to usesome of the stuff recommended, when you 1st start beign besiegd, a screen should appear with stuff you van build like it does for attack,

instead of showing ladders, rams and towers, it would show hot oil, rocks, logs also large pairs of poles for pushing the tops of ladders over,

the 1st one sup the ladder must quickly kill the pole hodler to stop them pushing over the ladders ( would you allow fallen ladders to be picke dup again?)