Prince John of Lancaster (so named because he's a prince and was born in Lancaster) is one of King Henry's son. In Part 1 Prince John is relatively a minor character but he's responsible, respected by the nobles at court, and fights courageously at the battle at Shrewsbury. In Part 2, Prince John plays a larger role as the leader of his father's army. He's notable for the way he tricks the rebel leaders. After promising to "redress" the rebels' grievances, he convinces them to disarm and then…Surprise! They're all under arrest and slated for execution.
There are a two different ways to read this: 1) Prince John's shrewd political maneuvering is evidence of his loyalty to the king – he did what was necessary to bring down the rebellion and deserves major props. 2) Prince John's shrewd political maneuvering is unjust and dishonorable – Prince John is no better than, say, Falstaff, who also runs around deceiving people. (We're thinking of Falstaff's swindling of Mistress Quickly in particular. Recall that he promises to marry her, convinces her to lend him a bunch of money, and then doesn't keep his word.) So, what do you think? Is Shakespeare showing us that there's little difference between Prince John's actions and Sir John Falstaff's behavior?