Shakespeare's play, Julius Caesar, begins during the Feast of Lupercal. Caesar is a strong military leader and respected ruler in Rome: he wants to become king. However, he has many enemies as well. Cassius is one. He wants to assassinate Caesar and tries to get Brutus, a man wholeheartedly dedicated to the good of Rome, to join Cassius and other conspirators in this plan, even if he must convince Brutus dishonestly. (Brutus comes to believe that Caesar would harm the empire.)
A soothsayer warns Caesar to beware of the "ides of March" (March 15), but Caesar ignores the warning. Cassius resents Caesar on a personal level because Cassius had once saved the emperor's life, but has not been rewarded for this act. His jealousy and resentment fuel his need for revenge.
Brutus is not quick to agree, but eventually joins the other conspirators, stabbing Caesar to death on March 15. Mark Antony is one who loved Caesar, and though he pretends to be open to explanations of why Caesar had to die (from the conspirators), he secretly promises to kill all of them. Brutus addresses the Roman people, explaining whey Caesar had to die, and at first they are supportive. However, at Caesar's funeral, Mark Antony gives a grand speech that makes the people rise up against Brutus and the other conspirators, including Cassius. In light of this divide of the nation's people, civil war erupts.
Antony, Octavius and Lepidus are to rule Rome as the new Triumvirate. In Act Four, scenes one and two, they all agree who must be killed when they take over to guarantee an easy transition. Lepidus agrees to kill his brother if Antony will agree that his nephew can be killed. If this isn't enough to question the ethics of Antony, he also arranges with Octavius that Lepidus will be excluded because he is old, but is useful for the moment to run "errands."
"This is a slight unmeritable man, / Meet to be sent on errands" (IV.i.12-13)
Eventually it seems that Brutus and Cassius (who have escaped to Greece) will have to fight the army of Antony and Octavius. When it seems that they have lost, Cassius covers his face with a cloth and pleads with his servant to kill him. Brutus goes into battle twice. After losing a second time, he falls on his sword (committing suicide) rather than being taken to Rome as a prisoner. He was a man of his convictions, and killed Caesar though he loved him, for the ultimate good of Rome.
Antony even praises Brutus at the end, speaking to what kind of man Brutus was, and what he most cared about—not killing Caesar out of jealousy, but an earnest desire to protect Rome:
This was the noblest Roman of them all:
All the conspirators, save only he
Did that they did in envy of great Caesar,
He, only in a general honest thought
And common good to all, made one of them.
His life was gentle, and the elements
So mix'd him that Nature might stand up
And say to all the world: "This was a man!"
When the war is over, Antony and Octavius are the most powerful men in the empire.