Genghis Khan II - Great classic game!
As mentioned above, the AI is not very bright, so there's alot of holes that you can exploit to make the game very easy..
I finished the game countless time, trying every ruler in every campaign by exploiting the AI's weakness..
It was fun, though..
My basic strategy is getting cash as much as you can, by trading with merchants or plundering enemies town / castle.
Use the cash to buy the best unit (My personal favorite is Horse Archers and Samurai).
Train and buy Arms until both are at 100, then launch the attack.
If the enemy has more units than me, I usually use the "Hit and Run" tactics, attacking with only 1-2 legions and try to destroy their weaker unit, then withdraw without losing any unit.
Repeat that in the next turn, and you will be able to beat a state with 20 units with only 8 units
I don't know if any of you already notice, but there are also some hidden Generals in the game, like Robin Hood in certain scenarios. I forgot the details, though.
Overall, it is one of my favorite classic game of all time