[quote=lugh]Yeah, I remember that thread, can't find it though.
Long story short, the player spammed as many untis as he could and managed to place them in KHazar just before the Mongols arrived.[quote]
I found the thread if anyone's interested.

https://forums.totalwar.org/vb/showthread.php?t=54233

Looks like the cap is rather low. If anyone has any screenis vs the horde that have a higher number of Mongols than this, I'd be interested in them. Logs or saved battles too.