Proto Mongols Xiongnu
quite amazing Huo qubing was only a child around 19-20yrs old when he led his army and destroyed the xiongnu
The Xiongnu folks were a mixture between some nomadized Sinic people and Proto-Turkic people.
And the Mongols were a mixture between Turkic people and Khitans.
Genghis Khan's main enemy was the Jin/Jurchen Dynasty (ancestor of the Manchus), and it was his offspring the one who had conquered half part of Europe.
The Tungusic Jurchens/Manchus and Mongols were also long time rivals, and when one side became stronger, and it would also dream to subjugate the other side.