In Julius Caesar, how does too much ambition lead to disaster?
Ambition leads to disaster for Caesar, Cassius and Brutus because they all die as a result.
Julius Caesar was killed by a conspiracy of senators because they felt that he was too ambitious. Caesar marched on Rome and defeated Pompey, the former Roman Consul. Many senators felt that he had over-reached his authority. They worried that he was setting himself up to be king, and wanted to stop him before he had so much power that he was unstoppable.
Brutus explains to the people in his funeral speech that Caesar died for his ambitions.
As Caesar loved me, I weep for him;
as he was fortunate, I rejoice at it; as he was
valiant, I honour him: but, as he was ambitious, I
slew him. There is tears for his love; joy for his
fortune; honour for his valour; and death for his
ambition. (Act 3, Scene 2)
As far as Brutus is concerned, Caesar deserved death and they are heroes for killing him. He wants the people to feel the same way. Unfortunately for him, Mark Antony gives a speech after Brutus where he calls Brutus and the other conspirators killers. He whips the crowd into a frenzy, and they drive the conspirators out of Rome.
Brutus and Cassius did not give up. They attempted to defeat Mark Antony, now allied with Caesar’s heir Octavius (and Lepidus). Raising an army with their own funds and promises of riches, they take on the triumvirate. However, ambition again results in disaster. Brutus and Cassius can’t agree on anything. There is infighting within their ranks. They end up committing suicide. Cassius thinks he is defeated and kills himself, and Brutus kills himself when the battle is lost.
Despite the fact that he has been fighting Brutus, Antony gives an interesting speech in which he refers to him (not Cassius) as noble.
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. (Act 5, Scene 5)
Based on this, Antony (or Shakespeare) feels that Brutus was acting nobly. This does not mean that he was not ambitious though. You can be noble and still take on too much. Brutus’s goal was to restore the Roman republic, but while that may have been a noble goal it was too ambitious and destroyed him.