Mission 9. Not a hard, but not an easy mission either.
I try to help you, but I doubt if it really helps xd
First, lure the northern enemy to your town group by group, kill them with your troops. While doing so, build an economy. Have these (or more, but I doubt if you can get more within that little space): 4 farms, 2 pigfarms, 1 mill, 1-1-1 butchery, bakery and tannery, 2 armory workshops, 5-6 woodcutters, 3 sawmills, 2 weapon workshops, 2 gold and iron mines, 2 metallurgist's, 2 iron smithies (/smelters), 1-1 weapon and armor smithy, maybe 1-2 vineyards. Train lancers and crossbows. Be aware of the AI attack after 50 minutes or so (I can't really remember the exact time, you will get a message anyways), hitting your town from between your gold and iron mountains. Push forward north, until you reach the north-eastern enemy. Lure them group by group. After that, crush the enemy in the eastern centre. He shouldn't have too many troops since he has to build a town himself first. Have fun and good luck
P.S.: if you are playing the original game, not using weapon and armor smithies but siege workshop and producing ballistas will come in handy. In that case, make many lancers and mass ballistas plus 1-2 bowmen for luring.