他用一个巧妙的计谋骗过了守卫，成功悄无声息地进入了城堡。

His clever ___stratagem fooled the guards and allowed him to enter the castle unnoticed.

他假装撤退的计策成功引诱敌人进入埋伏圈。

His ___stratagem of feigning retreat successfully lured the enemy into an ambush.