Quote Originally Posted by Monk View Post
From the start you're right, Rum is just too powerful to take in a head on fight. Waiting for the opportune chance while consolidating is your best bet to take them out. Assassinating their sultan while they have a child heir and spamming their more powerful vassals with your chancellor's "ruin relationship" is a good way to precede an invasion of someone more powerful than you.

The Sultanate of Rum has zero internal problems at the start - it's up to the player to create some strife.
Not to mention the ability to holy war the entire west.