An empire has to be somehow tolerant towards differences between the many nations it consumes. The process of assimilation, even if forced, can and usually does take centuries.
Faith systems are not like that: they require an immediate conversion, and an immediate and willing following the norms.
nine_k says>""An empire has to be somehow tolerant towards differences between the many nations it consumes. The process of assimilation, even if forced, can and usually does take centuries."<
Khan didn't assimilate, he destroyed. Only after his death and the end of his generation of warriors, was his former empire "assimilated" by groups lucky(?) enough to be alive.
The words "tolerant" and "assimilation" have no place when speaking of the advancement of Gengis Khan's armies out of Mongolia.
Just like "faith systems" today have no tolerance, accept no "repentance" and refuse "assimilation".
No organized belief system (includes any religion) is noteworthy for forgiveness and repentance. Such gems as the religious wars in Europe, CCP treatment of Uighurs today, the Inquisition, the Crusades, Genghis Khan, the current Middle East all showed little mercy for unbelievers.
They'll forgive you, maybe let you repent. But then they will kill you, your family, your friends and your business associates.