Henry attempts to assert his claim to the French crown (although there is a difference in interpretation in France and England as to who can claim succession to the French crown), which will require an invasion into France and a battle for the crown, against Charles, the King of France, and his young son, the Dauphin, next in line for the Crown. The tensions between the Dauphin and Henry serve to magnify both Henry’s personal desire for legitimacy and respect, and his desire to show the English people he is willing to fight for them and to do what is right for the country thus adding to his legitimacy as a ruler of England (in order to make up for his past regressions as a youth).
In the Prologue, the reader is given instructions to imagine a great stage, with many more armies and munitions, horses, etc. that can fit on a stage. We are asked to open our imaginations to the trappings of war. In a way, the audience is set up for a glorified depiction of war, not the actual bloodiness, terror, horror, and death implicit in war– a romantic version of war. It is this romantic version that the reader or play-goer gets a taste of Henry’s romantic perception of his role as king and his role as the leader of England. Although Shakespeare attempts to show the brutality of war with some bloody examples and mass killings in the play, the audience is left to use their imaginations and expand the written word to include the horrors of war. That gruesomeness is left to the reader or theater-goer, more than the author.
For Henry V, war is a necessary thing for him to do. This invasion and conquest of France are not taken lightly by Henry and he wants to ensure that he has the moral authority to proceed. He calls on his advisors, Canterbury and Eli, to explain to him in detail the moral justification of this coming war, and wants to be assured from his trusted advisors that his effort has moral standing, which will further establish his legitimacy.