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

stratagem 来自希腊语 strategema（军事计谋），由 stratos（军队）和 agema（领导）组成。这个词指精心设计的计策或策略，常用于军事或竞争场合，带有"巧妙设计"的意味。