Thanks a lot, Max, another Rabbit hole for me to fall into. It seems this one leads to all sorts of other holes, so I may be gone a while.
Tartary (Latin: Tartaria) or Great Tartary (Latin: Tartaria Magna) was a name used in the Middle Ages until the twentieth century to designate the great tract of northern and central Asia stretching from the Caspian Sea and the Ural Mountains to the Pacific Ocean after the Mongol-Turkic invasion inhabited mostly by Turkic peoples. It incorporated the current areas of Pontic-Caspian steppe, Volga-Urals, Caucasus, Siberia, Turkestan, Mongolia, and Manchuria. http://www.abovetopsecret.com/forum/thread1067222/pg1
The Tartaria Tablets https://www.cambridge.org/core/journals/antiquity/article/tartaria-tablets/C824E021256A41A254FF5A847EB57E0A
So, where did this country go?
According to theories, Tartaria died in a major civil war that happened in the 18th century. Fun fact: the majority of Russian history was written in 17th-18th century by foreign (mostly German historians).
http://www.abovetopsecret.com/forum/thread1067222/pg1