Rather Large Historical Error

[Paradox]

Perhaps they needed more Muslim factions in the game? Since the amount of Muslims and Catholics, the two main religions in the game, are unbalanced. Or maybe the Mongols were required to have the skill to call a jihad in order to uphold their strong momentum of capturing city after city, since other faiths lack the ability and unity to call their own religious campaigns.

The Golden Horde, I believe, was Christian and at one point offered to help Christendom rid themselves of the Muslims in a pincer attack from both east and west, it was rejected.

Might I ask why it was rejected? Why would Christendom pass up such an opportunity to defeat those who have been impeding their expansions and their main opposition of the occupation of the holy land.