hell, I set up my defences against the horder - the only time I've actually met them - based on the rivers and the rivers only. You can defend 4 provinces in a thin blue line Kiev right round, and mass a larger cav and pavise based force in the province north of Khazar. Gotta kill the horde quick though, that level of armies was a serious drain.

But the horde were a huge disappointment. only 3 full stacks, and one of those was siege engines.

So I moved in with everything, drove off the main force and trapped the Khan in the Crimea with 2 units of MHC. then kept him there, raiding once in a while with my jedi general (9*, skilled attacker) to make sure he wasn't going anywhere with his army.