The Golden Horde
A Tartar people to the north of China brought a number of other Turkish tribes into a military confederation and achieved such a series of conquests as has no parallel in history.
These were the Mongols. Their leader, Temujin, proclaimed himself supreme ruler of all Mongols in 1206 and assumed the title of Genghis Khan.
Genghis Khan invaded China, captured Peking and then conquered an empire that reached from the Pacific to the Volga river, and under his successors nearly all Russia became tributary to the Mongols (or Tartars as the Russians called them) for over two hundred years.
The Mongol rulers were always chosen from the 'Golden Family' of Temujin. The grandson of Genghis Khan, Batu Khan, advanced far into eastern Europe and established in 1251 the rule of the Golden Horde in Russia. As a result, Russia experienced a cultural decay and isolation from Europe, with the exception of northern Russia, around Novgorod, where Alexander Newski was able to preserve some of the north's identity.