Troops vs magic, what am I doing wrong?

[sector24]

I'm on year 10 in my current game (EA T'ien Ch'i). Typically 1000 guys will roll up to my border starving and demoralized, attack 200 at a time for 3 or 4 turns and then sit in their castle until they get reinforced by another army. The only threat is Ermor because they can't starve and they can skellispam from the back so 1000 guys is actually more like 1500 by the end of the fight. I do lose to the big Ermorian armies without mage support, but most nations buckle like a pilgrim's shoe.