The kill rate was low, I didn't even notice if for a while. I'll try and move them back a bit next time and see if that helps. I also noticed his gunpowder units were damaging my walls very slowly. I think they only ended up doing about 5-10% damage but it did make me wonder - if they were damaging my walls, could this have been what was killing my troops? or does it only matter when the wall actually falls down?