The poem describes the King's men as:
* "The redcoats came with drums and fife": This suggests a military presence, perhaps a detachment of soldiers.
* "The troopers from the King": This confirms their loyalty to the crown.
* "They watched the moonlit highway": They are specifically watching the road, which is the highwayman's usual route.
The reason they are at the inn is to capture the highwayman, who is a wanted criminal. Bess, who is in love with the highwayman, is being used as bait to lure him into a trap.
The King's men are there to:
* Protect Bess: They are responsible for her safety, even though they are aware of her love for the highwayman.
* Catch the Highwayman: Their main objective is to apprehend the criminal and bring him to justice.
The poem does not explicitly state why the King's men are at the inn, but it's implied that they are there to catch the highwayman. This creates a tense and dramatic atmosphere, as the reader knows that the highwayman is on his way and is unaware of the trap that awaits him.