AHC: Iranian South Russia/Ukraine

You are millions. We are hordes and hordes and hordes.
Try and take us on!
Yes, we are Scythians! Yes, we are Asians -
With slanted and greedy eyes!

Alexander Blok, "Scythians," 1918. http://max.mmlc.northwestern.edu/mdenner/Demo/texts/scythians_blok.html

Much of what is now southern Russia and Ukraine was once dominated by Iranian tribes--Scythians, Sarmatians, Alans. In modern times, all that is left of them are the Ossetians. (At least that's all that is left linguistically--of course some East Slavs may be descended in part from Slavified Iranian-speakers.) Is there any plausible way to have a much larger Iranian presence in Russia and Ukraine lasting into modern times?
 
Strangle the ottomans and Tamerlane in the cradle, have Persia unite in the 1300s/1400s and conquer into Anatolia, eventually they clientize Tartarstan (so it will be named) in Crimea Astrakhan etc just as the Ottomans tried to do.
 
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