I exterminate all cities I conquer to keep order and make some profit out of it by the way. Oh I pretty much backstabbed Hungary as when their was fighting the Mongols I attacked them and now they only have Sofia left. I also used Constantinople and my Black Sea bordering Settlements to send a army to take Khazak and Crimea. I held on to Constantinople during the Mongol invasion so I it I took back Nicaea and other settlements in Antolia without to much of a hassle. I asked for a Crusade on Acre and used the Crusading mercenaries to bulk up on my invasion army after the course through Alexandria, Cairo, and Gaza. Later on I used my navy and loaded up my army on North Africa and started retaking Egypt. They never bothered to cross the massive desert that is North Africa and was stopped by Hungary, Venice, and Poland. In my campain so far the Mongol invasion is pretty much expanded as far is it can go wiping out Russia, the Turks, Egypt, and the Byzantine.

Oh yah a tip to conquer other Christian nations is to attak them, give gifts of 100 florins to the Pope so your relationship won't go down, and wait for them to attack you so they get exommunicated first.

I usually play as the Christian Countries bordering the med such as Sicily, Milan, Venice, and others.

Medieval 2 total war holy roman empire