A huge battle is underway as the scene opens, culminating in the retreat of Edward's forces. Edward questions this decision, saying he intends to “pour vengeance” on everyone who is up in arms against their sovereign. Spencer Junior shares his belief that “right will prevail,” but Spencer Senior remarks that their forces are exhausted and need a break from the fight.
Edward and Spencer Junior's faith that their forces will win reflects their broader belief in (as Spencer says) the righteousness of their cause: because they see Edward's right to rule as God-given and innate, they assume that nothing can ultimately threaten it.
Mortimer Junior, Kent, Lancaster, Warwick, and Pembroke appear, and the two sides exchange boasts and insults. Lancaster says Edward's followers will betray him, “traitors as they are.” Spencer Junior throws the charge of treason back at the nobles. Then Pembroke calls Spencer a “base upstart,” and so it continues back and forth. Finally, Edward threatens that the nobles will die for rebelling against their king, and Mortimer questions whether Edward would rather “bathe [his] sword in subjects' blood / Than banish that pernicious company.” Edward replies that he would rather reduce all of England's towns to piles of stone, which Warwick calls a “desperate and unnatural resolution.” The nobles rally to cries of “the barons' right” as Edward's followers do the same in the name of the King.
Once again, Edward and the nobility find themselves at odds over what constitutes treason. To the nobles, Spencer Junior has already proven himself to be a traitor by virtue of the harm he is allegedly doing to both the dignity of the monarchy and to the welfare of the country. That being the case, they suggest, it stands to reason that he would betray Edward. In fact, by this line of reasoning, Edward himself is a kind of traitor, since he continues to demonstrate his basic disregard for England's well-being: in this scene, for instance, he says that he is willing to destroy the entire country in order to get his way. Since the nobles' view of monarchy is predicated on the idea that the king has certain obligations to his subjects (and, of course, nobles), they view this as "unnatural"—a decision that threatens the basic order of society. By contrast, Edward and Spencer's understanding of kinship is based on personal loyalty, which leads them to accuse the rebellious nobles of treason.