The Rise of the Conspiracy
The first scene of the play depicts the conflict between Rome's Republican past and Caesar's ascendance. The commoners march in celebration of Caesar's victory over Pompey but the Tribunes scold them and chase them off, arguing that Pompey was a celebrated Roman too so Caesar's triumph is not truly a triumph for Rome. As Caesar is loudly cheered by crowds offstage, we see Brutus admitting to Cassius that he is worried about what's happening to the Republic.
The conspirators present themselves as motivated by a desire to save the Roman Republic and overthrow tyranny, but the play teaches us not to take their claims at face value. We see Cassius's manipulation of Brutus, and the tortured logic of Brutus's reasons shows how out of touch with the truth he is. We see the conspirators betray and stab Caesar to death.
After the Assassination
After the assassination, the conspirators' survival depends on their ability to convince the populace and the other senators of Rome that what they did was for the sake of the Republic. As Cassius points out, in order to control how their actions are understood, they must either kill or at least silence Mark Antony, Caesar's loyal and powerful friend who is likely to speak against them.
The climax of the play comes when Antony, by juxtaposing Caesar's accomplishments, his generous will, and his corpse's brutal wounds with the repeated statement that “Brutus is an honorable man,” persuades the people of Rome that Brutus and his co-conspirators aren't honorable at all. Brutus and Cassius are forced to flee Rome and the country is plunged into civil war
The Downfall of Brutus and Cassius
When Brutus and Cassius meet in Act IV, at the head of their armies, and begin arguing with each other, we can see that they're doomed. Both of them have weakened their own cause by continuing to display the same flaws each exhibited in the early acts. Cassius has acted out of self-interest and now has angered Brutus by selling important offices for personal gain and refusing to send Brutus funds to raise an army. Brutus continues to be crippled by the delusion that he is more honorable than other people.
Analysis
Julius Caesar tells the story of how a dictatorship replaces a Republic, and how the actions of the conspirators only serve their own interests rather than the good of Rome. The play also highlights the power of persuasive speech and the dangers of delusion and manipulation. It shows how Brutus and Cassius's failure to reconcile their personal flaws leads to the downfall of their cause and the tragic end of the Roman Republic.