Final answer:
The emperor commands his troops to march between Gulliver's legs as a foolish spectacle, highlighting his vanity and incompetence.
Step-by-step explanation:
To show the emperor's foolishness, the author has the emperor command his troops to march between Gulliver's legs for spectacle and amusement.
This act symbolizes the emperor's misplaced priorities and his lack of true leadership by focusing on absurd displays rather than substantive governance.
The emperor's actions are meant to illustrate a broader commentary on vanity and incompetence in positions of power.