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Maybe this requires hand-waving. I realize that the Polish troops who took Kiev in 1920 were clearly over-extended. But let's just say that something--more foreign help, some terrible military mistakes by the Bolsheviks, whatever--leads to the Poles and their ally Petliura managing to take all of Ukraine west of the Dnieper from the Bolsheviks--and hold it. (Yes, I know that to complicate things, Wrangel was still around. But I'll assume that the Bolsheviks still defeat him and take control of Crimea, which as in OTL presumably becomes part of the RSFSR.)

Ukraine is then divided in two--the Ukrainian SSR on the left (east) bank, and Petliura's Ukrainian People's Republic on the right (west) bank, including Kiev. Actually, Ukrainians will be divided among five nations:

(1) The Ukrainian SSR, soon to become part of the Soviet Union. It contains truly "Ukrainian" areas like the Poltava guberniya, but also heavily Russified areas like the Donets Basin. Unlike OTL, its capital remains in Kharkov after 1934.

(2) The Ukrainian People's Republic.

(3) Eastern Poland--Petliura had to concede eastern Galicia, western Volhynia, etc. to Poland in the Treaty of Warsaw http://en.wikipedia.org/wiki/Treaty_of_Warsaw_(1920) as the price for the military alliance against the Bolsheviks. This was, needless to say, an unpopular decision among many Ukrainians, especially West Ukrainians.

(4) Czechoslovakia (Subcarpathian Ruthenia).

(5) Romania (northern Bukovina and southern Bessarabia).

What are the consequences? How badly will the loss of right-bank Ukraine hurt the Soviet Union? What are Petliura's prospects? It seems to me that he is going to be heavily dependent on the Poles, and for this and other reasons will probably not be very popular, but can he nevertheless survive? (He will of course condemn all his internal opposition as Bolshevik-inspired--and some of it will indeed be so.)

(Pilsudski's own explanation to Wasilewski was that "we shall oppose the Ukraine of Petliura to the Ukraine of Rakovskii" and "let the Ukrainians decide for themselves." He added that he would demand a neutralization of Kiev and a constituent assembly for all Ukraine. Belorussia, however, was to be a purely Polish concern. Quoted in Piotr S. Wandycz, *Soviet-Polish Relations, 1917-1921*, p. 170. Of course if the Poles were strong enough to demand all this, one wonders why they wouldn't just go all the way to Moscow as in 1610. :p But I don't think the Poles and their Ukrainian allies keeping everything west of the Dnieper is ASB territory, though it is unlikely.)
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