the best thing to do is forget about trying to kill them, and finding a way to make your prov, undesirable to attack. in war you need, gold, soldiers, and a build strat that allows only small gains, with as much t/m protection as possible. you already know they are going to have little defense, so have just enough offence to make a good gains attack, with enough defense and guard stations to keep them from getting that land back. the only way to beat the undead is to have an very active kingdom, thriving economy, t/m defense and MV capability, to erase chasity spells, and most important, find a way to keep your lands after you capture it. make your prov undesirable to attack and they will move on and on and on to the next ones, when they realize they are going to be outgained, there spirit and moral will drop like a lead baloon, once that happens its open season.