Sid,
Thank you for your welcome.
You wrote:
I have a 1952, English language, Soviet-published encyclopedia of the Ukrainian SSR that shows Ukrainian-speakers as the majority in both Donetsk and Lughansk at that time. It seems that the Soviet Union later imported workers from other parts of the USSR, whose common language was Russian, into these expanding industrial regions and thereby shifted the population balance in later decades. Latvia has inherited a similar Russian minority of similar recent origin.
and
Fascinating. Your link shows that in 1926 three regions of what is now Russia, but adjacent to Ukraine, had a Ukrainian-speaking majority.
Perhaps it is Ukraine that should now be making territorial demands on Russia, and not the other way around?
Donetsk and Lugansk are both situated on colonised land that up to the second half of the 18th century was part of Dasht-i-Kipchak. They were settled as mining areas in the late 19th Century, with colonists coming both from the north, from Russian-speaking areas, and from the west, from Ukrainian-speaking areas.
Thus, Russian-speakers have been a major component of the settler population in the Donetsk and Lugansk regions from the very beginning of colonial settlement under the aegis of the Russian Empire, and have been there as long as Ukrainian-speakers have.
The Bolshevik regime in Russia was the first to officially recognise the Ukrainian and Belarusian nationalities as entities separate from the Russian nationality, and to assign the East-Slavic-speaking population under its control to one of those three nationalities. I do not know what objective criterion the Soviet authorities used for that assignment, presumably native language. Since there are transitional dialects between Russian, Belarusian and Ukrainian, it may well be that in some cases the assignment to one of the three nationalities rather than another was rather arbitrary.
It is noteworthy that in August 1917, the Provisional Government of the new Russian Republic recognised the jurisdiction of the Ukrainian Central Rada stationed at Kiev over the Governorates of Volhynia, Podolia, Kiev, Poltava, and the southern part of Chernigov, but refused to grant it jurisdiction over the Governorates of Kherson, Tavrida, Ekaterinoslav, and Kharkov. Perhaps that was because the Provisional Government considered that the population of those Governorates did not have the same unequivocally Ukrainian ethnic identity as that of the more westerly Governorates.
The Governorates recognised as having a Ukrainian identity had all formerly been part of the Polish Empire, which is why their population had evolved an identity different from that of the population of the northern regions which had come under the rule of Muscovy.
Donetsk and Lugansk were in 1918 both situated in Ekaterinoslav Governorate, an area considered by the Provisional Government as not being essentially Ukrainian in ethnic identity.
In any case, what determines whether a particular area should belong to a Russian or to a Ukrainian state should be the wishes of the population of that area. Not all Ukrainian-speakers, or Russian-speaking descendants of settlers who came originally from the ethnic Ukrainian heartland in the west, feel themselves to be non-Russian, and desire to be part of a Ukrainian state, particularly not one ruled by russophobic Ukrainian nationalists from the western regions.