Each defence (gate, wall, etc...) has batter points, which are like wounds. Also each defence as a defence value. A troll with a strength of 7 could attack a gate, then compare its strength to the gates defence.

Some stone defences has a defence value of 100, which means it can only be harmed by things with a strength of 10.

After the attacker has "wounded" the defence they must roll on the batter chart.

1	No effect
2-5	Damaged, score 1 batter point. (strength 10 cause 2 batter points)
6	Badly damaged, score 2 batter points (strength 10 causes 4 batter points)

 

	Stength	Defence	Batter points
Siege tower	-	10	4

The siege tower carries troops to board the walls, they count as a siege target and are quite hard to destroy, exept by a trebuchet. To move a siege tower trolls or orcs must push it. The mumakil also counts as a siege tower as the haradrim in the howdah can jump out if the mumak goes to a wall. P.S you can't buy siege tower, you have to make them.