Threat is all fine and dandy, except it only annoys the player, and not the main muslim nations, who not only grow large but never implode.
Yeah, that's my big problem. Right now in my game there's
two AI-on-AI coalitions (one Catholic, one Muslim) against the Byzantines which seem to have blown up after they successfully holy-warred for Aleppo a while back (they've also crushed a sh*tload of revolts and shipped out troops to help me at least once, but I don't know if that counts). Meanwhile you have the Umayyads dominating Spain except for a piece I helped Aquitaine reconquer, the Muhallabids controlling the entire Sahara and the western half of the Persian Gulf down to Abyssinia, and whichever Muslim controls the Middle East, and
none of them get a defensive pact to keep them from, well, doing exactly what they're doing right now which is trying to holy-war Barcelona back from Aquitaine.
I have to say, they picked a great time for it: due to a f*ckup of my alliance network I'm currently
enemies with Aquitaine over them trying to snatch Middle Francia (I had the Aquitainian alliance,
but not the non-aggression pact, deactivated because I didn't need them for a quick land-grab in Britain), so I can't move in to help keep the Sheikh of Castilla from taking Barcelona back for the Umayyads.