flooding a castle; inundating a castle
Historical siege tactic of diverting a river or building a dam to flood a castle's defenses or force surrender.
During the Warring States period, the tactic of flooding a castle was used to capture it.
cutting off a castle's water supply
Another historical siege method: blocking or diverting a castle's water source to force surrender through thirst.
Water-based siege tactics also include cutting off a castle's water supply.
Compound of 水 (water) and 攻め (attack, siege), referring to siege tactics involving water.