In Henry V, political legitimacy rests on the right to rule—and the right to rule rests on power. Thus, Shakespeare takes great pains to highlight Henry’s efforts to legitimize a military campaign in France. 

Medieval kings who went to war needed to prove their right to invade another sovereign nation. In 1415, Henry needed to avoid an unprovoked attack on France, which would have turned public opinion against him. 

To make a case for war, he desperately needed the support of the Church, his royal cabinet, and his countrymen. The church–state alliance was a practical consideration: Henry needed considerable financial resources to finance a war campaign. And he needed both the Church and England’s elite to step up. Henry also needed soldiers willing to spill their blood in a foreign land.

Having gained all the resources he needs, Henry emphasizes his power to wage war. He promises the Dauphin that he will “dazzle all the eyes of France” with his “gunstones.” The scaling ladders, crossbows, and massive cannons are as much psychological weapons as they are implements of war, for they are designed to strike terror into the hearts of the enemy. Thus, Henry uses the might of his resources to justify his right to rule and political legitimacy in France.

Henry often invokes the name of God in his battle campaigns. Indeed, throughout the play, religious nationalism is highlighted through Henry’s language. 

Before speaking to the French ambassador, he orders the archbishop of Canterbury to justify an invasion “in the name of God.” Henry maintains that the bishop must speak with a “conscience wash’d as pure as sin with baptism.” On the eve of the Battle of Agincourt, Henry again invokes God’s name to rally his troops. Henry's use of religion to justify his political ambitions seems self-serving on the surface.

This picture becomes clearer when we judge Henry’s actions through the lens of the medieval power structure. Henry’s father, Henry of Bolingbroke, endured political dissension at home and uprisings in Wales and Scotland. In addition, Edmund Mortimer, the 5th Earl of March, had a greater claim to the English throne than Henry himself.

The Southampton Plot to put Mortimer on the throne exposes Henry’s tenuous position. By highlighting the divine assent to his rule, Henry secures his throne and the goodwill of his countrymen. To appeal to “the name of God” is thus Henry’s greatest rhetorical strategy.

Betrayal is a central theme in the play. In fact, betrayal is a common theme in many of Shakespeare’s plays. From Othello to Julius Caesar, the act of betrayal leads to tragic consequences. For the injured party, betrayal is a traumatic experience, as it shatters his sense of security and, in some cases, his inherent belief in humanity. 

In the play, Henry’s betrayal at the hands of the Southampton three is juxtaposed with his own betrayal of Falstaff. It presents a complex portrait of a warrior-king. On the one hand, Henry’s desire for a “just war” highlights his conscientious nature. But, on the other hand, his duplicity, callousness, and self-absorption reveal a Machiavellian nature at odds with his gentler virtues. Even Fluellen, a supporter of the king, unwittingly reveals this ambiguity in Henry’s nature in act 4, scene 7:

As Alexander killed his friend Cleitus, being in his ales and his cups, so also Harry Monmouth, being in his right wits and his good judgments, turned away the fat knight with the great-belly doublet.

In Henry V, the theme of betrayal highlights the complexity of alliances in...