While "honour" is perhaps the play's most important theme, it's also the most difficult concept to pin down. In the mouths of various characters, the definition of honor ranges from being synonymous with an individual's courage on the battlefield to a mere "word" used in an attempt to elevate the physical horrors of warfare to something more lofty and intangible. From Henry IV Part 1's beginning, Hotspur is praised as the very embodiment of honor, while Prince Hal is marked by the "stain" of "dishonour." This allows the play to consider the kind of behavior that makes one a good leader and a strong king. In this way, honor is closely related to the theme of "Power."
Henry IV Part 1 suggests that "honour" is a noble and necessary attribute for all successful leaders and monarchs.
In Shakespeare's play, "honour" is revealed to be a thin concept that some men use in a fruitless attempt to elevate the gruesome realities of warfare to something noble.