This is on M/M and I guess this is semi gaming the AI due to it being "semi-passive", I label "semi-passive" because the mogols still use their archers to try to shoot the crap out of me, and sometime they would have siege equipment and actively try to storm me.

So around turn 100 the pope issue a crusade on Jerusalem(sp?) it was own by Egypt at the time, and the Mongol is already in play.

I took it with only 1 stack mostly with Crusad merc and religious fanatics/pilgrims(used them as meat fodder), then a jihad was called on the town.

The town had large stone wall and already had a siege work in place so I can build Treb, I proceed to build a gunsmith(bombard).

I started recruiting some archer militia and as much treb as I can build.

the AI would position its unit outside of bowshot, but not outside treb range. So the treb was great in shooting them up.

to speed up the process, sending a catapult or bombard out the front gate would lure the AI to send some unit closer for the archer to shoot at.

I was able to break the siege every turn. half the time the arty would get a lucky shot and kill their general as a bonus.

I was able to upgrade to huge stone wall, with ballastic tower(cannon bug) and cannon foundry(culverin and mortar?) and got in some english longbow as reinforcement.

with this setup I think i have destroyed over 15 stacks over time(mostly mongol some egyptian and some turk). and they still keep coming.

so much so that the mongol who had the most military power in the ranking is now less power than me.

the current stack consist of mix of
1 general
4-8 archer type, longbow prefered, mostly for close in work when it is too close for the treb to shoot without hitting the wall way too often, but i guess Xbow or gunpowder unit may work too
4-6 treb best meat grinder, but difficult to position behind walls if position/aim inccorectly often end up hitting your own wall and sometime breaching it if you are not paying attention.
2-4 mortar easier than treb to position but I feel they are not as good?
2-3 bombard/culverin, sometime you can stick them right outside the gate to shoot up the AI before they have a chance to move in and engage you and you pull back inside, the ground/grazing shot works great and can often go thru 2 to 3 different "unit" (not rank)



P.S. if they have any siege unit, try to destroy them right off the bat.