storming castles

[sushiboat]

Mindless troops siege at full strength; they are 1/10 for defending only.

In addition to the above suggestions, use a flying supercombatant (SC). If it doesn't fly naturally, give it Winged Shoes. Put it in the front and to one side, with orders to hold (or cast buffing spells) for at least two turns. During the turns that the SC holds, the enemy troops will rush forward into the gate, where your other troops will be going. Then the SC will have a good chance of being able to attack enemy commanders quickly.