As indicated at the close of Henry IV, Part II, King Henry V is planning on entering into a war with France over some disputed lands and titles. He has instructed the Archbishop to be sure that his claims are valid. When the play opens, the Archbishop explains to his Bishop how he plans to convince the king to enter into a war with France, thus protecting the church's property, which might otherwise be placed in the hands of the state rather than left in the church's control.
After the king is convinced of the validity of his claims, an ambassador from France arrives with a rejection of the claims; he also delivers an insulting barrel of tennis balls from the French Dauphin, who still considers King Henry to be the silly and rowdy Prince Hal.
As they are on the verge of leaving for France, King Henry is tending to some business — releasing a prisoner for a minor offense — and then he turns to three of his trusted advisors and has them executed for conspiring with the French to assassinate him. Meanwhile, in the French court, no one seems to take Henry seriously. The entire court is contemptuous of his claims and of his abilities. They are so overconfident that they do not send help to the town of Harfleur, which Henry easily conquers. After this victory, Henry gives strict instructions that all the citizens are to be treated with mercy and that his soldiers are not to loot, rob, or insult the native population. However, a companion from Hal's youth, Bardolph, an inveterate thief, steals a small communion plate, and, as a result, he is executed.
In spite of the English victory, the French still do not express concern, even though the Princess Katharine is involved; if Henry is victorious, she will become Queen of England; as a result, she feels the necessity to learn the English language, and so she begins taking instructions in that language. Meanwhile, the reports that the English are sick and tattered allow the French to prepare for the battle with complete confidence, especially since they outnumber the English 60,000 to 12,000 troops.
Just before the crucial Battle of Agincourt, an emissary once again approaches King Henry with demands that he immediately surrender his person. His demands are rejected, and King Henry, in a patriotic speech, urges his troops to fight for "Harry, England, and St. George." By miraculous means, the English are victorious and the French are shamed into submission. At the end of the play, King Henry's demands are granted, and he is seen wooing and winning Princess Katharine as his future queen.