.0. Claiming that Ukraine is Russia because half of population uses russian language and most of the elite is of ethnic russian origins, is a bit like claiming Mexico is Spain, because they speak Spanish, torture bulls in arenas and most of the elite is of ethnic spanish origins.
