Thanks for info about G.K. JM - according to Cletus’ comments, GK didn’t get past the Caucauses in Europe. Being unlettered, I accept those who know more than me, but still not sure about G.K. and Slavs...
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1180246/
One of the maps I saw showed the Kahn empire at it's largest to reach to the Western end of the Black Sea and up from there to the Southern border of Finland, to include Moscow ... and half to most of Turkey; down through Baghdad, down to the Red Sea, Persia over to the Western border of India. Other sources claim they reached Egypt. In any case, it was a huge area.