Pompey the Younger is (no surprise) the son of Pompey the Elder. He is most notable in the play as a character who is prone to war, but guided by his reason and honor instead of his passion. Pompey the Younger is drawn into battle against the Romans because his father was one of Julius Caesar’s partners in the first triumvirate that ruled Rome. Julius Caesar’s whole "crossing the Rubicon" bit was an act of war and usurpation against Pompey, and the decisive act that meant Julius Caesar intended to rule Rome alone. As a result of Julius Caesar’s action, Pompey the Elder fled to Egypt, where he was murdered. This is where his son, Pompey the Younger, steps in. He seeks to avenge his father’s death against the new triumvirate: Octavius Caesar, Antony, and Lepidus. Pompey ends up being a sort of sacrifice in the play. He's an honorable man who plays by the rules and is ultimately vulnerable to the treacherous and passionate men that surround him.
Pompey is well-loved by the people, and he sees Antony’s absence as a good sign that he has a chance against the other young triumvirs. Still, even once Antony returns to the fight, Pompey faces his fate nobly. One of Pompey’s single most telling acts is his willingness to negotiate with the Roman triumvirs before he goes to war with them. In the negotiation, he would rather compromise than have blood shed, not because he is a coward, but because he is a reasonable man.
Once Pompey settles the terms of compromise with the triumvirs, he graciously invites the other men back to his barge to celebrate their new truce. Unlike Caesar and Antony, when Pompey makes a truce, he means it. He has a real warrior’s honor, in contrast to the triumvirs, who would probably shoot him in the back in a dark alley. On Pompey’s barge, his man Menas offers to kill the drunken triumvirs, but Pompey’s honor again gets the better of him. He says he wishes Menas had simply not told him of the plan and just carried it out instead. Now that he’s heard about it, his conscience has gotten in the way. Unfortunately, Pompey ends up dead as a result of Caesar's treachery.