How is Shakespeare's play Julius Caesar ironic?

In Julius Caesar, Shakespeare gives his audience a masterful lesson in the variations of irony in literature. The plot is rich in situational irony, and scene after scene illustrates the effectiveness of dramatic irony. In Antony’s funeral oration, the power of verbal irony is manifested as he contemptuously praises Brutus and the conspirators again and again as “honorable men,” turning the Roman citizenry into a mindless mob set on vengeance.
Just as life is filled with ironic situations and outcomes, so is the play. Brutus must commit dishonorable acts in order to preserve his honor. Caesar can defeat his enemies on the battlefield, but he fails to recognize his greatest enemy—his own ego. He trusts most those he should trust least, and he rebuffs those whose advice would have saved his life. Cassius cleverly manipulates Brutus into joining the conspiracy and then discovers he is powerless to manipulate or even influence Brutus after Brutus commits to murdering Caesar. Cassius believes the conspiracy cannot succeed without Brutus, only to be destroyed by Brutus’s disastrous decisions. Instead of preserving freedom in Rome, Caesar’s assassination creates civil war and a political power vacuum that is filled by an ambitious, self-serving Antony.
Since the audience already knows how Caesar died and who killed him in 44 B.C., the entire play is infused with dramatic irony. In two particular scenes, the dramatic irony is developed at length, emphasizing the deception of those caught up in the political intrigue of Caesar’s assassination and its aftermath. In Act II, Scene ii, when the conspirators come to Caesar’s house to escort him to the Senate, the audience, knowing their intent, watches as they play on his ego and ambition and as he finally succumbs to their manipulation. Preparing to leave for the Capitol, Caesar, in good humor, tells the conspirator Trebonius to stay near him in the Senate. “Caesar, I will,” Trebonius replies,” adding in a chilling, ironic aside, “And so near will I be / That your best friends shall wish I had been further.” After Caesar’s murder, the audience knows Antony’s hidden rage and his secret intent to “let slip the dogs of war” to avenge Caesar’s death. Thus the drama in Act III, Scene i, when Antony shakes the bloody hands of the conspirators and receives permission to speak at Caesar’s funeral, is intensified.
Driven out of Rome into Greece and battling the armies of Antony and his ally Octavius, Brutus and Cassius endure a final—and fatal—irony, each committing suicide in the mistaken belief that they have lost the war. The final irony in the play, however, is reserved for the victorious Antony and Octavius. Standing over Brutus’s body, Antony praises the character of the conspirator he once hated, and Octavius declares that the virtuous Brutus will be afforded the “respect and rites of burial” that an honorable soldier deserves.