Mongol Empire

but where did the name Volga come from then? (Lake Balkhash - from the state of Balkh)
Volgaria was located in the area where the Kazan Khanate was later formed.

the word "khan" is a simplified form of "khaan," or more precisely, "khagan."
"Princess" Olga was initially a "konung," that is, "the wife of a king."
then these words were forgotten, and a new word "prince" appeared.
"Tati" or "Tatars" in Old Slavic meant "robbers" or "raiders."
(hence the saying: an uninvited guest is worse than a "robber").
some linguists say "Kara-Kitan," others "Kara-Kitai."
http://dic.academic.ru/dic.nsf/ruwiki/955212
and the English called the Chinese city of Guangzhou "Canton."
so, let's not get bogged down in nitpicking.

I think that the expression "Volga Bulgaria" is redundant.
and to avoid confusion with that Bulgaria, which is on the Danube (and which supplied us with "Bulgartabak"),
I named it in our own way.

I played through the red campaign on the highest difficulty.