There are some mountains and hills near Damascus and Antioch, but for the most part you'll be fighting on plains. The lands down south may be harder, though. The mountain provinces may be hard to take, as enemies can easily use the narrow passes for defense, but once they are take, it is incredibly easy to defend, for obvious reasons. You will have very mountainous terrain in Turkey and Georgia, but as you head south towards Arabia and Egypt, the land becomes completely flat. First off, the campaign map is a mixture of plains and mountains.
Out of the four campaigns for Kingdoms, this one has to be the most intense. It is in this exciting scenario that we being the Crusades campaign. The Empire has suffered much in the past two hundred years, but now it resurges and gains strength, ready for whatever fight may come its way. Spectating this struggle is the Byzantine Empire. The Muslims, for their part, are fighting valiantly to drive back the invaders and reclaim the lands they deem to be rightfully theirs. Believing in the righteousness of their cause, they fight bravely against the overwhelming forces arrayed against them by the Muslim leaders of Egypt and the Turks.
The Catholic crusaders still hold the Latin kingdoms established at the end of the First Crusade. It is 1174, and the Middle East is the stage for a three-way clash of cultures, religions, and ideas.