Siege.
Because Breanna said so and also because they are very stupid and they are very funny too, just because they are bunnies.
Once a castle is under siege, the people inside the castle are trapped. If they have enough food and water, and can prevent breaches in the castle wall, then maybe they can survive long enough until the besieging force moves away. The main danger inside the castle is that the enemy is able to get inside the castle, there is starvation or dehydration, and that disease is able to become rampant.
I'd say a lot of hard enemies are in Peach's Courtyard and inside Peach's Castle. The ones in Peach's Castle are harder though. The hardest enemy would be Dark Mechawful. (He's a blue robot looking guy and he's in Peach's Castle) Hope I helped!
Siege.
Castle loop holes are narrow vertical slits in the castle wall that allowed bowmen to shoot arrows at the enemy while making it difficult for the enemy to shoot into the castle.
Fire artillery shells at the enemy.
kamakhize you misspelled it KAMIKAZE!!
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These are called murder holes. They were used to drop boiling water/oil, stones and other heavy objects on the enemy.
All in hell goes loose. They had a tactic of hitting and before the enemy could organize they retreated. They 'Harried' enemy troops.
A blockade.
http://download.cnet.com/Return-to-Castle-Wolfenstein-Enemy-Territory-full-install/3000-7441_4-10243510.html