This play refers in passing to King John's plundering of the monasteries, an action that caused much disagreement during John's actual reign. When he is poisoned by a monk, we see John die as a result of his policy toward the monasteries, despite the play's inexplicable underemphasis of that important aspect of his reign. (His other memorable action, and one of the most important in medieval English history, was his agreement to sign the Magna Carta granting certain inalienable rights to his lords. This document became an important legal foundation for such later landmarks as the United States Constitution, and represents the single lasting deed from John's reign as king. It is not mentioned in Shakespeare's play.)
The Bastard's unswerving loyalty to John makes him spur on the returned English lords to attack Louis, but a peace treaty has been made off-stage between Pandolf and the intractable Louis. Echoing the events outside Angers when the French and English geared up to attack the town but canceled the assault at the last minute, the Bastard here winds up for battle only to have his plans put on hold. It makes for an anticlimactic ending: Battles dwindle because troops were drowned or lost at sea, and enemies seem to come to a peace treaty by default, and offstage at that. The ending suggests that the peace will not last, because the Bastard is still ready to fight--and we know Louis was anxious to try to gain the English throne.
The Bastard speaks the last lines of the play, focusing on the idea of the impenetrable English nation. Yet England is not totally unconquerable, for the Bastard hints that the only real threat to England's power has been when its citizens turn against it. That he speaks these lines after the lords swear allegiance to Henry makes his speech seem like a warning for Henry against these allegiance-shifting lords or an admonishment of the lords themselves. But it also serves as a look ahead at the coming centuries of internal disputes that tore the country apart in the Wars of the Roses--disputes that were not yet completely finalized in Shakespeare's own time.