It's a cheesy tactic, but a very effective one.

I once whipped the biggest portion of the Golden Horde the third move after they appeared with 15 Jihads and every assassin in the kingdom. Killed their general and they retreated. Fought them the next turn, whipped them hard and had 11,000 troops left.

It's very effective against the AI. For instance, you can occupy a province and leave it virtually undefended. If you're invaded -- boom, instant army for practically no cost. I've left juicy provinces open to invasion just for the Jihad opportunity.