Well, historically the middle east had been occupied by Christians, so why not... I'm playing Poland and I sent 3 crusades to the Holy Land and now I own most of the Egypt and Jerusalem, plus the whole eastern Europe. Mongols are a bit of a pain, but they are not so good at sieging castles when they don't have their siege equipment, so I was able to withstand their push, except for Antioch which I lost after repeated sieges. I'm trying to make the middle east my cash cow, but it takes some time to convert everyone so that they don't rebel and I can squeeze some taxes from the region...