Indeed, the Mongol is very powerful and often rushes quickly in the beginning with massive troops. But they cannot hold for long, friends. There are some tactics we can use.

I usually support in advance to some factions in the front line vs Mongol such as Turks or Khwa to make them busy, I join force with them to fight. Moreover, I usually backstap the Mongol's cities from behind.

Another tactic is that I use a lot of assassin to kill most of their generals to reduce the moral of their troops. In a critical area, I even deploy about 20 full stars assassins.

Hope we can share some good ideas together, friends.